Cabin filters are often neglected. And neglect can affect quality of the air inside your car and a very dirty filter can restrict airflow, causing you to be warmer or cooler than you’d like.

Here’s how to change the cabin filter.

Where is it?

VW moved the cabin filter from under the rain tray in the engine compartment to behind the glove box in the passenger cabin with the introduction of the 5th generation of the A platform cars. You can get to it by looking up at the glove box base in the passenger footwell.

Replacing the filter

Replacement is easy. All you need is a standard screwdriver.

There’s a piece of carpet in the top of the passenger footwell, between the glove box cover and the firewall. It’s held in place with two screws. Remove the screws and pull the carpet out.

Once you’ve removed the carpet, you’ll see a narrow piece of plastic that holds the filter in place. Slide it towards the passenger side door and it’ll come out.

Pull the old cabin filter out and slide in a new one.

Replace the plastic cover, and screw the carpet back into place.

You’re done!

Special thanks to TDIClub member btcost for both the vehicle and doing the actual work!

TDIs are sensitive to fuel quality. And the fuel filters on A5s, in particular, seem to require following a strict change schedule. Hard starting, loss of power, poor fuel economy—these are all symptoms of a clogging fuel filter.

As A5 TDI owners know, VW has flip-flopped on fuel filters for A5 platform TDIs. In this how-to we’ll help you identify what fuel filter your A5 uses, and step you through the filter change.

Which filter does my A5 use?

A5 chassis cars (2005.5-present Jettas) used three fuel filters. Two of them are, for all intents and purposes, identical, and one is different. Here’s the breakdown:

• 1K0 127 434: Used by early A5 cars, engine code BRM, with the last six digits of the VIN starting in numbers up to 83.
• 1K0 127 434A: Visually the same as the filter above, same applications.
• 1K0 127 434B: Used on late 2006 and 2006.5 A5 cars, engine code BRM, with the last six digits of the VIN starting in numbers higher than 83

Here’s where it gets a bit confusing. VW completed an additional production run in late 2006, probably to provide cars for sale during the 2007 model year, where no TDIs were sold in the US. At some point they re-started the counting on the last six digits of the VIN, so you can have a late 2006 car with a very low VIN (last six starting with 00 or higher). These cars also use the 1K0 127 434B late filter.

When VW introduced the CBEA engine in the 2009 Jetta, they went back to using the early fuel filter. The 1K0 127 434 and 434A filters will fit these cars, same as it does the 2005.5 and early 2006 cars.  HOWEVER, 2010 Golf TDI uses the late style filter.  There is a good thread on TDIClub, What Fuel Filter Do You Have?

If you’re in doubt about which filter your car takes, best bet is to remove the top of the filter canister according to the instructions below and take a look. The pictures in this how-to are of a 2009 CBEA Jetta, so it has the early filter. The tip-off is the 5 circle gasket in the cover, and the hole in the top of the filter.

Service interval

The recommended filter change interval on BRM and CBEA TDIs is 20,000 miles. Many BRM owners experienced symptoms of filter clogging much sooner than the 20K change interval, and have adopted the practice of changing the filter every 10K, when they change the oil. Fuel quality probably has a lot to do with filter life, so you may have a different experience based on where you purchase your fuel. It’s your choice.

Changing the filter

The filter sits in a large canister behind the passenger side headlight in the engine compartment. Start by removing the bolts on the filter canister cover (T27 bolts).

Carefully pry the top off the canister and move it aside, and set it on some towels to prevent fuel spilling.

Here you can see the 5 hole gasket that indicates an early A5 or CBEA fuel filter.

Pull the filter out of the canister. It will probably appear black. This is caused by some chemical change in ULSD when heated.

Once the top is off the filter canister, we recommend removing and draining the canister itself, as the action of removing the filter may dislodge debris that will remain in the canister unless you drain it. Contrary to some printed information, there is no drain on the bottom of the canister.

There are two 13mm bolts holding the canister in the car. Remove those and you can pull the canister out of the car.

Drain the fuel out of the canister for disposal.

With the canister out of the car, remove the 5 hole gasket and replace it with a new one, provided with the replacement filter

Place the new filter in the canister

There’s a large sealing ring on the canister top. Remove and replace the seal with the one provided with the filter.

Once you’ve put the new filter in the canister, bolted the canister back in place, and replaced the seals, you can replace the canister top. It will only go on one way: there’s a pin in the top and a hole in the canister to align the top.

Fit the top back on the canister and tighten the bolts. Note the bolts are quite soft and should not be overtightened. The seal will work: Don’t make them too tight.

One benefit of the A5 over the earlier cars is the in-tank lift pump will fill the canister. Cycle the key twice to make sure the canister fills, and start the car. It’s probably a good idea to keep the revs up around 2000 for 10 seconds or so to make sure the car doesn’t stall as it clears any accumulated air out of the fuel lines.

You’re done!

Remember to be sensitive to any loss in power or hard starting that may indicate a clogged filter. If you have persistent filter issues at a shorter than 10K change interval you may want to change fuel sources.

Special thanks to TDIClub member btcost for the car and the actual work!

VW TDIs are turbocharged engines with precise air metering. This means that the intake air has to be clean to protect the turbo and Mass Airflow Sensor. It also helps to keep moisture out of the air system where possible. And the airbox on a TDI should seal well to protect both against dirt and innacurate Mass Airflow readings.

Even though most folks agree that the manufacturer’s recommended 10,000 mile oil change interval is the way to go, there’s lots of debate regarding how often to replace the air and fuel filters in TDIs, especially CBEAs. Some people change air filters as often as every 10,000 miles, but most feel every 20,000 miles is a good interval. Whatever change interval you choose, the filter change is quick and easy. Here’s how to do it.

What will you need?

Air filter, part number 1K0 129 620 or 620A. The difference between these two filters is the number ending in the letter A includes a pre-filter. CBEA engines have a two part airbox that can draw air from inside the engine compartment if the snorkel to the outside is blocked. The prefilter helps keep moisture out of the engine when the airbox is accessing air from the engine compartment.

Many people decide to save a few dollars and forgo the prefilter. Whether or not you use one is up to you. However, we believe that all CBEA TDIs in North America were delivered with pre-filters. It’s your choice.

All you’ll need is a Phillips head screwdriver for this swap. Easy.

Changing the filter

There are a total of six screws on the top of the air filter box, four on the filter and two on the MAF connector. Remove the four airbox screws

Then remove the two screws on the MAF connector.

You can see all six screws in this top down view

Once the screws are out, lift the cover and remove the filter. Here you can see the old (20K) and new filters side-by-side.

If you look at the dirty filter you can see the line made by the partition in the airbox.

Put the new filter in place. It should fit snugly. Press the cover into place and replace the screws. You’re done!

A final note

Folks sometimes like to open their airbox to take a look at their filter to see if it’s time for replacement. This isn’t a good idea. Manufacturers maintain that the gasket on the filter is designed to seal—once. Technically, if you open the box you should replace the filter as it won’t seal as well the second time.

Anyone who’s done any research on VW TDIs know VW has some very specific oil requirements for these engines. And the requirements change with each new generation TDI. The ‘09 and later TDIs with common rail engines (Engine Code CBEA) require oil that meets VW’s 507.00 specification. Castrol has joint ventured with VW to create an oil for this purpose, and Total, Lubro-Moly, and some other refiners also have an oil that will work in this engine.

Many owners worry about the dealer or repair shop putting the correct oil in their TDI. The best way to be sure is to do it yourself! This how-to shows how easy it is to do on your own.

In this how-to we’ve changed the oil using the traditional method of removing the drain plug and draining the oil from the pan. Many owners prefer to use an extractor to pull the oil out of the pan through the dipstick tube. The CBEA can make this a little more challenging than earlier TDIs because of baffles in the pan. So we’re showing the old-fashioned way.

What will you need?

Pretty simple:

• An oil filter, VW Part Number 071115562C. These filters are made by Mann (VW OE), Mahle, and other makers
• Five liters of 507.00 oil
• A new drain plug or crush washer for your existing drain plug

Some VW drain plugs have captive washers. Most folks recommend replacing them when changing the oil. Many owners have re-used them with no ill effects. It’s up to you.

You’ll also need the following tools:

• Torx wrenches (T25 & T27) to remove the lower engine cover
• A 19mm wrench (box, socket, or open ended—3/4″ will also work)
• An oil drain plan
• Water pump pliers or an oil filter wrench to remove the top of the filter canister
• A small screwdriver or pick to remove the O-rings from the filter canister cover
• Some paper towels to protect some areas of the engine compartment and clean up
• A way to get the nose of the car in the air: ramps, jack stands, or, best yet, a lift. Please do not use a jack to support the car, it’s not safe.
• Rubber gloves are really helpful, too, and plan on getting oil on your clothes. It seems impossible to avoid, at least for some of us.

Preparation

The oil should be warm and have circulated through the engine just before changing. Best way is to drive the car a few miles (5 would be plenty) to warm up the oil and make sure the impurities are in suspension. Don’t drive too much or the oil will be unpleasantly hot.

Draining the oil

Get the front of the car high enough in the air so you can reach under it and remove the lower engine cover. Once the cover is off and out of the way, put a drain pan under the oil pan. Use the 19mm wrench to remove the drain plug. Remember the head of the bolt is pointing away from the front of the car when you decide which way to turn it.

Remember the oil will flow rearward, make sure it isn’t going to miss the pan.

Once the drain plug is out, let the oil drain and turn your attention to the filter.

Removing the filter

Many VWs now have paper filter cartridges that live in a canister on the left side (towards the radiator) of the engine. This system makes changing the filter significantly easier and neater than removing a spin-on filter.

The canister has a black top, and what looks like a very large nut on top of it. It’s probably bigger than the sockets you have (about 35mm). If you have one that will fit, use it to loosen the top. If not, you can use a pair of water pump pliers to loosen the top.

Remove the filter canister top. There’s a wrapped line in front of the canister that’s covered in heat insulation. You may want to protect that from drips by covering it with a paper towel.

Once the top is off, pull the filter out of the canister. You may want to have a plastic bag available to put the filter in as soon as it comes out to reduce dripping

Sometimes the spindle on the filter will break off in the canister, as it did in the center of the picture below. If it does, you’ll have to remove it with a pair of pliers. Some people also like to use an extractor to remove the last bits of oil from the filter canister.

Once the canister is clear of the old filter, including the spindle, you can put the new filter in place. It’s pretty easy to get right side up as the spindle points down.

Open the o-ring that came with the filter and replace the one on the canister top. Put the top back on. Tightening torque is very little, about 8 ft/lbs. You really don’t need to make it more than barely hand tight. The gasket will do its job.

Putting it back together

Replace the drain plug. Torque spec is not a lot, about 12 ft/lbs. Remember the pan is aluminum and you don’t want to damage it.

Be sure you’re using the right oil

Put 4 liters in the car, check the dipstick. A5s have what we think is one of the world’s most confusing dipsticks, so you may want to consult your owner’s manual to be sure of the correct level

Once the car’s buttoned up and at least 4 liter of oil is in it, start it up. Check for leaks. Shut it off and check the oil. If the nose of the car is in the air, don’t fine tune the oil level until the car is level.

If you’re satisfied that you’re leak-free, replace the lower engine cover and put the car on a level surface. Let it sit for a few minutes and then check the oil. Add oil as needed. You should have about ½ liter left when you’re done.

Congratulations!

Many of us changed our own oil when we were in our teens, but have gotten away from it as work, family, and other demands (or lack of a place to do it) got in the way. It’s one of the simplest things you can do for your TDI. And it’s rewarding to know that you’ve done it right with the right spec oil.

Changing Injection Quantity (IQ) is easy. Here’s how to do it.

Cable/Software/Port Setup

This how-to assumes that you’ve got your VAG-COM, downloaded the software, and made sure your car can connect to your computer. If you haven’t done this yet, www.ross-tech.com has detailed instructions.

Checking and Changing IQ

You car has to be running to get an accurate injection quantity reading. And it has to be up to operating temperature. So it’s best to drive the car for 20 minutes or so, some of it at highway speeds, to make sure you’ll get a good reading. You should not run your A/C during this test, as it will affect readings.

The screen prints in this article are from a 1997 VW Jetta TDI. If you have a different TDI some of the data displayed may be slightly different, so keep that in mind as you proceed.

You’ll first see this screen:

This is where VAG-COM launches. Click on the button named Select under the the words “Select Control Module.” Next you’ll see this screen:

All the engine control modules are listed, even if your car doesn’t have some of them, such as ABS. Click on 01-Engine to proceed and you’ll see something like the following screen:

The engine data will take a moment to populate. Newer cars populate faster than older ones (slower ECUs). Once the screen is populated, you can click on Login-11 to first login:

Type the numbers 12233 into the box to the right of the words Enter Code and click on Do It! This will take you back to the Engine screen:

This time click on the button Adaptation – 10. Next the screen below will appear:

However, you’ll see channel 00. Click the Up button to Channel 01 and you’ll see Adaptation numbers.

At the top of the screen you’ll see RPM and Injection Quantity. The IQ will most likely be a number between 1.0 and 3.0.

Next, look at the numbers on the left side of the screen. Below the Channel window you’ll see two boxes, one titled Stored Value and the other titled New Value. The default stored value is 32768. If your IQ has been previously adjusted you may see a different number. There’s a limit on the number range for IQ, it varies by ECU, but is approximately between 32645 and 32786.

The IQ measurement numbers are slightly counter-intuitive. A higher Injection Quantity (such as 3.0), will flow less fuel than a lower quantity (such as 2.0). And a lower new value (such as 32725 instead of the default 32768) will flow less fuel than a higher new value.

Why change Injection Quantity?

If your car:

• Smokes more than you want
• Shudders at slow down or idle

You may want to reduce fueling (increase the IQ number)

If your car is low on power, you may want to increase the IQ number.

Changing IQ

Here’s how to do it. On the adaptation screen, shown below:

Click into the New Value box and type in a new number. If the stored value is 32768 and you want to reduce fueling, try a lower number such as 32750 or 32725. Click on Test at the bottom of the screen. The IQ number will change (and your engine tone will change, too). Look at the new Injection Quantity at the top of the screen and see if it’s what you want. You can further adjust the IQ by typing in a new number and clicking on Test, or by using the up and down buttons to the right of the New Value box.

Once you’re satisfied with the IQ and want to test drive the car to gauge results, click on Save at the bottom of the screen:

You’ll be asked, Are You SURE?

Click on Yes to save the new setting. If you want, you can drive the car with the computer hooked up to determine if you’ve achieved the result you were after (more power, less shudder), and further adjust the IQ if needed.

Once you’re satisfied, click on Done, Go Back at the bottom of the screen, Back on the engine screen, and Exit on the main screen to exit VAG-COM.

Done!

One of the most basic VAG-COM uses is checking timing after a timing belt change. We’ll walk through that process here. In addition, adjusting your timing to be slightly (or more) advanced can improve cold starting, accelerator response, and fuel economy. So there are a lot of good reasons to have your timing set properly.

Here’s how to check.

Cable/Software/Port Setup

This how-to assumes that you’ve got your VAG-COM, downloaded the software, and made sure your car can connect to your computer. If you haven’t done this yet, www.ross-tech.com has detailed instructions.

Checking Timing

You car has to be running to check the timing. And it has to be up to operating temperature. VAG-COM also measures fuel temperature, and will provide slightly different readings if the fuel is cold. So it’s best to drive the car for 20 minutes or so, some of it at highway speeds, to make sure you’ll get a good reading.

The screen prints in this article are from a 1997 VW Jetta TDI. If you have a different TDI some of the data displayed may be slightly different, so keep that in mind as you proceed.

You’ll first see this screen:

This is where VAG-COM launches. Click on the button named Select under the the words “Select Control Module.” Next you’ll see this screen:

All the engine control modules are listed, even if your car doesn’t have some of them, such as ABS. Click on 01-Engine to proceed and you’ll see something like the following screen:

The engine data will take a moment to populate. Newer cars populate faster than older ones (slower ECUs). Once the screen is populated, you can click on Basic Settings-04 to see the timing data, shown below:

When this screen appears you won’t see the blocks with timing data as shown above. Hit the Enter key on your laptop for this data to display, or click the Up button under the Group label to Group one, and then click back Down to Group 000 to display the timing.

The data you’re after is in Block 2. In the sample screen it shows a timing setting of 64. Although the measurements vary by vehicle, this timing is advanced but within spec for most TDIs. If you want to see a graph click on the TDI-Timing button on the lower right of the screen and you’ll see the following:

This screen shows several pieces of data.

• The Red, Blue, and Green lines show the limits of timing within spec, from most retarded (red), to normal (blue) to advanced (green). The yellow line shows how the timing is set on your car. In this example it’s advanced, but within specifications.
• You’ll see fuel temp in the lower left of the screen. It shows 95F here. If the fuel is too cold you’ll see a warning message at the bottom of the graph.
• Also at the bottom of the graph you’ll see Result. In this case it says Timing within spec slightly advanced.
• However, on the right side of the graph you’ll see a drop down box where you can select the engine that most closely matches your car. And in this case you can see a 1.7l R4 SDI selected, not the 1Z/AHU that an A3 Jetta has. So the graph is calibrated for an engine different than the one in the sample car. You should choose a graph that most closely matches your engine (which we failed to do here) to get the most accurate data on your car’s timing

What do I do with the data?

As previously mentioned, timing settings can affect starting, power, and fuel economy. And timing that is way off can potentially damage your engine.

If you don’t see any data on the graph, or if your timing number is over 150, your timing may not have been set properly when your car was serviced. Your timing belt may be off at tooth, or even two.

The ECU will do its best to correct timing issues when the engine is running over 1600 RPM. Since the timing measurement is taken at idle, you won’t see any ECU correction in the screens above. And the ECU cannot compensate for retarded timing in during a cold start.

Correcting Timing

In rotary pump cars, timing should be set mechanically, not in VAG-COM. Tuners will fine-tune timing in VAG-COM, but it’s generally accepted that the best way to set timing is by changing pump position (1Z and AHU) and the pump cam (ALH). Timing can be fine-tuned in VAG-COM in Pumpe Deuse TDIs, which will be the subject of a future article.

Choosing between a stock or bigger turbo

Deciding whether to replace your turbo with another one just like it or to upgrade can be a complex decision. Or, it might be easy, because there may not be a larger turbo available that will easily fit your TDI. If there are upgrades available for our car, you should consider:

• A bigger turbo may not provide more power unless you make other upgrades (chip tuning, more fuel, better breathing)
• Bigger turbos may require supporting hardware for an easy install that can add to the replacement cost
• With larger turbos many expensive modifications may be required to take full advantage of the turbo’s potential

For example, a VNT-17 on an A4 TDI is a solid, well known upgrade. But it requires a $200 hose or a $100 adapter to fit stock intercooler piping. And bigger injectors (about $300), a chip tune ($300-700+), downpipe ($300-400), and improved intake (costs vary) are required to take full advantage of the power it supplies. And of course you’ll need a clutch. So you can see that choosing a bigger turbo is just the tip of the iceberg.

Many people consider a bigger turbo in hopes of improved reliability. And there are situations, even in stock cars (such as high altitudes) where a bigger turbo may last longer than the OE turbo, so this is a valid consideration.

Limited selection for some TDIs

For some TDIs there are very few options. For others, there are many. Let’s deal with the ones where choice is limited first.

• A5 Jetta, engine code BRM: Your option right now is a stock replacement turbo from VW, or a custom fabrication of manifold and turbo. No plug-and-play turbos that fit this car are in the US aftermarket—yet. With the A5 VW switched the turbo configuration to a top mount (the turbo sits on top of the manifold, not hanging below it as in earlier cars), so turbos from other TDIs won’t fit.
• B5.5 Passat, engine code BHW: This TDI has a separate turbo and manifold. Although there are probably many turbos that can be made to fit, the VNT-17, or Garrett 1749VA, is the only true plug-and-play option that’s readily available. Fortunately this is a great turbo, makes good power, and fails infrequently.



• A3/B4 TDIs, engine codes 1Z and AHU. These early TDIs had wastegate turbos in the US, not the variable vane turbos that are on all later VW TDIs. These two engines are nearly identical, but the 1Z has a Garrett turbo, the AHU has a Borg-Warner. The turbos are interchangeable. Like the B5.5 Passat, these turbos are separate from the manifold. There are other options for these cars including hybrid turbos with larger internals (plug-and-play), and switching to a VNT-15 or larger variable vane turbo (not plug-and-play).

A4 chassis TDIs, lots of options

On 1999.5-2006 A4 platform Golf, Jetta, and New Beetle, there are many turbo options. We’ll limit our discussion here to variable vane turbos with integrated exhaust manifolds. More than a few TDI owners have built their own manifolds, and there are also A4 TDIs out there with wastegate turbos. However, most daily drivers prefer the responsiveness of a variable vane turbo, and don’t want to go to the expense of building a manifold.

Stock Replacements

The ALH engined A4s (rotary pump) came with Garrett’s VNT-15 turbo. A version of this turbo started its life in the A3, but was first sold with an integrated manifold for the ALH engine. It’s very responsive, quite durable (especially if synthetic oil is used throughout its life) and makes great power. The dyno below shows what a VNT-15 can do with a chip and other supporting modifications. And when this dyno was run the turbo had 150K on it.

IBW dyno

The VNT-15 has benefited from running upgrades to vanes, internal metals, and other improvements during its life. It is less prone to carbon clogging (a common cause of failure on gently driven TDIs) than it was in the past. And many owners are out there with over 200K on their original turbos, so they do last.

When the Pumpe Deuse A4 chassis TDIs (engine code BEW) were brought to the US in 2004, VW switched from the Garrett VNT-15 to the Borg-Warner KP-39. This turbo is physically smaller than the VNT-15, but works exceptionally well in both stock and chip-tuned TDIs. 150 HP/240 lb/ft. is possible with this turbo and the right tune. The KP-39 does seem more prone to boost spikes than the VNT-15, especially in modified cars. And they also seem more stressed at high altitudes. Finally, some owners (again, in modified cars) have experienced boost creep at high speeds, eventually sending the car into limp mode. But these problems are neither that common nor catastrophic.

KP-39s just became available in the aftermarket. Because there was such a long delay before they were released, Garrett has made a version of their VNT-17 (1749VB) as a stock replacement for the KP-39

This turbo can be run in a stock BEW, but it also allows more airflow and can handle more boost than the KP-39. 165 HP/270 ft/lbs are possible with this turbo and the right tune and supporting hardware.

Want more?

For several years the VNT-17 was the upgrade turbo of choice for may ALH owners seeking more power. 180+ HP and 350+ ft/lbs are not uncommon.

Installing this turbo is fairly simple. The only major difference between it and a VNT-15 is the compressor (cold side) exit. The VNT-17 has a clip fitting that requires a VW hose or an adapter.

Unfortunately the hose runs about $200, but it allows the VNT-17 to plug right into most A4s. 1999.5 A4s will also need a new lower intercooler pipe, or charge tube, to accommodate the clip fitting at the intercooler end of the hose.

As mentioned above, the VNT-17 is also available as a stock replacement on the BEW, and is plug-and-play on that car. The turbo for the BEW includes a “smart” actuator that provides boost feedback information to the ECU.

Still want more?

If you’ve made other mods to your TDI including air handling (intake and exhaust) intercooling, fueling (bigger nozzles or higher pressure injection pump), and tuning and want more than the turbos listed above can provide, there are more options.

And although the VNT-17 is a popular upgrade on ALH engined TDIs, some drivers have found it less responsive (more lag) than the stock turbo. One way to reduce the lag and increase airflow is to use a larger compressor from a bigger turbo. This is how the 1752, or VNT-17/22, came into existence.

It is a VNT-17 with a compressor housing from a VNT-20. Because the larger compressor is spooling up a smaller exhaust wheel, it is more responsive than the VNT-17. Because it is made of components from two different turbos, it’s called a hybrid. And although its ability to make more maximum power than a VNT-17 is questionable, it does provide maximum torque sooner (lower revs) than the VNT-17 does in most setups. Here’s a dyno of the 17/22 in an ALH with many other mods.

Suppliers have also achieved this result by modifying stock VNT-15 housings to accommodate 17/22 or 18/52 internals. These turbos are available for both ALH and BEW engines, the only difference usually being the actuator. The BEW will usually require intercooler piping modifications for the hybrid intercooler pipe connections to fit properly, depending on the housing used for the compressor.

What to choose?

In summary, bigger turbos can mean more power. But sometimes they can jeopardize driveability with increased lag. Or they cause your car to smoke as they spool up, or cause you to need a new clutch to handle the increased power.

Best way to choose a turbo is to first identify your goal for increased power. Keep in mind that many tuners can improve HP and torque by 30% with a chip alone. Maybe that’s enough and you can stick with a stock replacement. But if you want more, happy shopping.

Related Products

Garrett VNT-15 Turbo (A4-ALH)
Garrett VNT-17/22 Hybrid Turbo (A4-BEW)
Garrett VNT-17/22 Hybrid Turbo (A4-ALH)

Filters can get clogged by old or dirty fuel. And even if you don’t have an incident of fuel filter clogging, replacing the fuel filter is part of your TDI’s 20K maintenance.

Where is it?

The fuel filter is on the passenger side of the engine compartment, just in front of the coolant overflow bottle. The one shown below has been in the car for 20K, but also for over 3 years because the car was stored for one year. It clearly looks like it’s ready for replacement.

The fuel filter has lines from the tank to the pump on the left, and a return on the right that goes through a thermostatic filter tee. The injection pump pulls fuel from the tank—there’s no in-tank pump on rotary pump TDIs—and also returns fuel back to the tank. Why? Because diesel fuel both cools and lubricates the injection pump, so it pulls more fuel from the tank than it needs to run the engine. The fuel tank becomes a big cooling reservoir to keep the pump cool.

The thermostatic tee helps the TDI work more effectively in cold weather. When the fuel is cold, it circulates fuel between the pump and the filter, only returning it to the tank once the fuel has warmed up. For some reason 1998 New Beetles did not have a fuel filter tee as original equipment, although they’ve been retrofitted to most cars.

Tools required

You’ll only need the tools shown below, plus a 17mm box wrench (maybe) to bleed the fuel lines.

Remove the fuel lines and filter

First, remove the fuel lines that come from the tank to the filter and the pump (the ones that don’t have the tee).

The filter shown here as OE clips. Often owners have retrofitted hose clamps. Once the clips are moved off the hoses, you can remove the fuel filter (or Mickey Mouse) clip, and lift the fuel filter tee out of the filter

Next, push the fuel lines off the filter.

The hoses frequently get stuck to the filter, and a little pressure with a screwdriver to break the hoses loose from the filter. Be careful not to distort or tear the hoses.

The filter is held in the car by a sleeve clamp with a v-shaped fitting that tightens down on the filter body with a Phillips head screw. Loosen that screw (shown at the bottom of the picture below) and the filter holder loosens up.

Sometimes the filter—like this one—gets rusted into its holder and has to be rotated back an forth a bit to free up and remove. The filter holds about a pint of fuel, so have a pan ready to empty the filter contents.

Preparing and installing the new filter

Remember, the injection pump pulls fuel from the tank to the pump and then to the engine. The pump cannot pull fuel from the tank if there is air in the system. Opening up the fuel lines to replace the fuel filter introduces air into the system. To limit the air in the system, you need to pre-fill the new filter before installing it. If you don’t do this the car will not run. The exception to this is ‘04 and later cars with an in-tank lift pump, or cars where the pump has been retrofitted.

You can pre-fill the filter with diesel fuel if you have it available, or any fuel additive, like Stanadyne or PowerService. Remember the fuel is circulated through the filter and back to the tank, so the additive will quickly be diluted with the rest of the fuel in the tank. Although it’s not essential, it can be helpful to have the fuel tank ½ full or more when replacing the filter, reducing the work the pump has to do when re-starting the car.

The filter media will absorb the fuel or additive. It’s worthwhile to fill it, let it absorb the fuel for a minute, and top it up.

Slide the filter back into its base, and tighten it down. Note the height of the filter in the holder.

Too high and the hood will hit it. Too low and the fuel lines to the pump will rub against the intercooler piping.

Next, replace the o-rings on the tee. These come with fuel filters, and are important to replace to prevent air leaks.

The pick is a good tool to remove the old o-rings, but if possible put the new ones on by hand to avoid damaging them.

Once the o-rings are in place replace the tee in the filter and insert the clip. Make sure the clip seats properly in its holder, shown below.

Air leaks can make your TDI hard to start, and limit the power it makes.

Restarting your TDI

If you’ve pre-filled the filter, and worked pretty quickly and therefore limiting the time for fuel to drain back to the tank, you may be able to re-start the car without difficulty.

Start the car and rev it to 2000-2500 RPM and keep it there for a minute or so. The engine will probably stumble as it clears air out of the system. But with luck it will smooth out and idle normally. It’s important to rev the engine on its initial start, because at idle it’s much more likely to stall and not re-start.

If the car does stall and won’t re-start, you may have to bleed the air out of the lines to the injectors.

With a 17mm box wrench, loosen the nut on the tops of #1 and #2 injectors.

Have someone crank the engine over until fuel sprays out of the fitting. Stop cranking the engine over, tighten the nuts, and start the car, once again revving it to 2000 RPM or so until it runs smoothly. Sometimes you’ll have to repeat this step, or also clear injectors 3 and 4.

Once you have the engine running smoothly check the clear fuel lines for bubbles. You’ll have some at first but as the car idles they should disappear. If they seem to persist re-check the filter tee to make sure it’s seated properly.

A clean fuel filter is an essential element to protecting your fuel system and allowing your TDI to deliver optimum power and economy. Regular changes will make sure your TDI runs smoothly and starts in the coldest weather.

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Where is it?

The air filter is easy to find on the driver’s side of the engine compartment. There’s a snorkel system that takes air from the grill and routes it to the airbox.

The only tools you’ll need for the air filter element replacement is a Phillips head screwdriver and either a cable hose clamp release tool or a pair of water pump pliers.

Remove the airbox top

First, remove the hose that goes from the airbox to the turbo at the airbox end. Be sure to hold the airbox top as you remove the hose. The airbox anchors aren’t very strong and can break if you put too much pressure on them.

Once the hose is off, you can simply move it out of the way.

Then, loosen and remove the two screws that hold one side of the cover in place

Once the two screws out you can tip the back side of the filter cover up and remove the cover. The filter is hooked to the front of the base, but tilting it up will release it. You can unplug the MAF electrical connection if you want, but it’s not really necessary.

Once the cover is off, take out the filter element. This image shows what a dirty filter looks like. This one has 20K on it. Once the filter is out, wipe or vacuum out the base of the filter box.

After removing new filter from its box, press it into the filter base. The filter will be a tight fit, and almost seem too big for the box. The gasket is quite flexible and will press into place. The gasket is designed to seal only once, so resist the temptation to repeatedly remove it and press it back into place.

Once the filter is in the box base, hook the front clips on the filter top in their location and gently press the filter top into place. Fasten it with the two screws.

Reattach the intake hose and you’re done.

This is a simple and quick maintenance process that you can do in a few minutes. And then your TDI and its turbo are set for another 20,000 miles.

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Objective

The objective is to remove the fuel lines at the fuel filter, insert a pair of adapters into the fuel lines, and feed those lines into the can of Diesel Purge. After that, the car is started and runs off the can of DP until almost empty.

Caution

2004 and later TDIs have an in-tank pump to provide fuel from the tank to the engine. You must disconnect power to this pump by either removing the relay or the fuse for the pump before starting the procedure. If you do not the pump will flood your engine compartment with diesel fuel from the tank.

Duration

From start to finish, the process should take approximately 30 minutes, including run time.

Procedure

1. Open the hood of the car, and locate the fuel filter, located behind the passenger side headlight.

2. Locate the two black rubber fuel lines that go to the injection pump. Using a pair of pliers or vice grips, squeeze and move the clamps back so that the lines can be carefully removed. You will need to move the clamps approximately 2 inches back on the line, so that they are no longer clamping the nipple on the fuel filter.

3. If the rubber lines do not want to move, even after moving the clamps back, use a special hose tool to remove the lines. If you do not have this tool, carefully nudge them forward with a flat blade screwdriver, being careful not to nick or cut the lines, or damage the plastic nipples on the fuel filter.

4. With the lines removed, insert one of the plastic fuel line adapters you received into each of the rubber lines.

5. Open the can of DP, being careful not to spill it. Place the two lines into the can, and put the can in a safe spot on the engine where it will not tip over. If you can have a helper hold the can, at least initially, that is ideal. Note that as you run off the can, the can will get HOT so make sure your helper is holding the can with a cloth or gloves. Ensure that the lines are at the bottom of the can, where they will not suck air as the can empties.

6. Go inside the car and start the engine. Let the engine idle for the next five minutes. After that, your goal is to run the engine through various engine speeds (RPMs). I like to run it for a few minutes at 1500rpm, then 2000rpm, and so on, going all the way up to around 3500rpm at constant throttle. I also let it idle down completely, then rev it back up to almost redline, then back down again. There is no right or wrong method here, simply vary the engine speeds and run until the can is almost empty (but NOT completely empty!).

7. Either your helper or you must keep an eye on the fuel level of the can, by peeking inside from the top. Since the can is made of metal, it can be hard to see, so some people like to first empty the can into a clear container, or bottle (such as a clean soda bottle). I find that I can tell pretty well when the can is empty, so I don’t find this extra step necessary, but it’s up to you. You should also make sure that the lines are always fully inserted into the can, almost touching the bottom.

8. When you’ve decided it’s time to stop, turn the engine off. Carefully pull the lines out of the can, and then remove the line adapters from each line. Careful, the can and remaining fuel will be hot.

9. You can now reinstall the rubber fuel lines back on the fuel filter, or go ahead and replace the filter, since you’ve done half of the labor already. If you do replace the fuel filter, you can pour the remainder of the DP in the can into the fuel filter, and prime the rest of the filter with diesel fuel, Stanadyne, or your favorite fuel additive.

10. Reinstall the lines onto the filter, make sure the filter bracket is secured (if you replaced the filter), and go start the engine. If the engine does not start immediately, it may take a couple of tries (if air is in the system). Crank for no longer than 5-8 seconds at a time.

11. When the engine is running, let it idle a while and then check for leaks. When you are satisfied that there are no leaks, go for a drive. You will notice that the engine is quieter, there is less smoke, and you may even notice more power!

12. You’re done!

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Disclaimer: TDI Blog technical tips are only suggestions on how to perform a task. You are responsible for following all normal safety precautions and factory procedures as detailed in the official service manuals. We assume no liability for your ability to perform these tasks. If you do not feel you have the skills to perform this task, visit a qualified mechanic instead. TDI Blog tech tips are copyrighted and cannot be reproduced or redistributed without our express written permission.