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!