A4 PD BEW fuel cooling


Top Post Dawg
Aug 2, 2007
Chapin, South Carolina, USA
2005 A4 Jetta 5spd
IF this is on the 2005 wagon, then I would measure my fuel return flow. Ensure it is over 800 ml/minute at idle if you have a Bosch gear type tandem pump, ensure it is over 1000 ml/minute if it is the LUK tandem pump it came with.

Ensure someone has not crossed up the fuel lines. This causes low return flow with the pump hooked up, even if it has good return flow dumping into a bottle. It has happened before. Blue piping or marking is return flow lines. Pay attention to the arrows on the fuel pump assembly top that show direction.

Ensure your lift pump actually does pump. Hot wire it and you should get over 3 liters per minute from the pump into a jug.

Ensure the lift pump is actually running during engine run. Lift the seat and listen.

Lastly, a bad thermo tee on your fuel filter can cause temperatures this high.

Mk IV BEW fuel system testing. Look in post #7 for a link to a pdf.

Redneck Truck

Gone, but not forgotten
May 3, 2009
Plano, TX
2008 Touareg V10, 2001 Audi TTQ Roadster TDI 6-speed, 2005 Jetta Wagon TDI 6-speed
Fuel filter, therm t, and o-rings - new. Connections confirmed correct. Fuel temp still 90°C.

Removed and disassembled lift pump - screen almost completely blocked with what looked like dirt. Cleaned and reassembled and fuel temps have not exceeded 84°C under hard driving at 80 MPH on 70°F day.

Have a feeling I will need to recheck the screen several times, but very pleased so far with the outcome.

Cannot thank you enough for the time you spent experimenting and documenting and developing a knowledge base for this system. I will update you on future developments. Thanks again.