Fuel return line

[BakPak]

When I got home yesterday I could smell diesel and after a quick look it was dripping from front of the fuel line run under the driver's seat. It's fixed now by my local garage, used him for 10 years lots of different cars, he is a good mechanic.

He explained that the fuel return line had started leaking and when I saw this fuel line assembly going back and forth on itself I thought great how much? Anyway he simply replaced it with a straight piece.

I couldn't see a problem with doing that. Why does the diesel line do this, if it's to cool it why?

 

[BakPak]

Has anyone else removed this fuel line assembly and fitted a straight line?

Am I correct in thinking it's design is to cool the diesel? If that's right it just seems unnecessary to me!

 

[desertstorm]

You are correct it's designed to cool the diesel, In the summer when the engine is working hard the diesel could be returned to the tank at close on 90-100 degrees c. The fuel tank is plastic and doesn't like these kind of temperatures.
The other issue is that if the fuel volume is low in the tank when it gets there it will heat the contents up and this then makes it's way to the engine.Hot diesel is like hot air it takes up a larger volume.
So it has performance implications as the engine has to inject for longer to get the same effect.
On Common rail engines the diesel lubricates the pump etc, If it's very hot it can't take heat from the pump and won't lubricate the pump as well.
Audi don't spend money for no reason. It's the winter now so you should be OK,I would look into getting it replaced before the summer comes around

 

[BakPak]

Wow this is why I keep telling my mates how brilliant this forum is.

Thanks for the info dessertstorm I contacted audi earlier £231 + vat.

 

[desertstorm]

I would try and locate one from a car being broken. Not a part that would normally fail and I wouldn't have thought it would be too expensive. Nearly £300 from the dealers is daft.


Fuel cooler Audi A4 B6 1.9 / 2.5 TDi 8E0203572E New genuine Audi part | eBay


Karl.

 

[IanFM]

It might be worth talking to quattrojames on here as he is breaking a 2.5tdi just now.

 

[BakPak]

Do all audi's have this system or just certain models?

 

[S4_dan]

Do all audi's have this system or just certain models?

Not petrols, just diesels, 1.9 and 2.5 A4 B6