Coolant leak 2005 3.0

[mb32]

Was driving my 2005 A4 3.0 a few days ago when the low coolant warning light came on. I checked the coolant and discovered the expansion tank was completely empty. I topped the coolant off and checked for leaks but could not see any coolant leaking. I did replaced the coolant tank a few months back so I figured perhaps there was an air gap that I did not account for.

Today I noticed there was a pool of coolant leaking underneath the car. I visually inspected the coolant hoses, expansion tank and radiator for visible leaks with the car running and turned off but could not see any coolant leaking. It looks like it is leaking from the driver's side of the car.

I've searched and it looks like the coolant crossover pipe or the o-rings are a common source for leaks. I'm suspecting this may be where the coolant is leaking from since I cannot visibly spot leaks from the front of the engine and the crossover pipe is buried in the block galley. How costly to change the crossover pipe out? Is it possible I can just replace the o-rings or should I really look at doing the entire pipe assembly?

[SJorge3442]

Was driving my 2005 A4 3.0 a few days ago when the low coolant warning light came on. I checked the coolant and discovered the expansion tank was completely empty. I topped the coolant off and checked for leaks but could not see any coolant leaking. I did replaced the coolant tank a few months back so I figured perhaps there was an air gap that I did not account for.

Today I noticed there was a pool of coolant leaking underneath the car. I visually inspected the coolant hoses, expansion tank and radiator for visible leaks with the car running and turned off but could not see any coolant leaking. It looks like it is leaking from the driver's side of the car.

I've searched and it looks like the coolant crossover pipe or the o-rings are a common source for leaks. I'm suspecting this may be where the coolant is leaking from since I cannot visibly spot leaks from the front of the engine and the crossover pipe is buried in the block galley. How costly to change the crossover pipe out? Is it possible I can just replace the o-rings or should I really look at doing the entire pipe assembly?

If possible, pressure test the system. This will give the ability to pinpoint the leak location. The cross over pipes are difficult to access and require the removal of the intake manifold and associated parts. After that, you have a clear shot at the pipe. Some years had a plastic pipe, others had a metal pipe. I believe the only location containing O-rings is at the rear of the heads. Last I saw, those pipes were fairly cheap and I would probably recommend just swapping the pipe out versus dealing with the hassle of hoping the o ring swap works. I'm going to dig for a thread that highlighted this repair recently.

Edit: I can't find that post, but here is a shot of the cross over pipe. Its attachment point to the head is right there behind cylinder #3. The leak point with this pipe is sometimes the nipple that feeds the coolant heater throttle body.


Double Edit: The 2005 BGN MIGHT use a different hard pipe setup. I don't have the time now to dig into that, but something to note that the BGN has a different setup than the AVK engines.

[deyrag]

Don't have a good close up but you can see both ends of the crossover pipe and the o-rings along with the temp sender and the nipple the hose to the throttle body attaches to.

[john_gonzo]

Tada!

Go here to decode diagram numbers: 2005 3.0 Water Cooling

[AudiTLC]

necrobump-

I have a leak at the Y-connector to the upper radiator - coolant reservoir
on the diagram - labelled 35 (lower right)

However, the parts list only shows two hoses but not the actual y-connector fitting.
Anyone know the part # for this?
thanks

[john_gonzo]

I have a leak at the Y-connector to the upper radiator - coolant reservoir
on the diagram - labelled 35 (lower right)

However, the parts list only shows two hoses but not the actual y-connector fitting.
Anyone know the part # for this?
thanks

The y-connector is included in the hose part number.

8E0121101J .... Up to VIN 8E-5-125000
8E0121101AJ .... From sedan models from VIN 8E-5-125001, and cabriolet models from VIN 8H-5-005601

The VIN split is in the 2005 model year. ECS Tuning shows both parts but doesn't display the VIN split info until you've selected a model using "Shop By Vehicle".

[AudiTLC]

awesome, thank you so much for the info!

[EuroxS4]

Just be happy its that and not the hot plastic garbage they used for the rear coolant pipe between the heads and the valley. Earlier cars used a metal pipe instead of plastic. Just in case anyone ever has to deal with that garbage.

[AudiTLC]

I've come to realize Audi has embraced hot plastic garbage as a lifestyle.
#3to5yrleaselife

Just be happy its that and not the hot plastic garbage they used for the rear coolant pipe between the heads and the valley. Earlier cars used a metal pipe instead of plastic. Just in case anyone ever has to deal with that garbage.

[canonball]

I've come to realize Audi has embraced hot plastic garbage as a lifestyle.
#3to5yrleaselife

lol I love this