Mach 5

I have a '07 Audi Q7 3.6 that has some oil in the coolant. I can't seem to find much help on the Audi or VW forums, so I thought maybe my Cayenne brethren might be of some assistance (for those who may not know this, the Cayenne, Touareg, and Q7 are related, and all have shared the VW VR6 engine).

The car has 103K. The coolant light came on yesterday when driving on the freeway, but the temp remained constant and normal. Upon inspecting the coolant reservoir, I fount the telltale tan milkshake indicating oil had contaminated the coolant. The good news is that it does not appear that any coolant has found it's way into the oiling system, with both dipstick and oil fill cap appearing clean. A couple months ago, I did get a low oil warning light. I added about a quart of oil and all was good. The oil level has dropped about a pint since then, so I'm pretty sure I now know where the oil is going.

I'm suspecting the oil cooler. This would explain oil in coolant only. Versus mixing in both the coolant and oiling systems, which would lean more toward head gasket. I can't find any stories relating to oil cooler failures in Cayenne, T-reg, Q7s, but I have found several stories regarding oil cooler failures in other VR6 equipped cars. It's not a terribly expensive part, about $60. But I'm assuming it will be a pain to replace, plus flushing the system out to get all the oil residue out will be a pain as well.

I guess I have three questions;

1. Any other V6 owners experience this and what was your resolution?
2. Anyone have any experience in replacing the oil cooler? Any tips?
3. I know it was common 40-50 years ago to replace all the rubber hoses after oil contamination. Is this necessary with modern hoses?

Any help is appreciated.

Roger

PartsGuyGT

Based on your description, it looks like you're on the right track suspecting a bad cooler. We used to run into the same problems when I worked at a VW dealer. Although the only failures I saw were on the 1.8 and 2.8 cars, it wouldn't be uncommon to have a cooler go bad on a 3.6. The cooler might be tricky to access since it faces backwards towards the firewall on the Treg/Q7/Cayenne.

We used to flush out the cooling system until we saw clean water come out once the oil cooler got replaced. Refill with coolant, bleed and make sure you have heat. No hoses got replaced unless they looked really bad inside.

Mach 5

Yes, I was looking at it yesterday. I'm pretty sure I can easily loosen the cover. I think the real bitch might be loosening the clamps on the two coolant hoses attached to the cooler. They look like tension clamps that require pliers to squeeze them. Getting my hand up in there with pliers will be a challenge. It might be easier if they were just screw tight clamps. Oh well, I'll find out! Thanks.

Roger

PartsGuyGT

These pliers are a godsend for jobs like that. I'm sure those who have done T-pipes on CTT's have had to use them.
http://www.sears.com/craftsman-cable...p-00947390000P

-Julian

Mach 5

Awesome! I've been wrenching on cars for over 30 years and never knew these existed (probably because most of the cars I wrench on are also over 30 years old!). I ordered a similar set from Amazon, be here Friday. Thanks for sharing this.

Roger

Petza914

Got the Amazon link? Sears link shows NLA and no pic. Thanks.

PartsGuyGT

Mach 5

Here is the set I got, maybe not quite as good of quality as that Sears wrench, but I like having the set and a box for them.


Roger

Petza914

Thanks. Just ordered that same set to add to the tool arsenal.

nodoors

I have that exact set and they work well enough for me. They are helpful with many projects.

Mach 5

I replaced the oil cooler a few weeks ago, and unfortunately, that does not appear to be the source of the oil in the coolant. Been driving it some, still see a fair amount of oil in coolant, and the oil level appears to be down slightly. I also had an opportunity to pressure test the old oil cooler at 50 psi under water, and there are no signs of leaks. So, back to the drawing board.

Again, I really do not think it is a head gasket, e.g., no coolant in oil, coolant level does not go down, and car runs great. So, I am now thinking that maybe it is the water pump. I have read that sometimes these can allow oil to mix with the coolant. My questions for anyone with experience; 1) Does this make sense, that a water pump could cause this issue on the 3.6 engine? 2) Any other suggestions as to what might cause this?

Thanks.
Roger

deilenberger

1. Not that I can think of. No reason for oil to come anywhere near the water pump. It's not a combined oil/water pump like BMW used on some motorcycle engines. 2. No - Have you done an extended pressure test of the cooling system - if so - what were the results? (must hold XX-bar for XX minutes sort of test.)

It's not uncommon for oil to get into water and not have the opposite happen. If it's an oil feed passage to the head leaking into a coolant passage - the higher oil pressure results in the flow being in one direction. So you can't discount a head gasket. Has the engine ever been overheated?

Mach 5

No, I haven't pressurized the cooling system. I don't want to push water into the oiling system if I can help it.

No, the engine has never been overheated (we've owned since new).

Having looked at pictures of the oil pump, I also don't see how/where oil would get into the cooling system from the pump. I shudder at the thought of what the Audi dealer will charge for a head gasket. I'm guessing close to $3K. Next SUV will be Asian

Roger

Mach 5

Probably not related to the oil in coolant, but there appears to evidence of a valve cover gasket leak at the back of the engine. Again, I can't envision how oil and coolant passages would meet via a valve cover gasket, but I'm putting it out here.

Roger

Douglas61

thanks for sharing. Did you get it sorted out now?