07 A6 FSI Engine Oil Cooler O-Ring Replacment
 

I posted this in the A6 C6 section under alternator removal since I was looking on how to remove the alternator to get at the oil cooler o-rings. I thought that I would post it here under a more appropriate title.

First I removed the belt tensioner to access the two bolts holding the alternator on.
Then I removed the 5 bolts holding the alternator bracket. Now I have access to the 4 bolts to the engine oil cooler.
Once removed I replaced the engine oil cooler O-rings which were very brittle and compressed.
The above steps do not mention disconnecting the power, all the hoses, wires and obstructions which made this a difficult and time consuming job.

I was able to replace the engine oil cooler O-rings from under the car (on jack stands). It would have been a little bit easier to access some of the hose clamps if I removed the passenger side engine mount, but I managed with the engine mount in place.

Prior to this job I was getting oil in the coolant but no coolant in the oil. When I removed the engine oil cooler I backed flushed it and a fair amount of crud came out. I verified that the engine oil cooler was not leaking internally.

I was also not getting much heat so I backed flushed the heater core with not much success. I did about 8 flushes of the engine with water to get rid of the oil residue before filling with coolant. With no success of getting hot air out of the passenger side, I added a tablespoon of PBW (powered brewery wash) used in the brewing industry to clean brewing equipment to the flush water. PBW is an environmentally friendly alkali cleaner safe for use on metals, rubber and plastic parts (I'm a homebrewer). When I used the PBW I started getting really hot air from the heater. I did one final flush with water before filling with coolant. With the crud from the engine oil cooler and the heater core being dirty, I noticed that the heat is much improved due to increased coolant flow.

Due to saving myself $$ by doing the work myself I was able to justify buying some new tools.
The first tool is a coolant air purge tool: https://www.ecstuning.com/b-schwaben...l/003466sch01/
The second tool is a hose clamp pliers: https://shop.advanceautoparts.com/p/...e+clamp+pliers
Both tools were a big help.

Overall I rate this job on par with replacing a timing belt (from my Acura) as far as difficulty.

Hopefully my Audi oil & coolant leaks are a thing of the past since I have previously replaced the oil filter o-ring, oil separator, throttle body adapter, PVC hose and valve cover gaskets.

Below are a few pictures:
1. After removal of oil cooler with original O-rings
2. oil cooler reinstalled
3. alternator reinstalled
4. New O-rings installed

https://cimg7.ibsrv.net/gimg/www.aud...4ddfdf1e2a.jpg
https://cimg8.ibsrv.net/gimg/www.aud...929cfd8cef.jpg
https://cimg9.ibsrv.net/gimg/www.aud...ba18c0ec0b.jpg
https://cimg1.ibsrv.net/gimg/www.aud...9b63f9e145.jpg

I am not convinced that my oil coolant issues are resolved. I will need to drive the car for a week or two to see if oil is present in the coolant reservoir.

My gut tells me that there may be a hairline fracture in the engine oil cooler that didn't show up when I tested it for leaks with water. The design of this engine oil cooler would not leak oil in the coolant from worn out O-rings since the coolant side is opposite from the oil side.

If the engine oil cooler is bad at least I know the routine to replace it.

Update:

I used a bottle of K-Seal in my coolant which solved my oil in the coolant problem.

After testing/driving the car, I discovered that the heater control valve was faulty (no heat on the passenger side, little heat on the drivers side). I replaced the heater control valve and all is working great again.

Makes me wonder what component/sensor is due to leak next.

Thanks ...considerably....great approach to getting at everything without ripping out half the engine compartment...especially the removal of the alternator bracket. I'm def going that route.

Glad that I could help.

Update, I replaced the (4) variable timing o-rings as they started leaking badly at 140K miles. The ones near the valve covers make it appear that the valve cover gasket is leaking.