Some kind of Oil mixed in the Coolant tank....any idea?

[coco]

Hi guys,

I need a help!
My mechanic found some kind of oil in the coolant reservor tank.:nana:
Anyone has any idea?
What's the possible cause of the problem?
Please help.
Hope it's not serious problem....

Best regard,
Coco

[MaxRS6]

Possibly oil cooler issue

[coco]

Possibly oil cooler issue

Thanks, MaxRS6.
Is it the one located under a radiator? Part# 078117021D?
If it is, the coolant could get into transmission?

What should I do?

Does anyone has good thought on this?
Please help!!

Best regards,
Coco

[MaxRS6]

Here is a link about the oil cooler. It is a difficult part to get at for repair. I would get it to a good mechanic and probably not drive it until resolved. I certainly don't know if this is the root cause and just tossing out a possibility. I've had the oil cooler repair a couple of times.

http://www.audipages.com/Tech_Articles/enginemechanical/oilcoolerremovalreinstall.html

I did a search and also found a RS4 owner that posted he has oil in the coolant reservoir.

http://forums.quattroworld.com/rs4b7/msgs/81006.phtml

[mik15]

which oil cooler? i know a friend of mine had the same issue with an ML 63AMG and it was the gearbox oil cooler, i think it could be the same here...if so he should also change the gearbox oil as it has coolant in it now...definitely don't drive it anymore cause you can damage the GB and get the engine temperature too high and boil it!

[coco]

Here is a link about the oil cooler. It is a difficult part to get at for repair. I would get it to a good mechanic and probably not drive it until resolved. I certainly don't know if this is the root cause and just tossing out a possibility. I've had the oil cooler repair a couple of times.

http://www.audipages.com/Tech_Articles/enginemechanical/oilcoolerremovalreinstall.html

I did a search and also found a RS4 owner that posted he has oil in the coolant reservoir.

http://forums.quattroworld.com/rs4b7/msgs/81006.phtml

Thanks again, MaxRS6

I will talk about it to my mechanic tomorrow (it's almost 10 at night here in Japan).
We have vehicle inspection every two year here in Japan,a dn my RS6 is in the shop at this moment, so I won't drive until the problem will be solved.

Hope this is not a very serious problem.....

Best regards,
Coco

[905084]

If it is the oil cooler it is the whole cooler and not the the coolant pipe that connects the cooler to the block. You can see from the first link that MaxRS6 posted that the coolant pipe is separate from the oil passages. The oil/coolant can't mix there, just in the cooler itself if it is the cooler.

I don't know of any gearbox/engine coolant cooler that we have.

Any coolant in the oil? Should look like milk chocolate.

Don't drive it until you nail down what it is or at least confirm no coolant in the oil. Most likely the repair will start with "first, remove the motor"

[coco]

which oil cooler? i know a friend of mine had the same issue with an ML 63AMG and it was the gearbox oil cooler, i think it could be the same here...if so he should also change the gearbox oil as it has coolant in it now...definitely don't drive it anymore cause you can damage the GB and get the engine temperature too high and boil it!

Hi, mik15
Thanks for your reply.
But now you guys confused me.....
The oil cooler MaxRS6 told was the one on the engine itself that cools engine oil, right?
And the one you are talking about is the transmissiono oil cooler located below radiator?(#Part# 078117021D)

How the oil get into coolant reserver tank if it's transmission oil cooler?
Are they connected somewhere? I guess, they are not supposed be connected but located pretty close each other.
But somehow, gear oil and coolant mixed at somewhere.....
If that the case, do I need to replace the transmission oil cooler and flush the gear oil and replase with new gear oil, right?

I will talk to my mechanic about it tomorrow.

Best regards,
Coco

[coco]

If it is the oil cooler it is the whole cooler and not the the coolant pipe that connects the cooler to the block. You can see from the first link that MaxRS6 posted that the coolant pipe is separate from the oil passages. The oil/coolant can't mix there, just in the cooler itself if it is the cooler.

I don't know of any gearbox/engine coolant cooler that we have.

Any coolant in the oil? Should look like milk chocolate.

Don't drive it until you nail down what it is or at least confirm no coolant in the oil. Most likely the repair will start with "first, remove the motor"

Thanks 905084,

I will tell my mechanic about your suggestion.
Untike the U.S. and Europe, we don't have many C5RS6s in Japan (probably 100>), we don't have many machanics who knows much about RS6.
So, often times, we go tryal and error (Of course doing many research in RS6.com, too).
And parts for RS6 are EXPENSIVE in Japan usually 3 times more than in the U.S.!!

Hope they will find the problem quick and fix it nicely.

Best regards,
Coco

[MaxRS6]

^905084 is talking about the oil cooler- The same one in my post link. As he says, your issue will not be the coolant pipe- the entire oil cooler will need to be replaced if that is the issue. I provided the link to show the oil cooler. If the oil cooler has to come out, do the Bufkin tube at this opportune time during the repair/replacement.

[905084]

Only 2 things I know of that will put oil into the coolant:

A) Oil cooler is broken $$

B) Head gasket $$$$$

Might want to check the compression on all 8 cylinders. If one is zero, I'd lean to the head gasket.

[TozoM8]

1,) The oil cooler is a double jacket unit. Oil inside and coolant outside. If it has a hole, it will push oil into the reservoir because the oil pressure is greater than coolant pressure. However when you turn the car off there is no oil presure, but there 10-15 lbs coolant pressure that will push coolant into the oil.
2,) one of the trans cooler is integrated into your coolant radiator. Sometimes they brake into each other and the greater trans fluid pressure will push fluid into the coolant. With engine off you will have the same scenario as the oil cooler. If there is coolant in the trans you will need a rebuild. Coolant dissolves the clutch material realy fast.
3,) blown head gasket.

[NSU RS6]

I am trying to imagine the potential of this problem, and then multiplying by $3.

Makes ya want to squeeze your buttcheeks together.

[905084]

Ughh, I'm getting my coolers mixed up. Tozo is right.

I'm not sure the best way to test it. Compression test for the head gasket would be the easiest followed by pressure testing the radiator/trans cooler.

Followed by saving money, getting a third mortgage, maybe selling a kidney......

[coco]

Hi,
You guys really start scares me a lot in terms of $$$.

Anyway, Tozo's explanation had me understand the situation better, thanks.

Actually my car was running great until I brought it to check up for the vehicle inspection.
I felt no power loss nor no high oil and water temp even after driving really fast on highway......
Anyway, since we are middle of series of national holidays, I can't check if coolant is really mixed with either ATF or engine oil.

It sounded oil cooler problem is less $$ than trans cooler problem, right?
I cross my finger for that.

Best regards,
Coco

[905084]

Actually, oil cooler will be more $$ in terms of labor. Trans cooler is relatively easy (just the radiator). It will only be a third mortgage :)

[coco]

1,) The oil cooler is a double jacket unit. Oil inside and coolant outside. If it has a hole, it will push oil into the reservoir because the oil pressure is greater than coolant pressure. However when you turn the car off there is no oil presure, but there 10-15 lbs coolant pressure that will push coolant into the oil.
2,) one of the trans cooler is integrated into your coolant radiator. Sometimes they brake into each other and the greater trans fluid pressure will push fluid into the coolant. With engine off you will have the same scenario as the oil cooler. If there is coolant in the trans you will need a rebuild. Coolant dissolves the clutch material realy fast.
3,) blown head gasket.

Thanks, Tozo

Your explanation is easy to understand, thank you.

So the case 1) scenario, need oil flush and oil cooler replacement. Do the Bufkin pipe replacement at the same time (the aluminum pipe sold at e-bay, right?)
case 2), replace transmission cooler and trans rebuilt.... Is it possible to flush trans and replace with new ATF?
If not, should I do the T/C replacement with stronger T/C? Which is better? Anyone?
case 3) scenario, replace head gasket and do oil flash and replace oil filter and oil.

In each case, are there anything that I should do other than above?

Best regards,
Coco

[coco]

Actually, oil cooler will be more $$ in terms of labor. Trans cooler is relatively easy (just the radiator). It will only be a third mortgage :)

Hi, 905084,

Actually if that's the case, I might look for other RS6's on the market in Japan.
I drive 2003 burgundy w burgundy interior with 100,000km(=62,000miles) on it.
It is my 3rd C5RS6, actually.
100,000km is quite high in terms of used car in Japan. So there's not much resale value left in my car.

There are several C5RS6 with less than 30,000miles on them and sell for around $25,000.
And I'm also interested in Avant.

Trans rebuild will cost me around $11,000 here in Japan.
One brake rotor is $1,100 and front brake pad set is $800!!
I don't even think about trans cooler which is $990 in the US, right? Probably $3,000 in Japan.

Anyway, I have to figure out what really is the problem and figure out $$$ to fix it.
And then, if I will go ahead and fix the problem or look for other RS6's on the market.

I will update the situation.....

Best regards,
Coco

[905084]

Can always eBay....buyin' sellin'. To me it's about bang for the buck. If I had unlimited $$, I wouldn't be driving this. But this is the fastest thing I can afford, and I love it!

[coco]

Can always eBay....buyin' sellin'. To me it's about bang for the buck. If I had unlimited $$, I wouldn't be driving this. But this is the fastest thing I can afford, and I love it!

e-Bay price+S&H to Japan......
I hear you....if I have unlimited $$$$, I would keep C5RS6 and get C7RS6 (of course without DRC!!), hehehe.
I tried C6RS6, sure it has juice but I like C5 better somehow. I guess more fun to drive for me.

But the reality is that I have to deal with my financial situation like you do.
I am trying to figure out to save money to fix the problem.
If I take my car to an Audi dealer, they will rip me off badly.
I will get necessary parts from the US and have mechanic fix the problem.
That way, I will be able to fix the problem with the same $ as buying parts in Japan!!

Best regard,
Coco

[ben916]

My oil cooler was leaking coolant about a month ago.
The dealership did a pressure test on the coolant system and the oil cooler tube was cracked and there was a hole in the radiator.

Start with the cheapest first... do a pressure test on the coolant system...

[coco]

My oil cooler was leaking coolant about a month ago.
The dealership did a pressure test on the coolant system and the oil cooler tube was cracked and there was a hole in the radiator.

Start with the cheapest first... do a pressure test on the coolant system...

Thanks Ben,

I will talk to my mechanic about it next week after long weekend will be over.
So in your case, you replaced radiator and oil cooler tube?
No coolant got into your motor?

Best regards,
Coco

[905084]

You already know the coolant system leaks. There is oil in it. Unless it's not oil.

[Elevens]

If your Engine Oil is clean, I am pretty sure its your Water to Oil cooler. Somehow Engine Oil gets into the coolant system and not Vice-Verse, Probably due to Pressure differences. Bad news is that the Bentley Manuel Says Engine Removal in order to replace. Hope that's not the Case. Good luck...........................

[TozoM8]

One more thing. If you mixed pink/purple coolant with some domestic sh*t, it will turn into a brown sludge.

[ben916]

If your Engine Oil is clean, I am pretty sure its your Water to Oil cooler. Somehow Engine Oil gets into the coolant system and not Vice-Verse, Probably due to Pressure differences. Bad news is that the Bentley Manuel Says Engine Removal in order to replace. Hope that's not the Case. Good luck...........................

Yep, this was me

[905084]

Hmm, Tozo's point is very interesting. Drain your coolant, refill with genuine Pentosin and see what happens. Maybe no leak at all.

But even before that, do what Ben916 suggests and do that coolant test. If it doesn't leak, someone put some "domestic s#1t" in your coolant and you really have no oil in your system.

Refill, relax, enjoy!

[905084]

Pentofrost, not Pentosin. Yikes!

[lswing]

I wish I didn't know so much about Pentosin and Pentofrost...well it's good to know, but I really don't want to see them in my driveway again! Good luck with the repairs...

[905084]

Resolution? Inquiring minds want to know.