Another coolant in oil thread

A6 All/ S6 All
#1

I posted earlier in a thread that the Black Stone oil analysis showed possible coolant in the oil based upon sodium (215 v. 18 ave.) and potassium (20 v. 4 ave.) levels. Prior to this I had to add a small amount of the coolant to the coolant reservoir. I had thought it might be that I didn’t get all the air out of the system so it needed a top off. I was (and still will) send in another sample in to Blackstone to see if the numbers are higher.

Today when starting an oil change I noticed a small amount of that telltale chocolate shake residue in the oil separator when removing the vent hose (which broke from being very brittle…$200 part on order! >:( ).

So…now I have to decide how far I’m going to dig into this, which is where I’m looking for some advice.

I am set to do a carbon clean in April. I was also going to do a power steering drain and had intended on removing the bumper. At that point I guess I could remove the oil cooler and test for leaks for a half day more work. Foolishly did not think to test cooler when I replaced oil cooler o-rings. If the cooler turns out to be bad, I’ll just tell myself the failure occurred recently and I wouldn’t have found it then. New oil cooler is somewhat reasonably priced $267 on AudiUSAParts.com (again, stupid vent hose is ~$180 online, $208 at local dealer)

Beyond that, I’m not sure there’s anything else I can check without doing an engine drop and tear down, is there? There’s some tubes at the back of the engine that eng92 and gregoh pointed out, but those are buried inside.

EDIT: fixed sodium/potassium numbers

#2

Do you have the average levels transposed? My report and the sample reports on Blackstone’s site indicate averages for Potassium in the 3 to 4 range and the average for sodium in the 15 to 18 range.

How many miles were there on that oil sample and what antifreeze% did the report list?

#3

Thanks for catching that–yes, I did have the numbers switched.

For % antifreeze, the report says “POS.” Other than the meaning I am already familiar with ;D, what does that mean in this report?

Miles were 120,300.

#4

There are a lot of acronyms using “POS”, but I do not see any of them as being applicable in the context of an oil analysis.

I meant what was the OCI, not the mileage on the vehicle.

#5

OCI: 7000 miles

Comment in report: “these results do suggest a small amount of coolant contamination in the sample.”

#6

I would say you caught this very early on.

My potassium and sodium levels were roughly four times what yours are and the antifreeze% in the oil was given as 1.5%.

As Greg pointed out in another thread, if there was an internal leak in your oil cooler, you should find evidence of oil in your coolant. The oil cooler is the first component in the circuit that the oil goes through once it leave the pump outlet. When the engine is running, the oil pressure in the cooler will always be higher than that of the coolant. If there is oil in the coolant, you may see a film on the surface in your coolant reservoir. When a warm engine is shutdown, the pressure on the coolant side of your oil cooler will be higher as the oil gauge pressure will drop to zero once the pump stops.

You have such a small amount of coolant in your oil, if there is a leak in your cooler, it is very small and will be difficult to find using a simple low pressure air and wait for bubbles test.

Depending on your comfort level, this may be more of a monitor the condition through checking level drops in your coolant reservoir and further oil analysis. If the amount of coolant in the oil remains low and your wear metals do not increase significantly, I do not see that there is an immediate need to do anything drastic.

#7

Thanks for the good advice. Unless the next sample comes back with dramatically higher number, I’ll take a wait and see approach.

There’s a little bit of brownish crud in the reservoir, say 3mm above the surface around the perimeter–could be oil, I don’t know? Really not a lot. Coolant is low, so I’ll have to add a bit again.

Here’s the response from BlackStone re: “POS”:

“POS” means positive, and that is based on the amount of potassium and sodium in the sample. We can sometimes provide a % antifreeze based on the amount of sodium present. Sodium is also used as oil additive in some brands, and when that is possible we often will report antifreeze as a POS instead of a %. That was the case in your report. Coolant is the only normal source of potassium in a gasoline engine, and the 20 ppm in that report was just enough to make a positive call on antifreeze.

#8

Hard call. If you plan on doing a carbon clean and looking over the car later in the year and can stand do to without the car as a DD for a bit and you already did the oil cooler O rings It might not be a bad idea to test the cooler just for the sake of testing. These coolers are known for this kind of failure so it wouldn’t be out of the question.

I suppose you could always do the wait and see approach by monitoring the coolant but at the same time usually when things pop up they don’t always come at the most convent time. Still while your contents is low you have time to consider your possible plan for attack

The good thing is the levels are not at a you need to do something this second levels but its hard to tell how things will or wont advance.