We had a customer come in with an R53 that had overheating problems. He was concerned that the head gasket was blown -- the coolant had engine oil in it. We did a compression test, and everything was fine -- the head gasket was sealed tight. We then pressurized the cooling system, and again found no leaks. But...the coolant was REALLY contaminated. We decided the only possible way this could happen was that the oil-to-coolant heat exchanger had cracked. I've seen this happen on other cars, but hadn't seen this before on a MINI.

If you're not familiar with this part, it's over on the passenger side of the engine block. It looks like this:



It's like an intercooler, but coolant is flowing through one side, and engine oil is flowing through the other side. Only the supercharged cars have this, by the way. As far as I know, the justacoopers do without.

We pulled the part off the car and pressure tested it on the work bench. Sure enough, it was leaking.

So, why didn't pressurizing the cooling system show us this leak? Perhaps because our pressure couldn't make it through this:



That's a picture of the radiator hose. The peanut-butter looking stuff is coolant, which has gelled from the oil contamination. The entire cooling system was full of it.

Some poured out on the belly pan when we opened up the radiator hoses and forced some pressure in...



Clumps plopped out into our drain pan...





We declared the radiator a lost cause -- the stuff was packed tightly into the tubes. For the rest of the system, we built a little setup we dubbed the Dialysis Machine. It's a pump we rigged up with a bucket of detergent mixture to flush the system out. We ran through about six buckets of the stuff before it finally rinsed clear.





So, an interesting case. I'm not sure what to take away from it -- I've never heard of this part failing before, and I have never, ever seen the coolant get SO bad. It was incredible how solid it had become, and how extensive it was throughout the cooling system.

--Dan
Mach V

 

What a mess!

So, the oil was in the water, but not the other way round? So you think the internally lubricated engine parts are still OK? Bearings and such?

I had a similar thing happen on an Audi, only it was the transmission cooler and the water went into the tranny fluid and ruined the transmission. I rebuilt it not understanding what had happened and a few thousand miles after I rebuilt it the tranny started slipping again. I finally found the trans cooler was the problem...........

 

Forum member and MINI tech Chadtoolio has encountered this condition and has devised this testing block to check the oil cooler's integrity.

 

This thread makes me want to puke.

Wow... that's pretty incredible, really...

 

The oil was clean. Oil runs as much as 100 psi at cold start, whereas coolant doesn't exceed 20 psi or so. So if the crack is small, the oil will exit more readily than coolant will enter.

--Dan
Mach V

 

Wow, that is just plain nasty.

You should maybe explain to your customer about checking the coolant once in a while...or at least bring it to you to check.

 

Good point... how did the coolant look in the reservoir? Same nasty mess, or clean?

 

that peanut butter is a textbook case of an 'emulsion'

if all that was bad on the car was the hose and the cooler, that guy should count himself lucky. could have caused a head issue he feared at the start from excessive heat.

 

I had an oil leak earlier this year (a small leak actually). Had the car flatbedded to Nashville and it turned out that it was this same oil cooler. At the same time I had been experiencing some tire vibration up front that may have contributed to the problem (my theory). Anyway I can tell you that looking for the source of the oil leak was a challenge. Very hard to pinpoint exactly where it was coming from.

 

That's a lot of gunk. >_<

 

Dan don't forget, once you shut the engine off , coolant pressure exceeds oil pressure then coolant can get into the oil. Just for peace of mind, I would change the oil and filter.

 

Guys as you may have seen elsewhere, this was the sight that i was greeted by yesterday. Dave at Thinkmini already suggested the Oil cooler when i told him over the phone what had happened.

Heres a pic. Car is thoroughly worked over GTT 260 and the engine was replaced back in february this year after the oil pump gave up and seized the bottom end at that time

 

Wow. That is freakin nasty.

How many miles on that car?

 

We definitely changed the oil and filter -- we'd do that in any case, as you said, for peace of mind.

Were you talking to me? Our customer's car has 63000 miles.

--Dan
Mach V

 

I need an warm fuzzy and I really don't want peanut butter oozing out of anything!
My 2004 S began leaking oil over the weekend. The oil light to blink first thing this morning. My mechanic tells me the oil cooler has 'blown' and it will be $600 to replace. Now, I'm a little flustered at this, but I can't tend to her needs myself. Being that I don't have the facilities or tools in my current location, is it worth the cost have the local wrencher fix it? Home is more than 1200 miles away right now and I would just like someone to tell me it's not a complete shafting. I'm sure this matters, she's a little over 157,000 miles now. "We drive the hell out of her" as my husband says.

 

That's pretty crazy stuff right there. Thanks for the pics and details, even if it was sorta disgusting!

 

Would a aftermarket oil cooler solve this problem?

 

That seems a little steep to me. The part can be had for about $136 from pelican parts, and the install shouldn't take more than 30 minutes. So I'd say less than $300 parts and labor.

It would prevent mixing and the formation of the peanut butter gunk, since it would separate the oil system from the coolant system.

 

Wow, that reminds me of chipotle sauce.

 

I don't beleive you can bypass the stock cooler w/o some fab work.

 

You gotta love NAM. I had a small oil leak Tuesday morning and put the car in the nearest shop. When I went to pick it up, the mechanic said they couldn't stop the leak, and showed me where it was (in the above-pictured part - we didn't know what it was). As he was showing me, the leak turned from a trickle to a flood. I'm glad I wasn't on the road when this happened. I got the car towed to Munchen Motors, a shop that works on european cars only. They said that though it appeared to be from the oil cooler, it turned out to be a bad seal on the oil filter. Apparently, not everyone knows this seal needs to be replaced every time the filter is.

 

Is this part of the oil filter housing?

Are there any aftermarket oil coolers that replace this part?

 

It's attached to it:



(The cooler is part 5 in the pic above. MINI calls it "heat exchanger.")

Not that I'm aware of.

Edit: My mistake, there ARE aftermarket coolers that fit in place of that core. They're not cheap -- they come with a flat plate to go in place of the heat exchanger, and then lines that run to a remote-mounted air cooling core.

--Dan
Mach V

 

Well after some more research I find out that just about all of the aftermarket oil coolers do replace this OEM part. But I couldn't find one with a thermostat.

 

What's involved if one wanted to remove the oil filter housing? I'm guessing that the engine might need to be out...