Coolant in Oil - Help!
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Joined: Dec 2013
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From: Johannesburg, South Africa
2004 CLK 320 Coupé
Coolant in Oil - Help!
Hey Guys.
Me again. Hope you are all well.
So yesterday took the old 209 to my mechanic for a service. He opened the cap and showed me the mayonnaise type emulsion when oil and water mix.
We drained the oil and to be honest I couldn't see much contamination in the pan, but the oil filler neck and oil cap was but not heavily. he suspects that it is the oil cooler. According to him head gaskets on the M112 rarely gives.
Does this sound like a plausable diagnosis?
What do you guys recommend.?
If it is the oil cooler do I need a new one. Or can seals be replaced.
Remember I'm getting coolant in the oil and not the other way around.
Any help would be appreciated
Thanks Gents
Me again. Hope you are all well.
So yesterday took the old 209 to my mechanic for a service. He opened the cap and showed me the mayonnaise type emulsion when oil and water mix.
We drained the oil and to be honest I couldn't see much contamination in the pan, but the oil filler neck and oil cap was but not heavily. he suspects that it is the oil cooler. According to him head gaskets on the M112 rarely gives.
Does this sound like a plausable diagnosis?
What do you guys recommend.?
If it is the oil cooler do I need a new one. Or can seals be replaced.
Remember I'm getting coolant in the oil and not the other way around.
Any help would be appreciated
Thanks Gents
Senior Member
Joined: Jun 2016
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From: Bognor Regis UK
Alfa 159
Do you do lots of short journeys?...if you do you may not get enough heat into the oil to drive the water out. I always had the mayo on the oil cap of my Golf when I only lived a mile from work. I halved my oci.....which helped a bit. Send some old oil for testing...it's the only way to be sure...but you can usually smell the coolant in the oil. You need to find out soon though...coolant and bearings don't mix. Hopefully it turns out to be something minor and not too expensive.
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From: Atlanta Metro
2008 clk550 - Navigator - Frontier
I recently had my oil cooler gaskets replaced ($350 - $400). I had them replaced due to an oil leak under spirited driving situations. There was no contamination, just the leak.
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Ditto on CLK2000K's comments - not getting the engine up to temp and RPMs can allow condensation to form and cause that "peanut butter" coating on the filler cap. Are you losing coolant? Or, are there signs of oil int he coolant? If not, then I suspect some spirited driving may fix it. But your mechanic is correct - head gaskets rarely fail on M112 engines (unless they have been overheated, and warped, but that's a whole 'nother set of issues). The oil cooler gasket would be the suspect.
Thread Starter
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From: Johannesburg, South Africa
2004 CLK 320 Coupé
Strangest Thing
Thanks for all the replies guys, will definitely take everything into account,
Stranger thing, this morning drove about 20km's to the mall, opened the cap and saw the emulsion on the cap and little bit on the wall of the filler neck,
This afternoon, drove home, same 20km's(we went to watch suicide squad and have lunch, was at the mall for 6-7 hours)
Checked the cap immediately, nothing, absolutely nothing, looks normal,
Am I correct in that if this was the head gasket, I would have had mayonnaise emulsion all covering the oil cap and filler neck?
Another question, can the seals in the oil cooler just be replaced, or would I need a new unit,
Reason I'm asking is, based on the seals that I see, the seals you buy is actually just for the fitment of the cooler to the oil filter housing to seal that, but you can't actually replace the internal seals of the cooler,
Am I also correct in assuming that since I potentially have coolant leaking into the oil, that the internal oil cooler seals are broken, and not the seals between it and the housing?
Thanks for the help guys,
Stranger thing, this morning drove about 20km's to the mall, opened the cap and saw the emulsion on the cap and little bit on the wall of the filler neck,
This afternoon, drove home, same 20km's(we went to watch suicide squad and have lunch, was at the mall for 6-7 hours)
Checked the cap immediately, nothing, absolutely nothing, looks normal,
Am I correct in that if this was the head gasket, I would have had mayonnaise emulsion all covering the oil cap and filler neck?
Another question, can the seals in the oil cooler just be replaced, or would I need a new unit,
Reason I'm asking is, based on the seals that I see, the seals you buy is actually just for the fitment of the cooler to the oil filter housing to seal that, but you can't actually replace the internal seals of the cooler,
Am I also correct in assuming that since I potentially have coolant leaking into the oil, that the internal oil cooler seals are broken, and not the seals between it and the housing?
Thanks for the help guys,
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2006 E55, 2012 GLK350 & 1992 190e sportline
Are you losing coolant? Or, are there signs of oil int he coolant?
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CLK55 W209, CL63 W216
+1 on the short trips. It's a normal condition with most cars if you do lots of short trips. Keep an eye on the coolant level as well as the tank. Check for contamination in the tank. Wipe the cap clean and do a longer trip...and check again...for peace of mind 
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It sounds to me like there is no problem. But, if you do find it's the oil cooler seal, it is easy to replace - remove the oil cooler, pull the old seal off, put a new one one, replace the oil cooler.
Thread Starter
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Joined: Dec 2013
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From: Johannesburg, South Africa
2004 CLK 320 Coupé
I suspect something is starting to fail, I'm just not sure if its the seals on the out side, of internal oil cooler seals, drove like a maniac this morning to work, for about an hour, checked the oil cap and theres definitely mayo, on the cap, not a lot, so it looks like whatever is failing, is just starting to fail,
My only issue is, how do I determine what is failing, the replaceable seals, or the internal seals in the actual oil cooler, since it seems like a little coolant is leaking into the oil,
Thats my dilemma, :-(
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2006 E55, 2012 GLK350 & 1992 190e sportline
I have never heard of the oil cooler mixing the fluids. Normally a bad seal will have it leaking oil all over the place but that's it. Did you clean the cap before you went to work? If your not loosing coolant then it is not coming from the cooling system.
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From: Johannesburg, South Africa
2004 CLK 320 Coupé
So I'm really confused, what else would cause mixing of fluids if not the oil cooler? Head Gasket blown? but then I would have expected a greater amount of mixture,
What does experience tell you guys?
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2008 CLK550 Cab
Maybe you should clean the cap good, drive it 20 miles, and then post a pic of the mayo. People my have a better idea if they can see both how much and what looks like. I'm voting with the nothing is wrong crowd for now.
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From: Johannesburg, South Africa
2004 CLK 320 Coupé
Ok, I'll do that on my way home this afternoon, and post back to you guys,
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From: Johannesburg, South Africa
2004 CLK 320 Coupé
Not yet. Just changed oil 2 days ago. But I suspect a leak would have changed the fluid regardless.
In any event. I took a nice drive home. Opened the cap. And no milky slush at all.
So I'm leaning towards condensation for now. But is there any way of knowing for sure.
Coolant level looks the same. So will monitor for now.
My only concern is the different pictures throughout the last 2 days.
This morning after getting to work. Cap was milky. Drove to the garage. Came back. Cap was normal. Left the office for home. Checked the cap before I started the car. Cap was normal.
Get home. Cap is normal.
In any event. I took a nice drive home. Opened the cap. And no milky slush at all.
So I'm leaning towards condensation for now. But is there any way of knowing for sure.
Coolant level looks the same. So will monitor for now.
My only concern is the different pictures throughout the last 2 days.
This morning after getting to work. Cap was milky. Drove to the garage. Came back. Cap was normal. Left the office for home. Checked the cap before I started the car. Cap was normal.
Get home. Cap is normal.
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CLK55 W209, CL63 W216
Not yet. Just changed oil 2 days ago. But I suspect a leak would have changed the fluid regardless.
In any event. I took a nice drive home. Opened the cap. And no milky slush at all.
So I'm leaning towards condensation for now. But is there any way of knowing for sure.
Coolant level looks the same. So will monitor for now.
My only concern is the different pictures throughout the last 2 days.
This morning after getting to work. Cap was milky. Drove to the garage. Came back. Cap was normal. Left the office for home. Checked the cap before I started the car. Cap was normal.
Get home. Cap is normal.
In any event. I took a nice drive home. Opened the cap. And no milky slush at all.
So I'm leaning towards condensation for now. But is there any way of knowing for sure.
Coolant level looks the same. So will monitor for now.
My only concern is the different pictures throughout the last 2 days.
This morning after getting to work. Cap was milky. Drove to the garage. Came back. Cap was normal. Left the office for home. Checked the cap before I started the car. Cap was normal.
Get home. Cap is normal.
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From: Carrollton Texas
clk and e coupe
i agree on the condensation.
The best way to know is to keep an eye on the cap and or drain the oil in a few days and see what it looks like, also keep an eye on the coolant level, if it is mixing it will go down. But i think you are fine.
The best way to know is to keep an eye on the cap and or drain the oil in a few days and see what it looks like, also keep an eye on the coolant level, if it is mixing it will go down. But i think you are fine.
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From: Chicago area
2015 E400 and 2015 GLK350
I have had sludge form on the filler neck and cap of air-cooled engines. Where would they get coolant from? It was just condensation in that case, maybe helped along by a bit of blow-by due to high miles on the engine.
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From: Johannesburg, South Africa
2004 CLK 320 Coupé
Is that on the inside of the oil cooler, the only seals I've seen so far are the two small ones, one is round and the other is a slightly long oval,
Last edited by LordPhoenix; Aug 12, 2016 at 02:36 AM. Reason: Resized imaged
Thread Starter
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Joined: Dec 2013
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From: Johannesburg, South Africa
2004 CLK 320 Coupé
So I wiped the cap clean this morning, drove for an hour to work, getting motor completely up to temp and nice and hot, got to the office and opened the cap,
This is what I found:
So to be honest, I'm definitely suspecting a leakage, although very slight, so could be at the beginning stages,
What do you guys think,
Cant be condensation now, Drove this car hot for an hour,
This is what I found:
So to be honest, I'm definitely suspecting a leakage, although very slight, so could be at the beginning stages,
What do you guys think,
Cant be condensation now, Drove this car hot for an hour,
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From: Atlanta Metro
2008 clk550 - Navigator - Frontier
Unless you primarily just use the car to drive 2-3 miles to the grocery store, I personally (and I am not technical with cars) don't believe the condensation possibility. If you have owned the car for a couple years and drive normally, trips averaging more than 10 miles and near the speed limit, you shouldn't be getting that discoloration. IMO
My daughter kept her MY99 Honda Accord for years after she got her minivan. She drove the Accord maybe once every 3-4 months for less than 15 miles. When I was getting it cleaned up and serviced to give away to another family member, the gas cap was full of mold looking crud but all the fluids (even the brake fluid) "looked" normal. I had all the fluids changed.
I would just replace the oil cooler gaskets if you are comfortable doing it yourself, or have it done by someone who is engaged to fit the problem of coloration. That way, if it is not the gaskets, you can perhaps get a break on the labor for the next thing to do.
Or, as someone else inferred, it may run just fine the way it is for a very long time.... maybe.
My daughter kept her MY99 Honda Accord for years after she got her minivan. She drove the Accord maybe once every 3-4 months for less than 15 miles. When I was getting it cleaned up and serviced to give away to another family member, the gas cap was full of mold looking crud but all the fluids (even the brake fluid) "looked" normal. I had all the fluids changed.
I would just replace the oil cooler gaskets if you are comfortable doing it yourself, or have it done by someone who is engaged to fit the problem of coloration. That way, if it is not the gaskets, you can perhaps get a break on the labor for the next thing to do.
Or, as someone else inferred, it may run just fine the way it is for a very long time.... maybe.
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From: Johannesburg, South Africa
2004 CLK 320 Coupé
So again, just been to the garage down the road from our office to fill up on petrol, 15min max to go and come back, checked the cap and its completely clean, just normal oil, no mixing,
I don't know anymore...
Thanks for all the responses thus far gentlemen, really appreciate it.
I don't know anymore...
Thanks for all the responses thus far gentlemen, really appreciate it.
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From: Austin, TX
2006 E55, 2012 GLK350 & 1992 190e sportline
I would give it about a month. Don't even touch the oil cap anymore. It is not a good indicator. Keep checking your coolant level and do an oil change at the end of the 30 days. If you end up with chocolate milk or your coolant level has dropped you have a problem. Otherwise happy motoring.
