[Bubble]

I have a 2017 Cadillac ATS coupe with an automatic transmission. I bought the car at 44k miles and it now has 48k and I haven’t had anything done to it. The car overheated and I immediately pulled over. I found brown sludge bursting from the coolant tank (first picture below). My first thought was a blown head gasket but the engine oil seems fine (second picture below). I’ve seen online that it could be transmission fluid contaminating it or an engine oil cooler failure. Any way I can determine what caused this? Also, if it was either of those two, how much should I expect to be charged for this repair? I’m just trying to get as much information as possible on this to make sure I don’t get scammed by a mechanic since I don’t really have a trusted one yet.

 

[Byrdman]

I'm not an expert on your model car, but my first guess is someone put sealant tabs of some kind in the cooling system. If so, keep an eye on temp. If that's what happened look for the cause.

 

[ELDORADO2K]

keep an eye on temp

Captain Obvious… lol.

 

[rmfats]

NEVER use any kind of additives in coolant, oil, or the transmission! Get it repaired instead. The only exception I make is using a bottle of Water Wetter in every car I have had, in the radiator.

 

[ELDORADO2K]

NEVER use any kind of additives in coolant, oil, or the transmission! Get it repaired instead. The only exception I make is using a bottle of Water Wetter in every car I have had, in the radiator.

He didn’t add anything. He bought the car only 4,000 miles ago as is.

 

[Submariner409]

Water Wetter is a surfactant - its equivalent is already in every coolant (antifreeze) on the market. You don't need to add more - and engine temperature is controlled by the thermostat, not a magic potion.

Surfactants and anti-foams (as well as system pressure) are used to improve heat transfer from engine metal to coolant.

The first picture looks suspiciously like engine oil mixed with coolant - is the engine losing oil - without obvious drips on the floor?

 

[rsingl]

I agree with Sub that this looks exactly like what happens when engine oil and coolant mix.

I believe the 2.0T likely uses a water cooled center bearing for its turbo and that would be a potential mix point with that engine, otherwise a stacked plate oil to coolant heat exchanger is used for many trim/powertrain variants in the ATS lineup and a failure there could be the contamination point.

Rodger

 

[Bubble]

The first picture looks suspiciously like engine oil mixed with coolant - is the engine losing oil - without obvious drips on the floor?

I think so. There is no obvious drips to the floor and the engine oil is low. Granted I only checked it when the car wasn't running and I was afraid to turn the engine on with no coolant to check.

 

[Bubble]

I agree with Sub that this looks exactly like what happens when engine oil and coolant mix.

I believe the 2.0T likely uses a water cooled center bearing for its turbo and that would be a potential mix point with that engine, otherwise a stacked plate oil to coolant heat exchanger is used for many trim/powertrain variants in the ATS lineup and a failure there could be the contamination point.

Rodger

Awesome, thank you for the suggestions! Any idea how much these repairs could cost?

 

[rmfats]

Water Wetter is a surfactant - its equivalent is already in every coolant (antifreeze) on the market. You don't need to add more - and engine temperature is controlled by the thermostat, not a magic potion.

Surfactants and anti-foams (as well as system pressure) are used to improve heat transfer from engine metal to coolant.

The first picture looks suspiciously like engine oil mixed with coolant - is the engine losing oil - without obvious drips on the floor?

Where I live in the Southwest the ambient temperatures can reach 120. Extra surfactant can help with needed heat transfer under these conditions to help prevent overheating.
I don't use magic potions (or the term, either).

 

[rsingl]

Awesome, thank you for the suggestions! Any idea how much these repairs could cost?

Bubble,
The cost could be all over the board from the simple (someone foolishly dumped oil in the coolant tank, rare but I have heard of this twice) to very expensive (internal block damage). In general, I think you are better off with a third party garage if there is a trusted one in your area because the costs will generally be far less and neither the 2.0T nor 3.6 engines used in the ATS are anything exotic that requires a dealer tech.

Rodger

 

[Mad*Max]

Is there a coolant leak anywhere, the orange Dexcool stuff can form sludge when exposed to air (just one possibility for you to consider speaking from personal experience)?

 

[ELDORADO2K]

Is there a coolant leak anywhere, the orange Dexcool stuff can form sludge when exposed to air (just one possibility for you to consider speaking from personal experience)?

When the sludge formed, were you able to notice it from the surge tank? Or where did you 1st see it?

 

[Mad*Max]

When the sludge formed, were you able to notice it from the surge tank? Or where did you 1st see it?

I noticed it in the surge tank only, it was a different vehicle. Once I fixed the leak and cleaned out the tank, refilled the coolant, all was good thereafter.

 

[ELDORADO2K]

I noticed it in the surge tank only, it was a different vehicle. Once I fixed the leak and cleaned out the tank, refilled the coolant, all was good thereafter.

Ok, thanks for the reply.

 

[Cadillac Customer Service]

I have a 2017 Cadillac ATS coupe with an automatic transmission. I bought the car at 44k miles and it now has 48k and I haven’t had anything done to it. The car overheated and I immediately pulled over. I found brown sludge bursting from the coolant tank (first picture below). My first thought was a blown head gasket but the engine oil seems fine (second picture below). I’ve seen online that it could be transmission fluid contaminating it or an engine oil cooler failure. Any way I can determine what caused this? Also, if it was either of those two, how much should I expect to be charged for this repair? I’m just trying to get as much information as possible on this to make sure I don’t get scammed by a mechanic since I don’t really have a trusted one yet. View attachment 629888
View attachment 629887

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[ajg3483]

Just had this happen to my 2014 ATS 2.0T, transmission fluid mixed with coolant, creating that sludge. Radiator was replaced, and transmission flushed about 4 times. Running smooth, no transmission hesitation since the repair, only about 2 weeks so far.