2012 Chevy Sonic 1.8 - "Chocolate Milkshake" in Coolant Reservoir

[Number_35]

This is my friend's 2012 Chevy Sonic 1.8 once again.

One of the heater hoses blew last April. I replaced it and a bunch of other hoses, and the thermostat housing. At that time there was a lot of yellowish "mayonnaise" in the cooling system, which I attributed to my friend having added generic antifreeze to the system.

The car subsequently had a leak from a brittle plastic pipe (coolant to throttle body), and before I replaced it, my friend topped up the system with quite a bit of water, which diluted the coolant a lot.

He brought the car over yesterday so we could add coolant before winter. (In the nick of time, as it was snowing today.)

Anyway, I was dismayed to find lots of brown foam in the coolant reservoir. I said "chocolate milkshake" in the title, and that's a pretty good visual description.

I feared a blown head gasket, but was glad that the leakage (oil into coolant) appeared to be one-way only. Coolant into oil could take out the engine quickly, but the oil looked good.

Poked around the 'net a bit, and discovered that there's an oil cooler, which the oil filter housing is mounted on, which tends to fail, causing exactly this symptom.

@14Accent, you've offered good advice on the Sonic in the past. Do you think the most likely cause is the oil cooler? Thank you!

 

[thomasflaherty]

check you trans fluid to make sure your trans cooler failed an mixed with the anti freeze remember the trans cooler is part of the radiator if it a auto trans

 

[Number_35]

check you trans fluid to make sure your trans cooler failed an mixed with the anti freeze remember the trans cooler is part of the radiator if it a auto trans

Thanks, good thought. I'm pretty sure this is motor oil, though. I've seen ATF in coolant, and it's definitely reddish.

 

[dishdude]

Hot many times was it overheated?

 

[ka9mnx]

Oil cooler is leaking oil to the water coolant .

 

[Number_35]

Hot many times was it overheated?

Just the once, as far as I know. That was when the heater hose burst in April.

The driver pulled over as soon as the temperature light came on (typically 250°F). Unfortunately, there's no temperature gauge.

Edit: Hoping it's not the head gasket!

 

[Number_35]

Oil cooler is leaking oil to the water coolant .

That's my hope. Much easier to repair than a head gasket.

 

[14Accent]

This is my friend's 2012 Chevy Sonic 1.8 once again.

One of the heater hoses blew last April. I replaced it and a bunch of other hoses, and the thermostat housing. At that time there was a lot of yellowish "mayonnaise" in the cooling system, which I attributed to my friend having added generic antifreeze to the system.

The car subsequently had a leak from a brittle plastic pipe (coolant to throttle body), and before I replaced it, my friend topped up the system with quite a bit of water, which diluted the coolant a lot.

He brought the car over yesterday so we could add coolant before winter. (In the nick of time, as it was snowing today.)

Anyway, I was dismayed to find lots of brown foam in the coolant reservoir. I said "chocolate milkshake" in the title, and that's a pretty good visual description.

I feared a blown head gasket, but was glad that the leakage (oil into coolant) appeared to be one-way only. Coolant into oil could take out the engine quickly, but the oil looked good.

Poked around the 'net a bit, and discovered that there's an oil cooler, which the oil filter housing is mounted on, which tends to fail, causing exactly this symptom.

@14Accent, you've offered good advice on the Sonic in the past. Do you think the most likely cause is the oil cooler? Thank you!

I'd go ahead and replace the entire assembly. I haven't replaced one due to oil intrusion into the coolant, but I have had to replace the plastic coolant lines and run to and from the assembly. Make sure and replace EVERYTHING while you're in there: every single plastic/rubber/one use item you can get your hands on.

A quick peek at the parts diagram shows no less than 5 separate items you're going to need.

 

[chrismo]

I worked on these awful things in one of my previous jobs, in Australia it was called the Holden Barina. In 99% of cases it was only the oil cooler seals which failed causing coolant and oil to mix, not the exchanger itself. Unfortunately there's a good chance most of the rubber cooling system components are already compromised, however you could try a good cooling system flush and see how it goes.

 

[Number_35]

Update on the Sonic: My friend has parked it for the winter, and is using his van instead. (Usually the van gets parked for the winter.)

I'm willing to take on the repair next spring, hoping that I don't break any exhaust manifold bolts.

 

[supton]

Removing the battery for the winter?

 

[Hermann]

En el nombre del padre, del hijo y del Espíritu Santo, Amén.

Just a blessing for the Sonic

 

[The Critic]

Hot many times was it overheated?

I pronounce @Number_35 and Sonic, husband and wife.

 

[Number_35]

Removing the battery for the winter?

Likely not, but I'll mention to my friend.

 

[Number_35]

I pronounce @Number_35 and Sonic, husband and wife.

And just like a marriage, one must work at it ... or in the case of the Sonic, on it.

I think it would have been a better car to date if it had had more PM. At this point I'm mostly doing repairs.

 

[The Critic]

And just like a marriage, one must work at it ... or in the case of the Sonic, on it.

I strongly recommend walking away. Cars with a questionable history combined with an owner who is not willing to invest in the proper, thorough repair - are cars that one should not become involved with. They tend to become situations of "ever since you..."

I always test the situation by inspecting the entire vehicle and making a list of items needed to make the car up-to-date; if the owner balks or isn't interested, I won't help.

 

[Number_35]

I strongly recommend walking away. Cars with a questionable history combined with an owner who is not willing to invest in the proper, thorough repair - are cars that one should not become involved with. They tend to become situations of "ever since you..."

I always test the situation by inspecting the entire vehicle and making a list of items needed to make the car up-to-date; if the owner balks or isn't interested, I won't help.

He's a good friend with a hard life and not a lot of money. I'm glad to help where I can.

I do explain first how I'm not a professional mechanic, and although I'll always do my best, I might make mistakes. So far, so good.

 

[The Critic]

He's a good friend with a hard life and not a lot of money. I'm glad to help where I can.

I do explain first how I'm not a professional mechanic, and although I'll always do my best, I might make mistakes. So far, so good.

Unfortunately, those also tend to be the most vulnerable situations, so proceed at your own risk.