Oil cooler or head gasket?

[befarrer]

I have been noticing over the last 6 months a milky film building up in my coolant bottle. Today I checked, and can see black oil floating on top of the coolant. I have no coolant in my oil, I have been sampling it for the last year, and it has always come back negative for glycol. My oil has to be leaking from a pressured oil source into the coolant, my guess is the oil cooler in the rad leaking. But has anybody had the head gasket leak from the head oil pressure gallery into the coolant? I have lost zero coolant in 2 years.

[MoVolvos]

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The coolers seem cheap enough but not sure if prices are the same in Canada.

https://www.partsgeek.com/catalog/1998/ ... ooler.html

Before replacing however, go to the big box stores and get yourself a coupling and bypass the cooler. Weather is cool so no harm to the engine as the car will warm up quicker which is not a bad thing. Clean the coolant reservoir and see if the oil issues stops or dramatically lessons as there maybe some residue floating around.

https://www.homedepot.com/p/1-in-Brass- ... 92#overlay

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Brass Barbed Coupling.png (452.39 KiB) Viewed 2769 times

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[abscate]

Parts geek has that wrong..that’s the turbo 1999- biscuit oil cooler.

Trying to use some logic and maths here…coolant pressure is 14 psi roughly, oil pressure 60 psi at coldstart, then roughly 10 psi per 1000 rpm.

Oil cooler
Head gasket
Turbo

Are the places where oil/ coolant are in proximity

[kallekula]

I had an internally leaking oil cooler on an XC90 once. The oil looked like thick brown milk chocolate or something. Absolutely awful. Funny thing with that car was that the head was also warped

[befarrer]

Yeah, it has to leak where the oil pressure is greater than the coolant pressure, I'm running a lower pressure coolant pressure cap too. My oil cooler and transmission cooler are both in the Radiator. I'm planning on pulling the engine to refresh the seals and re ring the engine this year. I wonder if I can get by just bypassing the engine oil cooler for a month to see if the oil stops.

[befarrer]

Parts geek has that wrong..that’s the turbo 1999- biscuit oil cooler.

Trying to use some logic and maths here…coolant pressure is 14 psi roughly, oil pressure 60 psi at coldstart, then roughly 10 psi per 1000 rpm.

Oil cooler
Head gasket
Turbo

Are the places where oil/ coolant are in proximity

For the head gasket, there is usually only one oil pressure supply port through the gasket to the head, narrowing down the failure area to one spot, and usually these start to leak externally instead of into a coolant port, but I'm not familiar with the Volvo gasket.

[MoVolvos]

my guess is the oil cooler in the rad leaking.

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Do you have the turbo or NA? Couldn't find info on oil cooler on IPD or FCP for NA. Can you confirm the oil cooler is in the rad or were you thinking trans fluid from rad leaking? Regardless, if you can bypass whether by rubber hose or barb coupling it will help with the troubleshooting.


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[befarrer]

It's in the rad, I have a 98 AWD LPT. The trans cooler is on the left side, oil cooler on the right side of the rad.

[erikv11]

Leaking oil cooler (in the rad) is fairly common for an old radiator. But yes all of the unidirectional leaks are possible for the head gasket, it just depends where and how the gasket is breached. Mixing in the turbo is most uncommon.

oil cooler > head gasket > turbo (in terms of probability)

[befarrer]

Now that I think about it, I am sure it's my oil cooler. When I bought the car in 2019, the oil cooler hose had a pin hole in it. I took the hoses to a hydraulic shop to repair, and the replacement hose was quite stiff, and was difficult to install. I bet the stress on the rad from the hoses lead to a hairline crack.