850 T5 - Brown coolant Topic is solved

madsking · Post by **madsking** » 11 Aug 2025, 06:06

Good afternoon.

Coolant has gone from pink to brown color lately. It can be head gasket broken or somewhere else oil is mixed into the coolant but there is no trace of bad smell, coolant smells normal and doesn't seem thicker than normal. Also coolant level is stable.

Any experience from you of a possible reason not being a dead head gasket specifically for this engine perhaps? Corrosion somewhere?

Thank you in advance

Best regards
Mads (Denmark)

Post by **scot850** » 11 Aug 2025, 08:47

It is possibly oil leaking into the coolant. Other than the head gasket, does your car (automatic or manual?) have an oil cooler for the engine with pipes that run to the RHS of the radiator? The engine cooler on turbos normally have this and they can fail inside the radiator allowing engine oil and coolant to mix. The other place could be the turbo coolant leaking into the oil.

Neil.

Post by **MoVolvos** » 11 Aug 2025, 09:17

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If the expansion tank fill hole is larger than the block tester use a large funnel with the tip cut off so it doesn't draw up coolant into the tester fluid. The kit could be borrowed from Advance Auto and you just pay for the fluid.

BT-500 Head Gasket Combustion Leak Test Kit - Made in USA
https://www.amazon.com/Block-Tester-BT- ... 245&sr=8-3
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Post by **abscate** » 11 Aug 2025, 11:14

Both the turbo and radiator cooler failure scenarios are rare. I think a compression test is immediately in order, as a bad result there is definitive. A good result there is not as definitive, but then the gas test guides you.

madsking · Post by **madsking** » 11 Aug 2025, 12:26

Thanks all for very very good answers.
I did not consider the radiator at all, but for sure there is a possibility that the radiator has a breach inside, even though it's rare. Oil pipes are going in there (manual transmission btw). Don't know how to identify that cooler is defective other than replacing it, any suggestions?
However I might start with a thorough gasket test then, before focusing on the radiator. Not to forget the turbo

I have broken one before

Post by **abscate** » 11 Aug 2025, 16:00

We are still in the warm weather in northern climate. Run out the coolant and replace with water and see if it gets milky from oil.

Coolant needs 3 years/ 30000 mile replacement on modern engines. Maybe you did get a slug of rust being released somwhere