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Oil in the coolant overflow tank

1996 Subaru Legacy Outback 2.5 L automatic.Why would I be getting oil in my coolant overflow tank? I had the coolant system flushed and thermostat replaced last year after getting close to overheating. I do regular maintenance.

The news is bad and badder.

You could have a bad cylinder head gasket. Less bad would be a leak in your radiator where the automatic transmission cooler is also connected. I don’t know for sure that your Subaru radiator has a compartment for oil or transmission cooler as well as the expected engine coolant.

I would strongly suspect a breached head gasket, simply because this model is known for that weakness.

I would suggest having your mechanic perform a compression test a.s.a.p. in order to determine if you do indeed have a bad head gasket or two. Don’t delay, as it is also possible for coolant to be migrating into the crankcase oil. Since coolant is not a lubricant, this can spell a quick demise for the engine.

Our decision now is to choose what kind of newer engine we want to put into this car. Everything else on the car is in good shape and spending the money on an engine swap is cheaper than another used car with unknown problems and a new car is out of the question.

So, are the Japanese used engines worth the time or should we try to find a more expensive rebuilt engine?

It’s a crapshoot. I’ve had good luck with engines from Nippon Motors. We got motors with around 30k miles on them and they usually had a DOA guarantee. That was years ago, though. Dunno if they’re still in business even.

The trouble is that, just like a used car, you’re getting an engine that someone else used and maintained (or didn’t maintain). You have no idea how it was treated or how it was run.

Expect to replace anything that’s bolted on to the motor, if it’s even there at all. Distributor, alternator, headers, etc. The only thing you’re sure to get is the head, the block, and anything that’s supposed to be on the inside of those parts. For that reason, if you got a used motor you’d want to get either the same one your car came with, or one that directly bolts on to your car without having to swap anything.

The same happening to me a few days ago. Just saw oil on my coolant overflow tank and confused what would be the cause of this. I’ll follow your advice to conduct a compression test. I just hope no bigger problems will occur.