Oil in coolant / No oil in crankcase

#1

I’ve got oil in my coolant, which happened when my water pump seal blew out while I was running the car hard, ran out of water, overheated, started blowing blue smoke out the tailpipe and making a sound like a hail storm under my hood.

When I pulled the water pump, I noticed a fairly decent amount of oil in the coolant. But surprisingly (to me) there was no coolant in the crankcase.

Has this ever happened to anyone? Does anyone know how oil could migrate into the water passages? Does this sound like a bad head gasket or worse? On a positive note, after the engine cooled off, I started it, and it ran fine (as in no horrible noises from the valve train). I had it towed home and was able to drive it into my garage.

I don’t want to tear the engine apart all willy nilly only to find out it was unnecessary, so any help would be awesome.

I’ve got a '90 325i. Stock motor & drivetrain.

Thanks!

#2

barrstev wrote:

[quote]I’ve got oil in my coolant, which happened when my water pump seal blew out while I was running the car hard, ran out of water, overheated, started blowing blue smoke out the tailpipe and making a sound like a hail storm under my hood.

When I pulled the water pump, I noticed a fairly decent amount of oil in the coolant. But surprisingly (to me) there was no coolant in the crankcase.

Has this ever happened to anyone? Does anyone know how oil could migrate into the water passages? Does this sound like a bad head gasket or worse? On a positive note, after the engine cooled off, I started it, and it ran fine (as in no horrible noises from the valve train). I had it towed home and was able to drive it into my garage.

I don’t want to tear the engine apart all willy nilly only to find out it was unnecessary, so any help would be awesome.

I’ve got a '90 325i. Stock motor & drivetrain.

Thanks![/quote]

Others will chime in on this but I’m having problems imagining how a blown waterpump seal can put oil into the water jacket. Oil in the water is classic headgasket. The oil is under far more pressure then the coolant, so oil will tend to migrate to the coolant if a blown HG allows it.

The noisy motor that later quieted down is worrisome. I’ve got an overheated motor to pull apart and figure out myself, but a guess would be that the first thing to get damaged in an overheated motor is the headgasket, and the head & pistons because they are aluminum. But if your motor seemed to run ok, then it must be ok. Might be worth doing a compression and/or leakdown test tho.

And watch the oil and water quality like a hawk for a while.

#3

Thanks for the info. That was my guess as well, but I don’t know a lot about these motors since I’m just getting into 'em. Next question, I’m running 60psi oil pressure at high RPM. Is this a normal operating pressure?

#4

Are you sure there is no water in the crankcase? Drain some oil into a container and let it sit to see if it separates.

Does sound like a headgasket.

#5

Oil in the coolant is just one of the possible manifestations of a blown head gasket.

#6

barrstev wrote:

That’s fine for “warm” 20W50, at least for my motor and most xW50’s that I’ve tried. Cold oil pressures will be higher, maybe 65-70psi depending on your oil checkvalve. Hot lighter weight oils will result in lower pressures. Here’s some ballparks:
Hot xW50 55psi
Hot xW40 38psi
Hot xW30 30psi

These are just #'s from my experiments tho, so other folks will see different results. The biggest variable is the condition of your bearings, and the other is that all oils are different. Brand X 10W40 can be pretty different from Brand Y 10W40, and this year’s Brand X isn’t always the same as last year’s Brand X.

#7

Thanks a lot. That answers all of my questions. Now for the fun part…