I've had a perplexing problem with a customer's car. She had the oil changed, and when she checked it, the oil level was too high. I figured the oil change place put too much in, so I drained it and corrected the level. She called me today, and said the level is too high again. What could be happening? PCV system is in good shape. Car is an S70 GLT.

 

Does it have the proper dipstick in it?
How much did you put back in?

 

Yes, the car has the proper dipstick. When I corrected the oil level, all I did, since it was fresh oil anyways, was drain off a few quarts, then I topped it off to where it was exactly full. The oil level seems to go up over the course of a couple days of sitting- I can check the oil 20 minutes after shutdown, and it will be fine, but if the car sits for a couple days and you go out and check it, it is about 1- 1.5 quarts too much. There's no sign of sludge build- up in the engine that could be causing the oil to sit up in the cylinder head. My thought on this one is: is there some kind of check valve in the oil thermostat that prevents the cooler from draining back? And if so, could that be leaking, and allowing the cooler to drain into the engine over time?

 

I do not think there is a valve like that.
Do you know if the head had been done on the car?
Something is holding oil somewhere and draining over time. I doubt it is the cooler though.
Also what year is it?

 

Okay... confession time I was in a hurry when I posted this... wrote the whole message, then realized I was in the S70 forum. It's actually a '95 850 Turbo... the self- same one I just replaced the head on with a used one. Car runs great, but has this oil issue. So... what in the head could be causing it to "hide" oil?

 

Not to sure I wonder if the lower end has sludge.
You might want to do a total drain and refill. Try putting 5.5 quarts instead of 6 in there and see what happens.