My friend has a 1996 960 with 340,000 km. The head was rebuilt 4 months ago. His son took the car on vacation and had the oil changed just before leaving with 10W-30. He drove 200 miles and parked the car for a week. His son checked the , thought it was low 2 liters - it wasn't- he just misread the dipstick, and overfilled it by 2 liters. He drove the car for several miles and noticed smoking from under he hood and warning lights were going off and on on the dash. He had it towed to a garage where they cleaned the flame trap, replaced a vacuum line? which was off and changed the oil to 15W-40. Car started fine, drove for 10 minutes but soon after getting to highway speed, he notices warning lights and smoke from under the hood. Car sat for 1 hour and started fine. Drove the car back to the garage and noticed a clicking sound, described as "slightly louder than a valve".

Car is still 200 miles from home and will be towed back in a few days. Does anyone have any thoughts as to what this overfilling would cause? Thanks for your thoughts.

Too much oil in the crankcase can build up excessive blowby pressure in the engine. This can push out the diptstick of even cause a leak in the hoses to the flame trap. I would check all the hoses to make sure they are attached tightly. I would also check the engine oil level again to verify.

15W40 seems awfully heavy weight for this engine. Not the 40 but the 15. I use 5W40 synthetic in ours and they run quiet but I would certainly not go any heavier than that. Especially not in a dino oil. Volvo recommends 10W30 here. Did he open the hood to see where the smoke and noise was coming from? The smoke could be coming from the dipstick tube, loose filler cap, loose/blown off oil trap hose.

The tapping sound 'could' be a lifter that has collapsed. Does it idle smoothly?

Still noodling.

DEWFPO
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1998 S90 077,400 and 1995 964 154,100

I don't know if it idles smoothly but he didn't say anything about it so I'm assuming that it does. I think they added heavier oil to see if it affected the smoking but it won't be driven much as the car will be towed back home. I know that he uses the synthetic that you do normally.

Thanks for your helpful comments.