2001 s60 non-turbo, weird noise caused by suction on oil cap

lukevolvo · Post by **lukevolvo** » 05 Aug 2007, 19:59

I posted this before claiming it wasn't a vacuum leak, it appears to be a clog. The car has 100K miles. Recently had timing belt and water pump replaced (unrelated preventative maintenance).
Had a weird noise at idle, goes away while driving. Discovered that noise goes away when you loosen oil cap. This is tough to do because of the suction force put on it. Checked the PCV system, these cars don't have PCV valves. Found the bottom inlet to the cannister completely clogged with carbon deposits. Cleaned it out. Replaced the short hoses going to and from the cannister. Replaced the gasket on the oil cap with my fingers crossed. Car runs significantly better but noise and suction are still there.
I have checked the oxygen sensors and mass air flow sensor, all appear to be fine. Car spit out a check engine light for lean fuel mixture (OBD P0171) lean on bank one. After cleaning the clog the engine light went away.
Any suggestions or ideas?

Post by **MadeInJapan** » 06 Aug 2007, 06:47

If the PCV is working correctly, there should be suction on the oil cap. So....don't know about your noise. How's the car running otherwise?

lukevolvo · Post by **lukevolvo** » 08 Aug 2007, 17:47

It turns out that the oil seperator, black box under the intake manifold, was not working properly. I attempted to clean it out with carb cleaner and air but the car failed again within a day or so. I read somewhere that most people didn' have luck cleaning it. I bought a new one from the dealer for $45 replaced it and the car is running fine. It has been driven roughly 200 miles in the past three days with no problems. There is a slight vacuum on the oil cap and dip stick but with the old oil seperator it was strong enough that you could barely remove the oil cap by hand.

Weird idle noise was clogged oil seperator.

Thanks for all the help and input.

Post by **MadeInJapan** » 08 Aug 2007, 18:34

Glad it's all working now...very strange indeed. Usually if the PCV system (including the oil separator) is clogged there is positive pressure- not the other way around....so, it's always good to learn a new thing or two.