QuestionQUESTION: Dear Mark, I recently purchased a 1996 volvo 850 turbo. I am really happy with it, but it's got a few problems. I was wondering if you could help me out with them.
My break (stop) lights are not working, and it seems to be the trigger under the break (the stop light switch). I just ordered one from the internet, and I was wondering if you think I should change the switch myself, or have a mechanic do it. (Is it hard? and if it is do do you think you can explain how to do it?)
#2. My car has a small oil leak, and when I drive, sometimes there is mild smoke and it smells like some burning smell (maybe it's the oil dripping). I think the leak is coming from the engine oil cap. Is that common? Also I was wondering if you think the smoke is coming from the oil leak as opposed to some problem in the engine.
Thank you for your time and expertise.
-Yitz
ANSWER: Yitz, the switch is pretty easy. Just pull the bottom dash panel and follow the pedal up to the switch bracket.
I'm pretty certain the smell and smoke is from the leaking oil burning off on the exhaust system. If it's coming from the oil cap, you probably have a plugged flame trap that needs cleaning. It allows excess crankcase pressure to be sucked through the intake system and be reburned. HTH
Mark
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QUESTION: Thank you Mark! Where is the flame trap, and how do I clean it? (and what is crankcase pressure?).
All the best, Yitz
Answer As combustion occurs in the cylinders, some pressure escapes past the piston rings and into the crankcase. This pressure builds up over time. Since it is basically exhaust gasses and oil, it is no longer just "vented to atmosphere like the good ol' days. It is now recaptured by the intake system and burned. It goes through a filtering system to remove the oil and let it drain back into the crankcase. This keeps the possibility of a flash back occuring in the intake system. Thus the phrase flametrap. This filter can get plugged eith crap over time and the pressure is not drawn off of the crankcase.
On the 2 and 7 series. It was a small plastic canister about the size of a large cigar butt in the vacuum line that ran to a nipple on the block. There was a metal coil (The trap) that gets plugged. You could replace it or clean it with a solvent.
On the 8 series, I think it's a small plastic tank with a filtering agent in it. I forget the location, but it will be very near the side of the motor and have a vacuum line connected to it. Sorry I can not remember better.
Mark
