Hello All:

1967 Volvo 122S wagon. I have been hearing a rattle or buzz from the engine compartment, only under very particular RPMs and other running conditions. I have isolated the noise to coming from inside the oil trap. Any clues?

Cheers,

Jeff Pucillo

Jeff;

PCV valves (located just above the oil trap) like to rattle when the idle RPMs equal the mechanical resonance of the valves' shuttle...I wouldn't worry about it too much unless it really bothers you...or you could clean the valve insides with carb cleaner...the mass change alone might change its resonance point enough...or just adjust the idle Rs a bit...it's typically a very tight match which causes the rattle...

Cheers

Hello Ron:

Okay, thanks for the response, but help me out here. I looked through the shop manual and I cannot find a mention of the PCV valves. What are they, where are they, what does PCV stand for? Not the same as PCV tubing used in plumbing? The valves' "shuttle" - sorry to sound ignorant, but huh?

Cheers,

Jeff Pucillo

PVC = poly vinyl chloride (plastic plumbing pipes)
PCV = positive crankcase ventilation

Jeff;

"Shuttle" is the movable dingus* within the valve which opens by lifting off a seat under vacuum, or closes by spring pressure.

See also: http://www.intelab.com/swem/pcv_diagrams.htm

* that's called: explaining one unknown with another!

Cheers

Hello All:

Thanks for the very informative posts. I learn something new about these beasts every day, like it or not.

Cheers,

Jeff Pucillo