I seem to have a problem with PCV valves hissing. I installed a Fram on my 71 Duster 225 and it hisses. I then installed a premium CarQuest valve (Wells I think) and it hisses. The grommet and hose are both new and are not leaking. It's kinda annoying...and not normal I would imagine. Any ideas?

 

When I bought my truck, '72 340 cid the PCV valve rattled. Like open/closed very fast. I replaced it and it stopped the rattle. But I noticed in the process that it rattled more when the engine was cold and less as it warmed up.

I did not have a vacuum gauge at the time but my guess is that when the engine was cold there was less vacuum to open the valve.

I also noticed a vibration along with the rattle, do you feel any kind of vibration?

However mine never sounded like a hiss that you describe.

Not much help I know, but hope you get it figured out.

Joe.

 

The noise is there when it is cold and hot and it doesn't rattle any. What are the chances of two bad valves?

 

My knee jerk answer would be more likely the wrong valves rather than two bad ones. Also I can't get passed the "hiss" as that sounds like a leak, but I know you said you checked??? I guess I'm of no help.

Joe.

 

PCV is supposed to rattle. Hissing is a vacuum leak.

 

I put a clamp on the hose and moved the valve around in the grommet to see if the hiss would go away and it did not...Ill have to investigate further