Leaking CIS popoff valve
 

OK, I just got a CIS popoff valve ready to go into my car. I opened it up from its bag, and before drilling or anything I put it up to my mouth and tried to suck some air through it (don't try to visaulize this). Anyway, air flowed through pretty freely. It looks like at the hinge end, the lid doesn't seat fully against the O ring. Just by a little, but that's all it takes to leak.

I could proababy pull the O-ring out a bit and make a better seal, but suspect it would go away after a while. Does this sound like a deffective part, or normal? Is a little leaking OK? Would a gob of silicone grease on the O-ring seal this adequately?

Thoughts before I return this to our host?

Sound defective from what you tell us.

I just spent $50 on one, I sure hope mine doesn't have that problem. Now I got to go home & suck on it to find out. It would be nice to know before I get everything torn apart, I'm going to replace all my vacuum lines, injector lines, rubber boots, & gaskets while I have everything apart. Where did you get the valve?

Silicone grease should do it. Wipe and re-grease periodically is a good idea. Is the valve spring shot? If it has enough pressure, just grease it. The vacuum on the valve should hold it tight. I can't pull mine oipen when the motor is running, but it's easy with motor off.

I have heard several very negative posts on pop off valve failure. My "buying a used 911" book says they are not needed and are trouble. I understand the theory, but they sound like a bandage for improper tune, or worse, a fix for a non existent problem. Are they really reliable? Are the new airboxes less suceptable to pop back damage as they were earlier? Is this a MUST have or not? I bow humbly at the alter of your experience.

Bruce, I've got the manifolded cold start injection of the later CIS cars, and I believe my CIS is pretty well adjusted, I still get pops! Get one..It's cheap insurance. No matter how well you think your CIS is adjusted the valve is a good safety.

My spring seems good. The valve seems like it's the way it's "supposed" to be, just that it needs to be very precise to get a total seal. I would expect tolerances to be pretty good given that it's a $50 piece of plastic. It's probably curable with slight O ring adjustment and some silicone grease, but struck me as odd for the quality I expected.

Pschrup - check your valve and let me know if it does the same thing.

where I live, when the seasons change the temperature variations from day to day can be drastic.

one morinig it'll be 60 degrees and the next it could be 30 degrees. Thats when I get a few pops at start up. It's those days I'm glad I have a pop off valve.

I think a picture of you manually 'flow testing' your new pop off valve is needed for us to really see what is going on :D

ditto