1981sc pop off valve fixable?
 

1981 911sc-Long post alert and a Newbie to the CIS system.

Never had an issue with backfire up until yesterday. After car sitting for only 2days, On cold start I got 1 immediate loud backfire and then the engine would only crank and not turn over. I immediately inspected the air box and confirmed the pop-up valve has “popped off.” Another words instead of the flap just opening there was enough force to break the adhesive securing the valve to the airbox and it was just sitting inside under the filter. I never had an issue with backfire or my air box/valve for the 5 years I’ve owned this car until now and no visible cracks upon inspection of the airbox.

My question is can I clean the the area around the hole for the valve and reinstall it? since there’s no other cracks in the airbox or valve itself? Or should I look into a whole new airbox/maintenance that comes with that project. The 2” hole for the valve is perfectly intact just the adhesive gave way allowing it to pop off from the airbox as mentioned before.

Thanks for anyone’s help with this.

Clean out the old glue and redo. Happens a lot.

Definitely reuse [emoji1303]

Some of them are defective......
 

Test the old or new pop-off valve before installing it. You don’t want to know it is not sealing well after you installed it to the airbox. A simple vacuum test will show how a good working POV holds vacuum. If it can not hold vacuum, it is leaking.

Tony

And, use JB weld.

i grinded down the ribs so the valve can sit down in and get a better seal. also helps with clearance to the air filter. Also make sure you glue it in backwards so it doesnt foul on the filter

Follow this sage advise.......
 

+1. The contact surface between POV and airbox will increase more than 300%.

Tony

Forget the JB Weld and get the proper plastic epoxy adhesive at a auto parts jobber. Remove the ribs so you get more glue area and a better seal.
Like others said, do a vacuum check after install. I also added a bit of silicone grease to the O ring to promote the seal when in operation.
Jeff

Use coarse sand paper to prepare the surface so the epoxy has something to adhere to - clean with acetone the area, as residues of oil will lead to bad adhesion, and finally, be careful with the orientation of the pop off valve, it should open without interference of the paper air filter