Pop-off valve vacuum leak

[Jerome74911S]

By applying air pressure to the intake system, I have discovered a number of vacuum leaks around the pop-off valve by using squirted soap water, which made bubbles.

The issue lies with the epoxy (?) that was used to install the valve by a PO. It appears to be peeling off, partly, and has flaws in it while the valve remains solidly attached.

There are plenty threads on here that discuss installation of a pop-off valve, but I have not seen one about getting a problematic valve back out of the air box.

How should I go about sealing up the leaks? The air box screws seen in the first photo are tight, but they leak, too.




There are also leaks on the backside of the valve. I can't get my fingers in there. Any ideas? This is before cleaning it up.

[Howard M]

You really have to get that sucker out of there and clean up both the enclosure and valve surfaces. I'd try an exacto knife. When it's out, roughen up both surfaces and use a high quality, long cure epoxy. Use enough so that there is a generous fillet of cement all around, confirmed with that dental mirror of yours.

[Jdub]

A rule of thumb for a blown airbox is the ability to put a fingernail under any screw head. That crack on the backside is also problematic. If you were to remove the entire airbox to fix this, I would instead replace it. If you elect to seal it, get a reasonable hi-temp sealer (others will pipe up with fave brand). And yes, you probably should remove all current sealant and determine the fit of the valve to airbox before sealing. But you might get lucky with a pinky finger swipe and proper sealing time.

I would be interested in knowing what the air filter looks like directly above your popoff valve - dented? Just want to confirm it IS opening.

[Jerome74911S]

Originally Posted by Jdub

I would be interested in knowing what the air filter looks like directly above your popoff valve - dented? Just want to confirm it IS opening.

It opens. I watched it do so when a massive air leak elsewhere (quickly resolved) made the engine pop like mad.

[Jerome74911S]

Originally Posted by Jdub

That crack on the backside is also problematic.

I just went out and checked. After cleaning, it appears to be the old epoxy peeling, not a crack in the air box. I need to do a more thorough cleaning, but examination with my 'dental mirror' suggests that an in situ repair might be possible. At least its worth a try. JB Weld?

[sailchef]

Originally Posted by Jerome74911S

By applying air pressure to the intake system, I have discovered a number of vacuum leaks around the pop-off valve by using squirted soap water, which made bubbles.

Could you explain this procedure a little more? I would like to try it. It just sounds like a very sensible way to find leaks. Where did you make the connection, how much air pressure etc.

Thanks

[Jerome74911S]

Pretty low tech. I have a not-too-powerful shop vac that converts to a leaf blower. I washed and cleaned everything, used a new filter, etc., then hooked the vacuum's hose to the 'exhaust' of the blower. I put the hose into the tail pipe and duct taped in place. ThenI taped over the throttle aperture and turned the thing on. I knew that the pressure was not great, due to the smallness of the blower.

Then I took a squirt bottle with soapy water in it and squirted here and there. What do you know, bubbles appeared, as described in my OP. Simple as that. Really, the pressure was small, and I got results.

[Paulporsche]

I'm probably stating the obvious here, but make sure there are no other leaks after the valve is repaired. There's a reason why it failed in the first place.

[Jdub]

The quick fix would be to take some bathroom-type caulking and using your finger or a tongue depresser/popsickle stick get the stuff in there and pushed into the cracks/air holes. On reflection, I am not sure a hi-temp substance is required here (others? am I wrong on this point?).

But the airbox screws are a concern. They should be locked down solid and provide no lift or play with the airbox at all. A stub phillips screwdriver may let you access and check tightness on all of them.

I would continue with your testing after applying and allowing proper drying and set up time. After all of this, a redo on your CO2 and idle speed may be in order.

EDIT: I'd also like to point out (without being mean) that your airbox looks really, really dirty. Surprised at the level of dirt on the popoff valve and the rest. This area is a holy ground, and should be absolutely immaculate. I HIGHLY recommend you totally clean the inside of the airbox, remove the rubber plenum between the throttle body and CIS and clean that item, plus the hose that routes from the oil tank upper takeoff (directly below the oil fill cap on the oil tube neck) to that plenum. Check to be sure a bit of wire mesh or similar "inhibiter" is in place at the oil tank end of that rubber tube - this prevents (badly) oil from directing itself into the plenum/CIS sensor plate/throttle body. On that point, you should be VERY careful never to overfill the oil. I keep mine exactly 1/3 up the stick, just below half. Clean the sensor plate (it can get heavy from buildup and act differently on mixture, etc.) as well, and replace that darn air filter they are cheap.

Finally, and totally over the top, mark a date with a Sharpie pen onto the air filter where the popoff valve dent is, then rotate the air filter so that the dent is now no longer over the valve. Next time it blows, mark again to track the blowup.

EDIT2: I mean, that airbox is super amazingly dirty. That pic shows the post-filtering chamber, and my gosh that stuff is headed right for your engine. Look at the dirt in the crevices, and around the spring and pivots of the valve. Sorry to be a jerk, but you could EAT off of the inside of my airbox it is so clean. Toothbrush, warm water, and get at that crud my friend. Then fire your air filter (hope this is not another K&N...) and get a fresh factory air filter in there.

[area man]

I had the same problem. I tried sealing it with JB weld while the airbox was still in the car, but it didn't work. Depends on where the leaks are, but I had tricky ones just next to the plastic 'fins'.

fwiw, my solution was to pull the airbox from the car, take it apart, reglue the whole thing with right glue, and seal the pop-off valve from the inside with a bead of glue (Plus extra JB weld on the outside for good measure). That worked. I did it with engine out, but i've also pulled the airbox out with engine in the car ('partial drop' - a few inches does it). on the whole, slightly easier, but still a bit of a PITA.

+1 paulporsche - figure out the cause of the backfires. if no other air leaks, make sure the fuel pressure is set correctly (WUR).

[area man]

also if you do try to glue it - either pop off valve or the whole air box - make sure you're using proper cement for this kind of plastic. It's low surface energy thermoplastic and theoretically you need something better than JB weld. there are threads on this I believe...

[Jerome74911S]

Originally Posted by Jdub

EDIT: I'd also like to point out (without being mean) that your airbox looks really, really dirty.

I took the pictures after I cleaned it up some. Yes, I know it is terrible. In taking all manners of things apart, I discovered that a PO, who removed the charcoal canister and associated plumbing (almost everything has been striped away), decided, in his wisdom, to connect a fat left-over hose directly from the cooling shroud to the intake next to the pop-off valve. The result was pumping unfiltered air directly into the intake, which no doubt has done wonders for the life of the engine.

I saw this state of affairs when taking a lot of other stuff off of the engine and, needless to say, corrected the problem immediately.

Once I get the area clean, it will stay that way.