CIS Airbox Pop Off Valve Epoxy

[Jay Laifman]

I am confused on the epoxy. I've seen a lot of comments on what epoxy to use - with lots of people swearing by their results - mostly JB Weld and Loctite Epoxy Cups.

The problem is that I've seen multiple comments that the airbox and the valve are made of polyethylene or polypropylene. And when I look at the various epoxies mentioned, including JB Weld and Loctite Epoxy Cups, they all specifically say that they won't work well with polyethylene or polypropylene.

When I search for an epoxy for that material, I come up with 3M Scotch-Weld Structural Plastic Adhesive DP8005 or Loctite Super Glue Plastics Bonding System. The DP8005 one seems like it needs a whole tool and nozzles to work. And the Loctite one is a fast thin super glue, that also doesn't seem quite right.

I want to do this right, and not have to worry about future leaks. Does anyone have a correct answer here?

Is it possible that the box/valve is not made of polyethylene or polypropylene?

[Jay Laifman]

I should add that I'd just use the 3M DP8005. But it seems I've found it only in a special tube that needs some sort of tool and nozzle to use - and it's pretty expensive for this single use.

[Showdown]

Many moons ago I had a pop off valve that was made of glass reinforced nylon, no epoxy or other regular adhesive will bond nylon effectively and you must use 3M DP8910. And yes, it’s very expensive and requires a special applicator, but there’s no way around that.

[fanaudical]

Look for "Loctite Plastic Welder" or "Plastic Bonder" epoxy - should be readily available.

Some relevant other threads:

Polyolefin plastic

83 sc air box

[Jay Laifman]

Thanks to all.

I read all the various links and their sublinks. I think I'm going to use the 3M DP8005 as someone else did - but pushing out with two screwdrivers, and mixing and using like normal epoxy.

I also note that Loctite "Plastic Bonder" spec sheet says not recommended for polyethylene or polypropylene.
https://dm.henkel-dam.com/is/content/henkel/tds-us-loctite-epoxy-plastic-5-min-final

But Permatex's "Plastic Welder" does say it works on them. So I might use that one.

Update. I broke down and bought the 3M product and one of their dispensing guns. So I'll have one to loan out if anyone else ends up needing one.

[fanaudical]

None of the air boxes that I've had in my garage are polypropylene or polyethylene. The DP8005 is still a good choice. 3M makes numerous awesome adhesives - spending money on that dispense gun is a good investment.

[Jay Laifman]

Here is new information. I just communicated with APA that makes the URO pop off valve. They said the valve itself is made from plastic material called PA6, which is a nylon-based polyamide. So what epoxy works on that?

[Showdown]

Does nobody read, 3M DP 8910 is a nylon specific adhesive. That’s what you need, epoxy won’t help you.

[Jay Laifman]

Thanks! But does 8910 work on polypropylene or polyethylene for the airbox? Or whatever the airbox is made of. I see that fanaudical says it is something else, and others online say it is.

I have just looked at the 3M data on 8910 and I'm not seeing if it sticks to polypropylene or polyethylene.

[pmax]

Originally Posted by Jay Laifman

...

Is it possible that the box/valve is not made of polyethylene or polypropylene?

The material used could have changed.

If you have both new and old boxes in hand, could you post pics of them side by side ? It is hard to tell from online pics but the new ones do look slightly "off color" with a reddish hue whereas the original boxes are charcoal black.

[Jay Laifman]

Mine is 25 years old or so. When I got it, I know they had to look all over the place, and it was one of the last ones that Porsche had. So it's whatever they used to have.

[Jay Laifman]

FYI, I just spoke to 3M. They said that since the nylon based material is the hardest to bond to, that I should use DP8910. But they still said that the bond to the air box may not last as long as the bond to the pop off valve. They did not have anything else that might be better.

https://multimedia.3m.com/mws/media/2365943O/3M-Scotch-Weld-Nylon-Bonder-Structural-Adhesive-DP8910NS.pdf?pif=B5005281015

[914efi]

I put one in 20 years ago, I think I have had to re-do it twice which it not a huge deal.

The most recent time I used Hardman D-85 urethane epoxy we use at work for nylon among other things. I think it is pretty basic stuff. One thing i did this time was to undercut the OD of the valve so it is keyed in better. The airbox can flex but the valve is very solid. I like the urethane because it can flex a bit, this one expands a bit as it cures so it tends to fill gaps.

The gasoline fumes can take a toll on the epoxy for sure.

[EC900]

It would have been nice if they designed these POV’s to screw on like a gas cap threaded is such a manner so it tightens and centers in the proper orientation.

That 3M data sheet has some holding strength values, even on the weakest or challenging substrate, the force needed for hold probably exceeds the POV spring rate which if I estimate is probably 2-3 lbs.

I agree with making an indentation of sorts to “key in” an undercut for the adhesive to grip.

One particular you-tuber explained the drilling of the opening. Using a hole saw with a drill bit arbor going into a predetermined pilot hole is essential so the hole saw doesn’t wander and isn’t cut a mm larger or out of round.

[Funracer]

Originally Posted by fanaudical

Look for "Loctite Plastic Welder" or "Plastic Bonder" epoxy - should be readily available.

Some relevant other threads:

Polyolefin plastic

83 sc air box

I used the Loctite Plastic Bonder a couple of months ago on my new pop-off. Stuff is super viscous and super sticky and also starts to harden in about 10 minutes. Plenty of time to do the job just be ready to go after you mix.