Sealing up CIS air box - while still on the car?

[fanaudical]

My CIS air box seems to be leaking quite a bit along the seams that join the upper and lower sections. I confirmed this using the vacuum-cleaner-in-reverse-with-some-soapy-water trick (which worked great!). I have investigated the rest of the connections and they all appear to be tight.

This is a weird situation: This is a newly rebuilt motor with all new injector sleeves, seals, runner-to-airbox tubes, etc. Looks like the air box seams opened up shortly after first start-up. (I had bubble-checked the air box after cleaning it up prior to rebuild. Obviously, I did a poor job.)

To me, it looks like it's possible to remove all the screws joining the two halves together and disassemble the thing while it is in the car (without pulling the entire CIS system). Has anybody successfully done this?

Thanks for the help.

[James Brown]

no but you can remove the whole plenum after removing the runners and most of the upper components in he car. After that you can get some epoxy on it in those hard to get places and verify that it is air tight, and put a pop off valve in it if it doesn't have one.

[timmy2]

Definitely need to remove it from the car.
Even though the seam is leaking it is still glued together in a lot of places internally.
The 2 halves are joined with a square shaped tongue and groove all around the perimeter.

[fanaudical]

OK - Thanks for the info. I guess I'll order up intake gaskets before popping that apart.

I do have a pop-off valve, but no longer sure that installing it was a good idea after reading Pete Z's explanation of some common air box misconceptions.

[Daviboy]

Dont even bother trying to repair it I had the axcat same problem and tried numerous ways of 'glueing' the airbox back together all of them failed. Do yourself a favour and buy a new one or you will contiually be chasing vacuum leaks. Try and find an aluminium one they are rare but the best and you will never need to worry about cracking.

[fanaudical]

Does anybody know what plastic/resin the air box is made from? ABS? Other?

[fanaudical]

Sorry - Should have searched before asking the question. Another thread indicates that it is polypropylene or polyethylene (in which case I might be able to get this thing welded to seal). I'll update whatever it is I eventually do.

[JT]

Did you ever get it sealed properly? If so, what did you use? I heard Sashco Lexel will work.

[fanaudical]

I haven't sealed this up yet; it's been running pretty well in the good weather lately and so I've been enjoying it. I'll probably tackle this fall.

[john walker's workshop]

if it split cleanly along the tongue and groove seam, you can use glues rated PP. they bond/melt the type of plastic used for the airbox. HPPE glue, it think that's correct, works too. (maybe it's HTTP). if it's busted beyond the seam, forget it, new box.

[JT]

Using the vacuum up the tailpipe vac leak test, i was getting bubbles around the seam. The box is out, there are no cracks, the screws are out, but the box won't separate. That tells me it was resealed once before as there is some gummy stuff (sorry I'm not too good sealing compounds) at the bottom of the screw threads. Some of the weren't completely tight. Can I just put them back - tight, and put some glue/sealer along the edges?

[john walker's workshop]

try some slightly larger sheet metal screws for a good bite.

[JT]

Will do. Any sealer/glue on the edges?

Thanks,

[Paulporsche]

Originally Posted by john walker's workshop

if it split cleanly along the tongue and groove seam, you can use glues rated PP. they bond/melt the type of plastic used for the airbox. HPPE glue, it think that's correct, works too. (maybe it's HTTP). if it's busted beyond the seam, forget it, new box.

I think what John means is HDPE (high density polyethlene) adhesive.

[fanaudical]

Updating with some recent testing. I eventually pulled the CIS off the car to fix the airbox. Let's just say that gravity always wins and the original airbox shattered into a few pieces. I picked up a used airbox with similar sealing issues along the seam.

I have determined that the airbox is not polypro or polyethylene (is most likely PPS or polyphenylene sulfide). Most of the adhesives for PP/HDPE also work for PPS (but there should be more adhesive options for PPS).

[patkeefe]

I have blown up some airboxes with my turbo, and a few backfires, which resulted in my doing some substantial airbox testing. I have found that plastic airboxes leak. Maybe not when they were new, but they do now. I will go so far as to say if you have an airbox, it leaks. Further, if it leaks, it is virtually not seal-able.