Airbox repair question(s)

[LWJ]

Yes. I have a cracked airbox on my SC. Do I fix it or buy another?

The highly esteemed John Walker says to just suck it up and buy one.

The forum is full of people who used JB Weld successfully.

I keep thinking that JB Weld is not flexible and will crack at the point of adhesion. I think a high-temp RTV or similar would be better.

What does the brain trust say?

Thanks in advance,
Larry

[fanaudical]

Be warned: Discussing airbox repair is almost like discussing motor oil selection...

I think repair approach is dependent on the damage. What's wrong with it?
e
Adhesive selection for this stuff is tricky. Ideally, you need an adhesive that also acts as a solvent for the substrate. I have used some epoxy specifically made for bonding polypropylene and polyethylene to fix small cracks; this has held up well.

I have often wondered if something like the POR15 gas tank sealant stuff would be useful for sealing an air-box (paint a heavy coat on the outside).

[BlueWing]

Has anyone tried any of the ultraviolet light cured adhesives? There are some consumer available products now. I only saw some ads about a low end stuff but is there anything in between Seen on TV and like a dental quality product.

Terry

[rwest]

My very, very unscientific opinion is that over the years the plastic gets "brittle" as well and will just keep cracking and easier. I say suck it up and go new.

[LWJ]

Fanudical, I like it. Solvent is a great approach that I had not considered. Motor oil. Got it!

[MARISOL78sc]

Originally Posted by rwest

my very, very unscientific opinion is that over the years the plastic gets "brittle" as well and will just keep cracking and easier. I say suck it up and go new.

+1

[LWJ]

Rutager, I think you are correct. Thanks for talking me down from a crummy repair job. I love my car and like driving it better than looking at it on jack stands in my garage!

[rwest]

Originally Posted by LWJ

Rutager, I think you are correct. Thanks for talking me down from a crummy repair job. I love my car and like driving it better than looking at it on jack stands in my garage!

Went through the same thing last year, guy hates to spent $500 on something that he thinks he could fix for $5! I'm very happy I just bit the bullet and went new. I suspect fresh plastic would also take the occasional minor back fire without incident.

[jason2guy]

i had the same issue and decided to repair it so i bought some 3m two part adhesive that was recommended on this board, well by the time it came to use the 3m stuff i think it expired because it looked like cottage cheese when i mixed it up. luckily i had jb weld on hand and used that- and not very sparingly i might add, then i nut and bolted the box together where the original screws were. its been about a year and its held up well
mine was cracked underneath where the two parts come together and is out of view when installed

[groovydude]

If your leak is at the joint between the two halves, like most are (it seems to me), then I don't think it's an issue of brittle plastic, but of failed glue. There is another thread about this on here where a plastic expert posts swearing that this particular kind of plastic is impossible to glue (he sounds like he knows what he's talking about). That said, many people claim to get good results from jb weld. I tried this approach, and it seemed to work (I got an air tight seal), but in the end I bit the bullet and bought a new box. The thing is such a pain to remove I felt it was worth the expense rather than spend another day in agony a year or two from now and still be out $500. If you're going to glue, I would try completely separating the two halves first, clean with alchohol, then weld them together and use new nuts & bolts. It sounds like this is what Jason did (?). I spread the weld outside mine already assembled and it's messy and ugly.

[gazzerr]

I wasn't confident I could get a decent repair that would last either so I bought a new airbox too. I'm no artist though. Some guys can fix anything and make it look like new.

[wayne robson]

Thought i would let others know ,re repairs to any plastic, fiberglass,
steel, aluminium,wood, masonry,etc. Born in New Zealand have
had many years experience in Boats and Boat building, in case you dont know
every New Zealander owns a boat,and has held Americas cup yacht racing for many years.
Repairs to air box ,the only proper repair is to use is a polyester resin, catalyst,
fiberglass and dynal weve repair kit, it entails mixing two pot resin, brushing or
spraying first coat on,laying weve cloth, then another coat of resin,then letting it dry,
sanding lightly,then another one or two coats of resin,depending on strength required
final sanding.This will give an unbelievable amount of strength ,and will never
let go.

[theiceman]

funny how people say it cant be glued yet when you buy a brand new one you can see the glue running down from when they originally built it. I think mine was pink in colour.

[mhackney]

A new Genuine Porsche air box for my 83 Cab cost $223.75 from our host 911-110-904-01-OEM

I got one in May and waiting to put it on. At that price, I could not justify the time to attempt a repair and risk having it fail again in the near future.

The new ones are indeed glued. The new one has a milky white appearance. It almost looks like glue stick and seems to be a thermoplastic.

My original one failed at the glued seem, I don't think it backfired (not during my watch anyway) but the adhesive just gave up the ghost after 33 years.

[timmy2]

Large port 44mm air box is $452....
Twice the price! ????

[Bob Kontak]

Originally Posted by mhackney

A new Genuine Porsche air box for my 83 Cab cost $223.75 from our host 911-110-904-01-OEM

That is an outstanding price.

[mhackney]

@Bob, yes it is. I just hope it works! (I cross referenced the part multiple times to be sure and now that I have it in-house along with the injector sleeves and other parts, it looks correct.)

[gazzerr]

You got a deal on that. I paid close to $500 for mine. Good info on the fiberglass. Unfortunately I'm more of a butcher as opposed to a surgeon. .

[Bob Kontak]

Originally Posted by gazzerr

You got a deal on that. I paid close to $500 for mine. Good info on the fiberglass. Unfortunately I'm more of a butcher as opposed to a surgeon. .

Even at $500, there is big work to pull it in a later SC.

Then you get to put it back together and then hope it works. Surgeon or butcher.

On the upside, if it does not work then your time is cut in half and it will only take one weekend instead of two for round two.

The guys that say "Four hours" are either very experienced or lying. It is a job.

[Jdub]

You want to know the airbox is 100% when you start evaluating other issues that might crop up, god forbid. I would suck it up as the Esteemed one has said.

Question for you: Were you running a pop-off valve and will you/won't you in the future?

By the way, my '78 came from Continental Audi/Porsche in Beaverton (Lake Oswego owner).