Epoxy-reinforced intake

Okay, so our Cooper S has a small crack in the plastic intake tube that runs from the throttle body to the supercharger inlet. Apparantly this is a common problem and easily remedied with a new $100 tube. Eeep. The tube lives right behind the radiator and can't be seen until you remove the MFE (Modular Front End) So I'd prefer not to do this again anytime soon.

So, I'd like to reinforce the replacement unit. I was thinking of coating the suspect area in epoxy and laying in some fiberglass mesh. A skim coat of epoxy once the first run dries and call it good. I'll have to find an epoxy that will tolerate a little flex and is not as brittle as JB weld, just in case this thing sees some kind of flexing in use. Don't know for sure what type of plastic it is, maybe ABS but not certain.

Thoughts on type of epoxy or specific procedures for the process??

Use polyester instead of epoxy. If it's ABS, then ABS cement should work.

There's not any aftermarket remedies for this, like maybe a steel or aluminum part?

I've had good luck with the black ABS cement they sell in the plumbing dept. It's used for gluing ABS pipe together. I use it with fiberglass cloth so the ABS cement is used in place of the resin. Seems to hold up quite well for me. Not sure on your part of course.

unfortunately no aftermarket solutions seem to be available. The tube fits in a very specific space and is shaped apropriately. Unless you get into heavily modifying the throttle body and then the superchager, I don't think there's much improvement over the stock piece. Other than strengthening the plastic.

browsing the epoxy aisle and picking a direction was about what I had in mind, but I think testing the ABS glue on the old part may be worth a try. Where might I find the polyester that Zomby speaks of?

Your standard resin sold at most any auto parts store is Polyester. That's what he is refering to. It's still a two part mix but you only need to use a small amount of the hardner to activate the resin. With epoxy you usually use equal amounts.

Before you go to "fixing" the broken part, here's some food for thought. Why did the part break? How can you prevent it from breaking again? If it does break again, will it cause further problems? Is the replacement part from BMW the same part number, or has it possibly been superceded by a "fixed" part?

I don't know anything about the part in question, but patching a plastic intake piece that broke from regular usage sure sounds like a recipe for another failure of the same type. It sure would be a bummer to spend 5 hours fixing it with a $7 patch just to break it in 5000 miles and find yourself spending another 3 hours to redo the job with the $100 part.

Bryce

how about a nice wrap in carbon fibre and resin?

ultraclyde wrote: Don't know for sure what type of plastic it is, maybe ABS but not certain. Thoughts on type of epoxy or specific procedures for the process??

Oh, oh I know the answer to this question. The material for plastic intake manifiods is nylon, typically nylon 6 or nylon 6/6. It is more heat resistant and more chemical resistant than ABS. This second property makes it more difficult to bond together. Epoxy will bond to it but you will need to abrade the surface a bit before attempting the repair. Clean and degrease the surface completely before abrading it to avoid driving grease or oil into the area you are trying to repair.

JB Weld. There's not much it can't "fix."

In reply to jimbbski:

All the epoxy resin I have used was not an equal mix. The stuff I have been using from US Composites is a 3 to 1 mix.

Nashco, you are absolutely right. That's why my plan is purchase a new part and reinforce the suspect area before installation to hopefully prevent early failure. the cause looks to be crappy manufacturing and too-thin plastic in an area that experiences a lot of heat flux. Seriously, the casting and work on this piece is about par for late 80s GM work, not up to BMWs normal standards.

Thanks wawazat, I actually have a polymer chemistry degree but haven't worked with the auto sector. That pretty much tells me what I need to know. Abrasion is a definite part of the plan.

I considered carbon and resin, but it's probablt outside my price range for this. Plus you never see the thing so I couldn't brag about it.

If you go with something like a fiberglass wrap, then I see no reason not to do it to the old part. No need to buy a new part if you're going that far.

Also - might consider rhino lining. I'm not sure how it reacts to heat, but it is flexible, seals 100%, and is strong.