Gluing Plastic on Plastic

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My car's air cleaner shroud is made of plastic and a piece broke off. It's a clean break and I should be able to glue it. It will get hot under the hood and the area adjacent to the break is a little grimy. I need to clean it very well and then use the best quality epoxy. What do you recommend for cleaning and prepping the area. Also, what is the best glue for this application. Thanks for your help
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jb wrote:

If it is like any of the underhood black plastic I have seen, forget it. Nothing will bond to it permanently. It isn't just hot and greasy, it is constantly moving. You may be able to patch it with a metal gusset and pop rivets, but it probably won't be leakproof. Dealer price will be outrageous, so you may want to start calling around to junkyards.
-- aem sends...
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My radiator has a plastic top, JB weld has worked for 4 years stopping a leak, but in the cold it can take many days to cure, the colder it is, the longer it takes and JB tech support has no info on cold temp curing, Laquer thinner is used to clean the plastic. There are silicone auto adhesive sealants by maybe 3m, go to an auto store and see what they have.
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Naptha to clean the area, let air dry for an hour, then JB Weld. If you are in the north where it is below 50 F, you could speed up the curing by heating the general area with a hair dryer on low heat every few minutes for about 30 minutes. Then allow another several hours for it to really set up.
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wrote:

Forget the "Hours" time, its days for JB at 20f, I waited because my radiator in under 12 psi and knowing how antifreeze is greasy I knew if I got a leak it would mean complete removal , I have no leak years later. Napha? Does JB say naptha is ok, Alcohol is a no no because of oil in denatured alcohol, the surface must have no residue , laquer thinner is a stronger solvent.
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Utter nonsense, there's no oil in denatured alcohol.
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snipped-for-privacy@milmac.com (Doug Miller) wrote in wrote:

I use denatured alcohol all the time for cleaning.No oil,either. Or you can use 90% isopropyl alcohol,available at CVS pharmacies.
alcohol is a solvent for uncured epoxy.
epoxy cures slower the colder it gets,you need at least 60degF for a decent cure.I like to use a lamp to provide extra heat,it cures faster,which makes it stronger.
--
Jim Yanik
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On Jan 25, 7:27am, snipped-for-privacy@milmac.com (Doug Miller) wrote:

Yes there is its a contaminent in the poison so you cant consume it, JB states to Not use denatured alcohol, but you of course know more than JB weld on how their product performs. Call JB and learn some sense
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No, there isn't. You are clueless as usual.

That contaminant is (usually) methanol, not oil. Look it up.

Quit making stuff up. I just looked at the package in my workshop. It says "for best results use lacquer thinner or acetone" but says NOTHING about denatured alcohol.

Pay attention, fool. I didn't say ANYTHING about what should or shouldn't be used to prep for JB Weld. I said there's no oil in denatured alcohol. There isn't. Look it up.
If you would actually take the trouble to read what you're replying to, and not make up stuff when you have no idea what you're talking about, then you wouldn't look like quite such a fool.
Or maybe not.
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On Jan 25, 9:30am, snipped-for-privacy@milmac.com (Doug Miller) wrote:

Fool? Petroleum Oil, or Naptha is a common ingrediant, there is a reason JB says dont use it as any contaminent will shorten bond life. Brand formulations vary since its a formulation, not a pure solvent, since it varies its not recommended, but you should still use it, I will feel better.
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Yes, fool. You. Fool. You should take this saying to heart: "Better to be silent, and be thought a fool, than to speak and remove all doubt."

Petroleum oil and naphtha [the correct spelling] are not the same thing. And neither one is a "common ingredient" in denatured alcohol. Here, learn something:
http://jwbasecamp.com/Articles/SuperCat2/MSDS.htm (links to the MSDSs for seven common brands of denatured alcohol)
None of them contains petroleum oil, and only one contains any napththa (eight-tenths of one percent).
What *do* you see there as the most common contaminant? Methanol (methyl alcohol), just like I said.

Show me where JB says don't use denatured alcohol. You can't. It doesn't.

Like I said, Ransley, quit making crap up when you don't know, and you won't look like such a fool.
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JB Weld. NOT the 5 minute one because it is half as strong as the 24 hour one. Warm the tubes of epoxy first with a hair dryer, it will come out of tube easier and blend better. I use it on most anything. WW
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JB weld worked great to repair my wife's Jeep windshield washer reservoir but would stick worth anything when I tried to use it on her fan shroud.
Jimmie
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clean with acetone first. try construction adhesive,like Liquid Nails. You may have to put it on pretty thick,covering the seam with a bead of adhesive.It will not look pretty.
--
Jim Yanik
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On 01/24/2010 09:34 PM, jb wrote:

Better get a new one. This may affect your mass airflow sensor and screw up your gas mileage.How did you break it again?
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Van Chocstraw wrote:

top of the engine. Is is in two parts. The rear part holds the 2 air cleaner elements and the 2 air intake snorkels. The part I broke is the shroud that attaches to the air cleaner and covers the front part of the engine. It has no real functionality but just pretties up the compartment and says "AMG" in big letters. The underside has a single plastic post with a spring clip. I pushed a little too hard down on the front edge and that post cracked off clean. After 11 years that plastic has gotten brittle in the heat. It was stupid. I should have been more careful. Anything with a "AMG" logo will cost a fortune and forget the junk yards. It sounds like many of you had good success with JB Weld and I checked AUTOZONE and they carry it.
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so,you ought to be able to make a good thick bead on the backside of it. rough up the plastic before epoxying it.Maybe wind some bare copper wire around the post before epoxying it,as reinforcement. That post,having a spring clip on it,will have some stress on it. You may have to build up more than one batch of JB to make it strong enough.Be sure to give it enugh time to fully cure.
one thing about epoxy;it takes a few -weeks- for it to reach FULL strength. (despite what it says on the package...) you will also find that JB Weld will seem thick,but in curing tends to run(spread out) a bit.Heat makes it cure faster,a good thing for epoxy. I like to use a incandscent lamp to add extra heat,or in summer,just put the workpiece in the car trunk to cure;it gets over 140degF in there,just right for curing epoxy.
I use JB a lot,but I also use a good boat-building thin epoxy(RAKA)along with fillers and glass cloth.Nice thing about the thin epoxy;you can tailor it with the fillers and glass to fit your application.JB is an epoxy already having fillers.But you -can- add more,like chopped fibers,for more strength.

that is one major beef I have about the use of plastic in autos.
I have the same problem with the interior maplight assembly in my 2003 Nissan Sentra.An inside piece that held a spring clip crumbled,and now the assembly doesn't snap into place,it keeps falling down.

So does WalMart,Home Depot,Lowes,Ace Hardware,and lots of other places. Even supermarkets.
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Jim Yanik
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Replace with a K & N filter assembly complete. Prices are reasonable, some filters are serviceable, and the gas mileage and performance will improve on your car. Check at Autozone, NAPA, Manny, Moe, and Jack, Carquest, others.
Joe
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jb wrote:

Epoxy is not good for this, and rarely is super glue (cyanoacrylate).
The best glue varies with the plastic. PVC, ABS, CPVC, and polycarbonate should be repaired with solvent weld, such as lacquer thinner, acetone, MEK, xylene, CPVC cement, or acrylic (plexiglass) cement. Plastics that don't dissolve, such as nylon, polyethylene, and polypropylene (your air cleaner is probably made of the latter) are best repaired through welding (melt groove with soldering iron or wood burning tool, fill groove with identical plastic), but epoxy can often make an adequate mechanical bond if the plastic is roughed up with #60-80 sandpaper and the epoxy reinforced with cloth or gauze (fiberglass, polyester, even wire mesh).
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do_not_spam snipped-for-privacy@my-deja.com wrote:

Or just pop-rivet a hunk of flashing over it until he can find a replacement part at a price he can stand. While JB Weld, epoxy, etc, may work for parts that don't get flexed, the air cleaner/snorkel/scoop is always moving, since the engine flexes on the mounts. Hard to say without seeing it. OP may want to ask over on rec.autos.tech, where they are used to McGyvering solutions to problems like this.
-- aem sends...
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