cracked plastic

WVAhills · Oct 19, 2015

I use JB Weld on the cracks in my JD 4400 hood etc , repaired a big chunk I broke out of my fender with JB Weld...Luv the stuff

varmint · Oct 19, 2015

Harbor Freight sells a plastic "welding" kit that works pretty well, but you may still want to use Bondo and some paint. Or, I thought the aluminum pop rivets and a backer sounded workable.

darrenjttu · Oct 19, 2015

I used a fiberglass kit from auto zone for 20 bucks. It worked great. I bulked up some flimsy areas with the left overs. I will use this from now on. It's the strongest stuff I have ever used. Dries very fast too.

PILOON · Oct 20, 2015

When a crack develops the first and most important thing is to stop drill that crack.

That is you drill a small hole, 1/8-3/16" at the end of the crack and de burr the edges otherwise the crack will grow.
That was the standard 'fix' for cracked light aircraft windshields made of plexiglass.
It was also used should any aluminum skins develop cracks as well.

On today's cars with plastic bumper 'covers' it is ever so easy to find the occasional crack or tear from curbs and low bumpers.
Stop drilling those bumper cracks can save U very costly replacements.
If not stop drilled the vibration caused by high speed flutter can grow that small crack to the point of non repair.

WVAhills · Oct 23, 2015

I have a John Deere 4400 and it has a flimsy plastic hood which I have had crack on different occasions and I ALWAYS use JB Weld and it bonds very well and is easier to use ,if the hood cracks again I can assure you it is not the JB Weld that cracks it is a new crack elsewhere in the hood , the older tractors like mine circa 1999 ,2000 have a less impact resistant plastic then the newer tractors of today. I have had the hood crack if the hood was dropped and instead not carefully closed . The hoods for John Deere today it appears they are mixing a thermo plastic rubber in with the plastic when the hoods are molded , this is called impact plastic I can see a HUGE difference on my new John Deere X 758 Signature series as compared to my old JD 4400 in quality and flexibility. As far as ALL tractors having plastic hoods this is not true , the Massey Ferguson tractors at least the larger ones I know have a metal hood.

muddstopper · Oct 23, 2015

I welded up the entire instrument panel as well as a hole in the fuel tank on a tn75 new holland with nothing but a soldering iron. If you take one of those high wattage pencil type soldering irons with a flat tip and turn the tip on edge, you can melt the plastic back together. I turn the tip on edge, run it the length of the crack, applying just enough pressure to make a small vee along the crack. You have to go slow enough to melt the plastic, but fast enough so that you dont burn the plastic. Then you can take zip ties and take the flat part of the tip and mash the ziptie into the vee groove, sort of like gas or tig welding. Once the weld is complete, you can take a sander and smooth out the weld, just like grinding a weld smooth on metal. I weld up my chicken waterers regularly with a soldering iron. Zip ties make excellent filler material, but for the tractor fuel tank, I went to the junk yard and cut out a piece of a car gas tank to use as filler. Took a little time, but beat the $400 price tag of a new fuel tank.

Billrog · Oct 23, 2015

Best results I've had are with fiberglass resin with matting on the back then you can finish the face side with body filler for painting. It will stick just fine to plastic as I did the propane tank cover for our trailer. The hood of my dump truck was all cracked up around the head lights and I did it as well before painting.

bumperm · Oct 24, 2015

There are two basic types of resin (the plastic used with fiberglass cloth), polyester and epoxy. When you buy an inexpensive fiberglass repair kit, it will have polyester resin as that's much less expensive. However, polyester does not bond nearly as well to many materials as does epoxy, nor is it as strong as epoxy.
BTW, "Bondo" is a polyester filler.

Test first to make sure epoxy will bond to the plastic - you can even use 5 minute epoxy glue (or any epoxy resin for this (if JB Weld, an epoxy resin with filler, works, then you're good to go). Sand the area to be repaired on the inside. Clean with a solvent like PrepSol or whatever and apply fiberglass with epoxy resin.