What do I repair a Mondial bumper with?

Hey Gang,
The thread on bumper refinishing over in the 308 section got me motivated. I have a chunk about 1" long taken out of the leading edge of the Mondial front bumper. (Like the car bumped something lightly). What would be the best material with which to fill this? I was thinking one of those body fillers with strands of fiberglass in it. Not sure what I can use that will STAY. Thoughts?

Sorry for the somewhat fuzzy pic. I thought the thing was in focus based on the tiny screen on the camera!

Birdman
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A 3.2 bumper.....

I think the fiberglass sounds like the way to go.

 

There are two ways to fix your Urethane bumper.

1.)Most body shops supply stores carry a two part epoxy urethane bumper repair kit. It mixes 1 to 1 and you smear it on like body putty, but it will stay rubbery. When it dries, sand it off to the level of the rest of the bumper. The difficulty is it stays rubbery for a few days, and is difficult to sand, but if you let it dry and use a hard block, it’s possible. It most likely will take 2 or 3 applications to build it to the correct level. When you’re done, repaint with Simms bumper paint.
2.)Pick up some two part black Urethane build a RTV silicone mold (not the stuff you buy at the auto store) (best to use another non damaged portion of the bumper for molding purposes). Mix the urethane and pour it into the mold which is attached to the bumper. Let dry 24 hours and sand off it will probably take 2 coats to build up to the correct height. When you’re done, repaint with Simms bumper paint.

If you need to source product, want me to mold it for you, or other tips PM me and I’ll be happy to help

 

The bumper isn't rubbery. It feels like hard plastic. I don't think I need a repair which is rubbery.

Birdman

 

For something like this I would recommend JB Weld (which is a two part epoxy) but it is very solid and would better match the texture of your bumper as opposed to Bondo (another 2PE). Prime and then paint.

 

It’s made with Urethane something like 80 to 85 A Durometer. Over the last 20x years it has hardened probably a little more than when it was manufactured. To fix it properly, you will need something that has a small amount of flex to it. Epoxy which isn’t formulated for urethane bumpers will be too hard and eventually crack. Urethane is a two part liquid, which will begin to harden within 5 min of mixing, but will take 24 hours to fully cure out. During this time, it progresses from a liquid similar to molasses, to a hard rubbery plastic. If you attempt to sand it prior to a full cure, it is almost impossible.

 

Would this compound work on a 308 bumber?

 

JB-Weld is the answer. Use it like body putty and fill in the divit. You're going to have to refinish the bumper any way so a filler is the answer. Anything 'silicone' will not hold paint.

rick
'79 308GTB, refinished bumpers
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Can you paint this stuff?

Frankly, I'm liking the JB Weld idea!

As a secordary question, what do I use to remove all traces of Armor All and whatever goop has been put on this thing over the years? I wiped it down with natured alcohol but I doubt that will get everything off so when I paint it, the paint will stick!

Thanks

Birdman

 

Dan T
Would this compound work on a 308 bumper?

Yes, the 308’s are also Urethane.

Rolindsay

The silicone is only a molding material to reproduce the exact contour of the part you’re trying to recreate. After you’ve created the silicone mold, you then pour urethane in the mold which is attached to the bumper, when it dries, you have an exact duplicate of the bumper, with little sanding. The silicone mold is expendable.

Birdman,

Yes, if you can paint the original bumper, (almost every car today has painted urethane bumper covers) you can repaint the repaired section. Simms bumper re-coater is designed for this exact repair. Not exactly sure what the compound is, but it works well. In order to clean the oil, bugs, tar and grease, use a wax and grease remover, body shop supply stores will carry it in quarts.

 

Don't use JB weld, it's too rigid. There's a good chance it will pop out in a year or two.

Over the phone I told you that there's a flexable body filler made for bumpers, fibreglass panels,& other plastic trim like air dams.

It's SEM flexable filler, available from most auto body supply stores. Its the right durometer, feels hard to the touch, but has just enough give so it will flex with the bumper.

SEM also makes a true urethane based bumper repair filler, but it comes in a 2-part cartridge with a special mixing nozzle & requires a special gun to dispense it. Hmm, probably could manually force out equal parts from each side of the cartridge & manually mix them. Isn't cheap tho, believe a cartridge runs about $50.

Hmm,
While writing this I was reading jh355's post. He's talking about making a mold using the 2-part RTV i use for making my molds. I have a Devcon 2-part polyurethane that I use for casting 'rubber' parts that could be used to mold onto the bumper.

Give me a call before you committ to a repair.

 

Too late, I did it with JB Weld. Frankly this is not that big a ding and to spend a ton of time and money running around to find this funky filler wasn't worth the hassle. I still can't see how this needs a flexible filler. The plastic of the bumper is as hard as fiberglass. There is no flex to it at all. If you rap on it with your knuckles it is like hitting a piece of hardwood. The fenders of the car have more flex than this piece.

I cut some tiny grooves into the hole with my mini-grinder and a 1" cut off wheel (about 1mm thick) to give the JB Weld a better surface to grab. I globbed some JB Weld on there, then wrapped a piece of wide plastic clear box tape around the repair to quasi-mold it to the curve of the bumper. I let it cure and pulled the tape off. Looks good. I'll give it a good sanding to blend it, and paint the whole bumper. (I used bondo to fill the thousands of pinhead-sized pock-marks from little stones in the front). Job done!

Thank you all for the ideas. If the JB Weld falls out, I guess you were right and I'll have to fill it again!

Birdman

 

(in a small Mike Tyson voice.)

MONDIAL BUMPERS ARE FIBERGLASS.....!

(USA 308's urethane)

So, fix it like a surfboard, and have a nice drive.
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If that doesn't hold, you can always use Wisconsin Chrome (Duct Tape).

 

Here's a couple pics, showing the glob with tape over it. And afterwards, rough sanded. (It will be fine sanded when I sand the whole unit before painting.)

The gray area is the repair, the white is where I have sanded through the paint on the pumper to the plastic.

Birdman
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Ah HA! I knew it! It looked like fiberglass when I took the grinder to it! The white is probably primer.

 

No, the white is gelcoat. My old & new Euro bumpers have white gelcoat on the surface.

So your original idea of fibreglass filled bondo would have been the best choice other than just repairing w/new fibreglass.

 

D'oh!

Well, I'm sure JB Weld is just as strong as fiberglass-filled bondo, if not stronger.

I once JB Welded a kitchen sink spigot at our house in Maine just to get us through the summer until I could get a new one up there. (The house is pretty far from a good plumbing place). The repair lasted 3 years, until I finally got tired of looking at it and replaced the spigot!

Birdman

 

No Bondo,,, this is not a 1966 Chevy Impala!

Bird used Epoxy, which is fine for fiberglass.
But,,,,,,, Polyester Resin and fiberglass cloth, or microballon filler, would be more correct.

Ciao.

(I actually like the earily Mondi bumpers better, more pointy.)
Pointy Cars rule!

 

Yes you can paint it but you need to prime it.

Denatured Alcohol is what bodyshops use to get rid of wax, silicone, etc. so you should be ok there. Don't put too much JB-Weld just enough to sit flush with the rest of the plastic bumper piece. Give it 24 hours to cure.

If you need to even-out the JB-Weld to your bumper (You don't want a hump of epoxy sitting on top of your bumper) take a medium-fine git paper (300 grit) and grind it down (I use a rotary sander), then go over with a couple of finer git sand papers to remove sanding lines. Prime. If you see any unevenness, this is where I would consider using a super-fine layer of bondo (although if you sanded carefully you shouldn't need it). The JB-Weld is great for rigidity and structural pieces (Bondo better for cosmetics) JB-Weld doesn't lend itself to filling cosmetic dips or gaps, it's just a little too thick.

 

No Bondo ever...

Use SEM 42003-42043 HIGH BUILD PRIMER SURFACER, even comes in a spray can. For pockmarks and pits, smash it in with your finger prior to drying.
SEM also makes flexable paint for you USA 308 guys..


Like tri said, Remove all Wax and Grease with Wax and Grease remover.

If you want to go to the "Bondo" , don't buy Bondo brand ****, buy Evercoat..

 

Quote of the week!

 

Umm, arguable, fibreglass with a binder becomes a composite material, typically 3x - 5x the strength of the binder alone.

JB Weld is just a form of slow set epoxy with fillers, sets up very very hard, resistant to a lot of chemicals, more heat resistant than most other epoxies, adheres to a lot of things, but is inflexable, has little tensile strength, & is very brittle.

I 've used & like Weathercoat's sprayable filler.
Also, 3M makes an excellent line of body fillers, as does SEM. All are better (smooth out easier, can be feathered, longer working time, easier to sand. etc.) than HW & AZ/PepBoys Bondo brand... There's a reason that auto body shops don't sell the Bondo brand...

 

Good point. And I didn't know you could get primer sealer in a can but that is a better solution. I would never want to encourage using Bondo under any circumstances. Thanks.

 

Why? Ferraris are full of bondo from the factory!