is this far enough??
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TECH Apprentice
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From: College Station, Texas
Absolutely don't use bondo or fiberglass. If it's only a couple small areas, you could use a filler designed for plastic bumpers. I've been using Dominion sure seal semi rigid plastic surgery for ever (over 20 yrs). Make sure you've sanded out the scratches the best you can and then use a good plastic spreader and spread it over the area as smooth as you can. Also make sure you have sanded the whole area with 150 grit paper before the application. You don't really want to be filling scratches that are coarser than 150, especially if you fill over any painted area, which you shouldn't really, unless the bumper has a really thick build up of paint and can't be feathered out easily. Anyway, that's what I would do if I wasn't going to replace the bumper. See what your bodyshop has to say, maybe they have some better advice. 
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I know fiberglass filler works and if you spread it on the whole thing then sand the fiber glass wont crack as easy but if the plastic cra ks you wont see it because the fiber glass is over if. I have not used the 3m plastic filler but most 3m stuff is good.
On The Tree
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What are your plans for getting the bumper painted? If you were having the bodyshop paint it, then perhaps you could get them to give you a deal on repairing those cracks. If they only charge you a half hour to one hour labor, it might be similar to going out and buying the repair material yourself. And as far as using fiber glass or bondo goes, it would not be impossible, but they have absolutely no flex whatsoever and would be susceptible to cracking or falling off if the bumper gets bumped again. And really, to do it properly, you should use an adhesion promoter on the sanded area first, before applying filler. And just to compare fiber glass and your plastic frt bumper, think about the difference between a ss hood and your plastic bumper. Imagine taking a mini sledge hammer to the corner of your ss hood and also to the bumper cover. The hood is going to shatter, yet the bumper will absorb alot of the impact and perhaps just have paint damage. Anyways, just my opinion, do your own research.
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Thanks! The deal with the shop was I am sanding the cracks down till they are gone, then go up to 600 (also doing rear cover mirrors and headlight lids) and they will re shoot them. Once I sand it the best I can I'll go to them and mention all of these suggestions to see what we can work out, thanks for everyones inputs!
Use 3M autotrix ureathane filler. It mixes like bondo but stays flexible. I will try to find the part number later tonight. I used it on a Formula bumper I did last year and it works great.
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I am a painter in new lenox il i use this flexible 3m glue the number is 05887 it is a 2 part glue substance stays flexable. Sands like a dream. BEFORE U APPLY IT u MUST clean it with a general cleaning solvent. Then use TPO adhesion promoter ( any body supply store has it) apply your glue sand it and your ready for primer. If u do not use the adhesion promoter the glue will not stick. I haven't had a come back with this procedure in 4 years.
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Verdad Gallardo Forgot to say this has to be over sanded plastic it will not stick to paint. Never never ever never use bondo or fiberglass on a plastic bumper. Only kind of filler to use is glaze for any pin holes. Need any help just pm me
Staging Lane
Joined: Feb 2012
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From: Spring Grove PA
I just went threw the same thing when I got my car painted I sanded all the paint off the whole bumper down to the yellow plastic it was tedious and time consuming but the finished product was well worth the prep you can't see any spider cracks and looks great.
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Did you use any of the products suggested or just normal paint steps? Were you able to completely sand the cracks or just partially?
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Ive been pretty busy and can only sand about an hour every day, so this is all ive gotten done in three days. The cracks in the "nostril" of the bumper are my big concern for now. I stayed on them for about 25 minutes strait and as i went the smaller ones went away and the larger ones are getting widder so they cant be too much deeper. Thanks for everybodys comments!
Teching In
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gone far enough Hello, I saw in your pics the stress cracks or spiderwebbing. USUALLY it is just the paint that gets cracked. In the pics it looks like the bumper has cracks BUT it is just where the cracks in the paint have let in moisture or other contaminents while driving. You should be fine sanding to the plastic, yellow bumper and then plastic prime the bumper follow with a urethane primer. You will see as soon as you prime if the cracks are gone. 99% of the time here at our shop the cracks are just in the factory paint and undercoat. Good luck. Ron