View Full Version : bondo is not sticking..

02-12-2012, 04:36 PM
hello guys,
for the first time, i tried using bondo to fix some cracks on my bumper.
At autozone, i bought the one that you have to mix the hardner seperately.
I did my best to mix the right ratio but it's not working.. :(
bondo just peels off as if it's a clay. i gave it more than 20 min of drying time (instruction says 20 min to dry).
What did i do wrong? too much hardner?

02-12-2012, 04:49 PM
1 Is the bumper abs plasitc if so plastic weld it
2 u have to sand till there is no paint left to get bondo to stick it will not stick unless u do that.
3 1 inch of hardener to every golfball size of bondo
4 fold the bondo do not stir make sure there is no lines in the mix it has to be evenly mixed
5 if its cold out side use more hardener ,If its room temp refeer back to 3,if its hot use less hardener humidity and temp can affect the bondo
6 put this in the small qs thread cuse there about to burn u

02-12-2012, 04:50 PM
ok...... so.
you do need a certain pitch of peach/pink. i think what is wrong is you have no idea what you are doing. how did you prep the surface? how much bondo are you using?

02-12-2012, 04:56 PM
if you have the bondo brand scraper, it should be a sort of salmon pink color, just make sure the bondo is the same color as that and it should harden fine.

02-12-2012, 04:58 PM
i didnt know theres a qs thread.. lol sorry
i agree that i have no idea what im doing lol

The way i prepped, i used rough sand paper to sand down the surface until its smooth.
mixed about half size of my thumb with ~4-5drops of hardner.
The bondo was pretty soft after drying time.

bondo was pinkish color like above described

02-12-2012, 05:10 PM
my problem might be not applying the bondo on the surface correctly.
Tips on this please? mine didint come with the scraper?

02-12-2012, 05:13 PM
If the bumper is urethane or abs plastic you need to use 3m plastic weld

02-12-2012, 05:43 PM
Yup like all said above..Can't bondo to directly to ABS/urethane (for example 180sx type x bumper). One way that may work is to get it sanded, epoxy prime, then filler over the epoxy. Or plastic weld. Also, if you have it down to bare ABS you really should give it a coat of adhesion promoter to help whatever paint you are going to apply schtick to it.

Also, check out 3m, lord fusor, SEM as they do make some plastic weld/filler epoxies for fixing bumpers.

02-12-2012, 05:44 PM
mixed about half size of my thumb with ~4-5drops of hardner.
The bondo was pretty soft after drying time.

post up a picture of what you bought. the hardener isn't liquid. so when you say drops it makes me think you got the wrong stuff

02-12-2012, 05:51 PM
post up a picture of what you bought. the hardener isn't liquid. so when you say drops it makes me think you got the wrong stuff

I have had "cheap" bondo that the hardener separated and it needed to tbe kneaded in the tube to get it back to form. The seperated material was very watery. Cheap shit....now I use evercoat rage extreme.

02-12-2012, 05:55 PM
The bumper is fiberglass, aftermarket.
This is it: 3M/3 oz. Bondo professional glazing and spot putty (801) | Body Filler | AutoZone.com (http://www.autozone.com/autozone/accessories/3M-3-oz-Bondo-professional-glazing-and-spot-putty/_/N-25u5?itemIdentifier=540155_0_0_)

02-12-2012, 06:02 PM
did u repair the fiberglass with resin

02-12-2012, 06:03 PM
did u repair the fiberglass with resin

The cracks are not that big. i'm just trying to use the bondo to smoothen out the surface.

02-12-2012, 06:09 PM
you can apply filler over fiberglass/carbon with no problem, i do it all the time. your not giving it adequate time to dry or mixing it properly. general rule for me is to lay out the filler and put a line of hardener across it. so if the filler is a 3x5 area, then put 3-4" of hardener line on it. mix very well until there is no multiple colors, all a solid color. also where your doing the body work matters, if you're working in the cold air, you need a different hardener OR, a heat source to warm up the area/filler. if it's cold it could take an hour or more to dry. do not apply it after it starts to clump up/dry either.

02-12-2012, 06:14 PM
i think the problem may be that the dust from sanding was never removed, and the bondo wasnt even coming in contact with the bumper, give it a good wipe with a dry cloth then some compressed air before applying the bondo

02-12-2012, 06:27 PM
also on the fiberglass you need to make sure you get it completely sanded good, any shiny spots of paint and it will not stick.

02-12-2012, 06:34 PM
There is a lot of how to videos on youtube that showcase different products and how they work.

02-12-2012, 08:01 PM
youtube university of body repair :D

i've gone there to look up how to mix filler, hammer and dolly, almost everything

02-13-2012, 03:48 AM
Search on the tech forum ...... How to paint and body work .........to answer some of your questions. Body filler can go on plastic if it is prepped right, you can put body filler on almost anything

02-13-2012, 09:31 AM
First of all most of you guys don't know what you are talking about.
Second of all he does not have the right kind of 'bondo", he has air drying glazing putty that is used for pinholes on body filler after it's been sanded.
He needs to buy a quart or gallon of body filler (bondo for slang) depending on his need. But stating that his bumper is fiberglass he needs to use fiberglass to repair it, body filler will crack on fiberglass. If you have no idea what you are doing don't do it.

02-13-2012, 09:46 AM
Agreed, that glazing putty is not for filling cracks or anything..and your mixing hardener in with that putty? I'm highly confused.

02-13-2012, 06:45 PM
I've used filler to skim coat fiberglass several times with no cracks, just don't suck at it and it works fine. I really hope you're not referring to me not knowing what. I'm doing.

02-13-2012, 06:50 PM
thanks for help guys. i'll buy better bondo that i don't have to mix, next time around. :)

02-13-2012, 06:53 PM
you have to mix filler, it's the little tube of hardener that comes with it, otherwise it would harden if it were exposed to air. maybe get some kitty hair, REAL good stuff.