[Greg Reid]

It took me probably 10 coats of epoxy, each mostly sanded away, to fill those tiny hairline cracks. That, combined with the 3m bumper repair got them filled. My wife thought I was crazy because I was sanding and painting that bumper every other day for two or three weeks..

[PaulatFast]

Originally Posted by 68ragtop

... I am guessing when you put your first coats of epoxy primer on, your hoping to see no missed cracks, just possible sanding marks from the repairs.

YES! Very well said!

[68ragtop]

Finally getting to the bumper after sand blasting it a few weeks back. First off, that 3M epoxy is incredible. I have never used that same product before. Bonds to the endura like it was made for it. I have filled in the damaged areas & v-'d the cracks that I can open with my finger nail. All the other cracks I mentioned above, really don't seem like cracks. I can feel them with my finger nail & I can see them, but they do no open up at all & are just a few mils deep.

This bumper had original paint on it & that paint was cracked everywhere. It almost seems as if these marks are from the environment get through the cracks in the paint over decades of time. It really doesn't seem practical to v-all of these out, they are literally everywhere & there would be nothing left to the bumpers original surface. I am guessing these are the marks that are usually filled with the sprayed epoxy coats, but how about filling them with the 3M filler & the epoxy spray.

Here's a picture of what I am talking about.

[salem1912]

I left a lite skim coat of the 3M epoxy on the entire bumper. Your right the stuff is great to work with. Very happy with the results. BTW only V the very deep cracks.

[68ragtop]

That looks extremely nice!

I had a few small gauges I filled & sanded. Then the dust from sanding the 3M epoxy seemed to cling to the hairline cracks in the raw endura when I rubbed over it. I then took a flat blade screwdriver, put a little pressure against the endura & passed over the cracks. The cracks that opened up I Vee'd out & still have more to do. There are more of them than I initially thought. the small ones, like in the picture I posted above. Really don't open up, but they are there. My thought is to press the 3M epoxy into those. without v'ing them out.

Not trying to cut corners here, but if you look at the photo, you can see where there is just a crazy amount of these small marks. If I vee's all of those out too, there would be no surface left to the bumper.

[Greg Reid]

I didn't vee anything out that looked like that. I used a combination of a skim coats of the 3m and multiple coats of epoxy. Epoxy and sand over and over. The epoxy will eventually fill those imperfections.

[Formula8]

Originally Posted by Greg Reid

I didn't vee anything out that looked like that. I used a combination of a skim coats of the 3m and multiple coats of epoxy. Epoxy and sand over and over. The epoxy will eventually fill those imperfections.

I used the same technique. However, instead of SPI's epoxy, I used 3m's flexible primer which is water thin so it took what seemed like 7-8 coats. It's been 2 years now and so far, so good.

[68ragtop]

So, here's where I am at: I have all of the cracks grooved out & repaired. Now these are the larger cracks that I could open up using a little pressure & a straight edge tool. Everything else, that looked like a crack, but just had no depth to it (wouldn't open up) I left there.

Then like Tom did, I decided to skim over the whole bumper with the 3M. Not thick! Just into the surface, I am now sanding it all back off with 220 & basically the only epoxy that is staying on the surface is what has filled those really small marks/cracks & its also filling some of the rough, raw surface of the endura. This is turning out to be a tedious & time consuming repair. But this last step, should cut down on filling these imperfections with primer. Either way i go, I am still sanding



BTW, I stuck a small blob (1/2 circle) of the 3M epoxy on the surface of the endura to see if I could pop it off when it fully cured. No-way, I pried at it with a screwdriver & it would not lift, even seemed as if I was going to damaged the endura trying. This made me feel confident in the stuff. I know this is stuff paulatfast already knows, but it still helps my brain.

Anybody know if the 3M epoxy can be wet sanded? I am thinking that would help me differentiate whats epoxy & whats endura. As it dusts up, its hard to tell.

[Greg Reid]

I wet sanded mine with no problems...and yes, it's tedious. You basically have to do the same job over and over until you're satisfied with the finish.

[68ragtop]

I guess thats why I decided to fill the imperfections with the 3M epoxy instead of epoxy primer. It adheres like crazy to the endura, it's flexible, & will fill the imperfections quicker than the primer. I feel I am still sticking to what paul has stated works on these bumpers, just using more 3M epoxy & sanding more on the front side & less epoxy primer on the backside. (hopefully) I did order the SPI epoxy primer, I found a NAPA distributer that ships about 100 miles from me.

Greg, did you wet sand the 3M epoxy, or the epoxy primer? I am looking to wet sand the 3M epoxy, only because it will be easier to see what I am doing.

[Cammer-6]

I do very little sanding by hand,when a machine will do it,so dont know whats up with not knowing where to sand.180-220 on a DA will do a fine job for knocking it down.

[Greg Reid]

I wetsanded the epoxy. I really don't recall whether I ever did it with the filler..I think it was because I always used another coat of epoxy shortly after sanding the filler and I wanted it completely dry.
I can't imagine you'd have a problem with wetsanding it though as long as it's fully cured.

I do 90% of my sanding by hand.....I seem to think I can feel the contours better. On the endura, I also worry about rounding the edges off. I want them sharp. In fact, on the endura, I sometimes didn't even use a block, just my fingers. This would have been on those narrow, interior contours.

[68ragtop]

Originally Posted by Greg Reid

I wetsanded the epoxy. I really don't recall whether I ever did it with the filler..I think it was because I always used another coat of epoxy shortly after sanding the filler and I wanted it completely dry.

Thanks, This will be my first experience with SPI epoxy primer, so it will be interesting to see if it sands as easy as others have said. I have only used PPG DP series. fantastic product, but that stuff sands very poorly & clogs up the paper. I'm just sanding the 3M dry & blowing it off with the air chuck often. Its working fine. But you bring up a good point, for how porous that endra is, its not worth risking getting moisture trapped.

[68ragtop]

Thought I would post on my progress.

As I posted above, I repaired all the cracks I could find, I then skimed over the whole bumper with the 3M two part epoxy. This was a very tedious step. I took the time to block sand almost all of the 3M product back off, only leaving material in the low areas, crazing cracks & other imperfections that I could not see with my eyes.

I then sprayed two coats of the SPI epoxy & the earlier work on the last stage paid off.
There are no marks anywhere on the bumper, just a few imperfections I missed durring the previous step. From what I see, I think one sanding of the primer & I might be done. The 3M material sands very easy were the endura does not, so I had to be careful not to oversand as I hit the endura surface. This is why a D/A would never have worked for me.

The SPI epoxy is really different from what I am used to using. Not in a bad way, just different. What I really, really like is it sprays nice. I used a devilbiss plus gun, & installed a GTI air cap with a 1.5 tip. Best spraying primer I have ever shot, almost like glass when its wet. What was weird, was as the primer sat in the mixing cup durring its induction time, some of the components pooled on the top of the cup. Simular to how metalic paints do. It also drys fairly glossy, & feels almost rubbery to the touch. Again, nothing wrong with that, just very different. I will probably put on a guide coat & sand it on Friday.

[Kokamo]

Looking good. Going to take the exact same steps on my 69 endura here in a week or so.

Good job sir,

~Joe

[70oldgoat]

"..the 3M two part epoxy..."

My first attempt at restoring the 70 GTO front bumper.

Will someone provide the 3M product number for the two part epoxy you guys are using?

I was unable to find 3M product number 05900 on the internet which leads me to believe 3M may currently be using a different product number.

Many thanks for the information in this string and the lead to the website: http://www.goatsgarage.com/bumpfrm1.html

[68ragtop]

I used 3M #05895 as recommended by Paul. Works fantastic.

[70oldgoat]

Thanks for the quick reply...I look forward to trying it out.

[grandville455]

Subscribed

[68ragtop]

Wow, Hard to believe this thread is over 6 years old!

I painted my car (and Bumper) about 2.5 years ago, no cracks or shrink marks in the endura at all. Still looks perfect. However, my car is still in the assembly stage, so it hasn't seen any weather, & very little sunshine in a climate controlled environment.

Granville455, I buy My epoxy primers from Scott at NAPA in Chippewa falls. Great Guy