Help with my bumper

[Brian]

I have some spare parts for my 1988 buick reatta but they are a different color from my white reatta. How do i go about prepping and painting the spare bumper please help! :huh:

[Ronnie]

Welcome to the forum Brian! I'm not a body man so I can't help much with your paint questions.

 

I've read that the shiny part of the the bumper is made of aluminum that can be polished and clear coated. I think it was originally anodized at the factory instead of polished but I'm not sure about that.

[Brian]

okay, Is there something on this site I can go too and maybe ask on there? Its looks like the whole back bumper is plastic which is what I want to paint white

[kdirk]

The bumper impact bar (only the top surface is visible when the bumper is fully assembled with all trim) is anodized aluminum, unless it was previously painted for some reason. I have seen a few cars done this way but it isn't common, and isn't factory original. With that out of the way, there are multiple components involved in both the front and rear bumpers. There is a plastic bumper skin, painted vehicle color, attached to the impact bar (aluminum part) with a bunch of plastic push rivets. Then there is a rub strip (may be either black or body color depending on how car was optioned or subsequently repainted), attached with self-tapping nuts over plastic pegs molded into the rub strip from inside the impact bar.

 

On the rear bumper, there are two bump guards near the center under the license plate, these are mounted with machine nuts on integral threaded studs. There is also a lower valance painted black that has a notch for the exhaust. This is attached with several screws and some brackets at the outside ends. On the front bumper, the setup is essentially the same without the bump guards. Your car may be equipped with a front plate holder, if so it is screwed directly into the rub strip at the top, and into two metal angle brackets at the bottom.

 

Disassembly of either bumper is time consuming, as the bumpers need to be removed from the car to remove the rub strips and plastic skins from the aluminum portion. Getting the plastic push rivets out of the bumper skin is also a real job as there are so many of them. Patience is the key factory here, along with good tools and a padded surface to set the bumper assembly on while working on it to prevent scratches or other damage.

 

Once disassembled, prep, priming and painting is done by standard procedure for flexible plastic body panels. A good urethane paint with flex additive is heavily recommended to prevent spider webbing cracks from forming in the paint if these piece are flexed at all. A heat gun can be used to smooth out small dimples that may have formed in the plastic pieces - particularly the rubs strips - as the plastic has a memory and will return to original shape when reheated. As with all auto paint, good prep and good product is everything. Poor prep or cheap paint will render a sub-standard finish. One stage paint is not suggested.

 

Kevin

[Ronnie]

Kevin, With your permission I would like to use the information you posted above about the bumpers in the How-to section of ROJ to give Reatta owners a basic understanding of how the bumper parts are assembled. Although it wouldn't be a step by step guide to disassembly of the bumpers, I think that information is too useful to allow it to get lost here in the forum.

[kdirk]

Ronnie, please feel free to use it. The first time I removed bumpers from a Reatta I was discouraged by how much disassembly was involved. This setup looks nice on the car, but is a real dog to take apart for repainting, or polishing the aluminum. Getting the plastic rivets out is the worst part, they are difficult to remove without damaging them, and I've not found a really good technique for this. I use various small tools (jewler screwdrivers, small pin punches, mini long nose pliers primarily) but they still aren't easy to get out. I'm of the opinion that GM probably intended these fasteners to be disposable, with new ones being used after a repair or repaint of the bumper skin. It just makes a lot of extra work to try and save them for reuse.

 

Another note is that the rub strips tend to dimple where the mounting posts are molded into the back side. Once the self-tapping nuts have been installed, they pull inward on the strip, and given the soft nature of the plastic, it deforms easily at the mount points, especially those on the corners where the bumper curves around. One needs to be careful not to over tighten and make this dimpling effect worse. As posted previously, once removed a heat gun will smooth it out again, but there is a certain technique to it and it's not so hard to scorch the plastic if you aren't careful not to over do it.

[Ronnie]

Thanks Kevin. What I post in the How-to section won't be written verbatim but will will include as much of the information you have posted to the forum as possible. I will let you know when I have it finished for your review. Then we can modify it if needed.

[rogold]

I am also working on replacing the metal part of my front bumper because of a small dent on the nose. I got a junkyard bumper assembly in nice shape, just the wrong color.

  Stripping the driving lights, grille, and mounts went fairly quickly. The speed nuts holding the rub strip came off well after spraying with WD40, didn't break off any plastic studs.

   I also had trouble with the plastic rivets at first. But figured out if I sprayed them with the WD40 on the backside of the bumper, then, again from the backside of the bumper, I inserted a short tiny screwdriver thru the legs of the rivet. Then holding the screwdriver on both ends just push the center shaft of the rivet thru, and they popped out far enough to easily pull out from the bumper face.

   I has to rotate some of the rivets by hand to make working inside the gap on the backside of the bumper easier.

   A nail or similar tool would probably also work too, but the handle on the tiny screwdriver gave me something to grip.

   Now that I have just the bare metal left, next job will be polishing the metal. Just waiting for some warm weather outside to do it.

[Ronnie]

Kevin, I have added your information from your previous two post to the ROJ How-to guides. I've changed the wording slightly and rearranged paragraphs slightly to fit in as much info as possible from both posts.

 

Bumper Components & Disassembly

 

If you see anything that needs to be changed (including the title), or you have anything that you would like to add, just let me know and I will be happy to make the changes.

[kdirk]

Ronnie,

 

That looks fine, though I note a spelling error carried over from my original post. Where it states "patience is a key factory..." Obviously should read "factor", not factory. Thanks for reading it for inclusion as a quasi-tutorioal.

 

KD

[Ronnie]

Kevin, Spelling error corrected. If you find anything else that needs changing let me know. Thank you for this and all the other articles you have contributed to ROJ.

[ReattaMondatta]

My bumper impact bar was badly scratched, so I decided to paint it black. I removed/disassembled the entire rear bumper assembly without breaking anything (yay!) but the rub strip self-tapping flange-nuts were very rusted and I do not want to re-use them. Does anyone know the specs on these? I took one of the rusted ones to a hardware store and the closest fit was a coarse 1/4" thread, but it was a little loose.

 

Incidentally, its a miracle my bump guards didn't break. Seems like some kind of thread lock must have been used on them. I had to get them off with a breaker bar. They thread normally now after working them through with some Blaster. You know, just enough to fall off in a few years.

[jon L]

Ronnie, If you polish the bumpers to shiny, you cannot clear coat them.

Let me clarify that. If you do clear coat them it will not stick.