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Discussion Starter #1
I did a search and found quite a few old threads on this, so I thought I would post a new one. My 2007 350 has some front bumper damage - basically the air dam on the very bottom, barely visible, but still tore up enough for me to look into a repair. I was told by a local shop that advertises bumper repair that the plastics used on the 2007 is not weldable, so it's fiberglass patches, etc. The cost I was quoted was $450. So, any thoughts on this? Structurally, the bumper is sound. Not split through, not flapping - just a patch of ugly. Thanks in advance for your thoughts!
 

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Yes, fiberglass repair from the back. I don't know if $450 is a good or bad price since I repaired mine myself. Worked fine until my wife hit a cement parking stop. Had to replace the bumper.
 

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I did a search and found quite a few old threads on this, so I thought I would post a new one. My 2007 350 has some front bumper damage - basically the air dam on the very bottom, barely visible, but still tore up enough for me to look into a repair. I was told by a local shop that advertises bumper repair that the plastics used on the 2007 is not weldable, so it's fiberglass patches, etc. The cost I was quoted was $450. So, any thoughts on this? Structurally, the bumper is sound. Not split through, not flapping - just a patch of ugly. Thanks in advance for your thoughts!
I use a "staple" type repair tool just for rubberized bumpers. It works realy well. It is used on the back side of the bumper to hold the two sides of the crack together while the cosmetic repair including respray paint is done on the outside. Two links for a video explaining how it is done and then the tool I have and used several times. Good luck.


https://www.amazon.com/Astro-7600-Staple-Plastic-Repair/dp/B0096PGOOQ/ref=sr_1_sc_2?ie=UTF8&qid=1528288340&sr=8-2-spell&keywords=plastic+bumber+repair+staple+system
 

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It's a relatively simple fix that you can do yourself and save $450 by paying someone else.

The damaged portion is low enough on the bumper that you can get to it from the back side to easily make repairs without having to remove the bumper. There's nothing behind it to get in the way. (Ask me how I know.) An inexpensive fiber glass repair kit applied to the back side will do the job. Thoroughly clean the back side and scuff it up to give it some tooth. Use the jelly type of resin as opposed to the watery type because it will probably want to drip as you are applying it. Since you will be laying on your back while working, wear a shirt that's expendable or lay a towel on your torso for any unwanted drips. Jacking the front end up makes the job easy. Just be sure the two mating surfaces are aligned with one another while the resin is hardening. I was able to use a small spring type paper clip along the bottom edge for alignment. Once done, it is unnoticeable. No touch-up paint was necessary.
 

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When I took a close look at my lower bumper (repairing parking sensors) I noted a lot of crazing and cracking in the paint.


Took bumper off (for parking sensor replacement) and found several fibreglass patches and body filler repairs.


The fibre glass was not sticking to the plastic, and the original cracks were opening up again through the body filler.



The problem is fibreglass or body filler is not flexible enough for the bumper.


I used Isopon - Products which I reinforced with aluminium mesh.




This is a flexible filler/repair kit and has given excelent results, and the bumper remains fully flexible over the repair.
 

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Discussion Starter #7
Thanks everyone for the replies. I wasn't too keen on spending a lot on this, so you've given me some options to look into. Thanks again!
 

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After repair, what outside paint?

I use a "staple" type repair tool just for rubberized bumpers. It works realy well. It is used on the back side of the bumper to hold the two sides of the crack together while the cosmetic repair including respray paint is done on the outside. Two links for a video explaining how it is done and then the tool I have and used several times. Good luck.

https://www.youtube.com/watch?v=1VN6lxdC9LY

https://www.amazon.com/Astro-7600-Staple-Plastic-Repair/dp/B0096PGOOQ/ref=sr_1_sc_2?ie=UTF8&qid=1528288340&sr=8-2-spell&keywords=plastic+bumber+repair+staple+system
Great tool! My question — and I know nothing about the subject, except that when old, under-bumper cover cracks started to spread, I got paint pinch and flaking (see attached image), which means a complete repaint for the cosmetic outside portions, and, I hope, a thick, but flexible, “binding” coat over the repairs inside the bumper.

It’s obvious even to a dunderhead like me that both these paints must have a good amount of flexibility, but what paint, primer, and clearcoat should I use, especially on the cosmetic side, the color being 762, Tellurium Silver Metallic?

Thanks!

Bart
 

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I did a search and found quite a few old threads on this, so I thought I would post a new one. My 2007 350 has some front bumper damage - basically the air dam on the very bottom, barely visible, but still tore up enough for me to look into a repair. I was told by a local shop that advertises bumper repair that the plastics used on the 2007 is not weldable, so it's fiberglass patches, etc. The cost I was quoted was $450. So, any thoughts on this? Structurally, the bumper is sound. Not split through, not flapping - just a patch of ugly. Thanks in advance for your thoughts!
Have a look on Smooth-on website, they make a range of polyurethane resins that bond very well to the plastic bumper material, I do a little bit of casting and thought i would try it on a badly damaged Rocker panel, stuck insulating tape on the visible side to stop the resin running through then poured a little on the damaged area and kept moving the panel untill the resin set. Made a great repair and is flexible.
Regards Stuart
 

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If the base repair is done correctly, you will not get paint cracking...or any other paint defect.


If the base repair fails, then of course you will get paint issues showing.


All car paints are flexible enough for plastic body parts, but make sure you use a suitable primer for plastic, before the regulare primer, paint and clearcoat.


The primer in the isopon kit is perfect.
 

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I finally got a look at the “repair” inside my bumper.

If the base repair is done correctly, you will not get paint cracking...or any other paint defect.

If the base repair fails, then of course you will get paint issues showing.

All car paints are flexible enough for plastic body parts, but make sure you use a suitable primer for plastic, before the regulare primer, paint and clearcoat
My local took the bumper off today — there are two totally unsuccessful crack “repairs” that look like they were done by the Three Stooges on meth. The body shop owner was picking dime-sized chunks of Bondo (or maybe bubblegum) out of the FIRST NON-stabilized crack that was causing my paint to peel off, and the middle crack was split COMPLETELY THROUGH some flexible black epoxy garbage that was used for the SECOND “repair.” The only thing stopping the middle crack from going all the way through the bottom area of the bumper was the silver Gorilla duct tape I laid in with a brayer (a rubber-faced roller for spreading ink in hand printing). The Gorilla duct tape was literally the only thing holding the part of the lower bumper from the lowest point under the front end — where it was cracked all the way through for a distance of five linear inches — to the bottom of the air intake, which was within an inch and a half of splitting.

I can see why the clowns who sold this thing listed it on “Bring A Trailer,” where you almost never have a chance to REALLY check out a vehicle for such slapdash kludges, which NO number of “Bluebird of Happiness” Carfax vehicle reports is going to tell you about. What I still don’t understand is why I was stupid enough to buy it.

My body guy is going to reinforce the inside bottom of the bumper correctly, burr into the cracks, apply filler, and sand the rest of the bumper in preparation for Mercedes primer, Mercedes 762 Tellursilber (or Tellurium Silver, Iridium Silver, Diamond Silver — under which nomenclatures and more 762 Silver Metallic has been named by Mercedes), and then, Mercedes clear coat, all for less than $1000. Thank the gods that Mercedes long ago deleted this front bumper from its replacement parts inventory — I imagine it would have cost at least $3000, NOT counting primer, paint, and clear. (My guesstimate rule of thumb for any “Genuine Mercedes” replacement part is to look at what a similar part on a Lexus costs, then multiply by 3).

By next spring, I hope to have all the paint chips filled — miraculously for a 14-year-old car there are no dents or door dings — everything mechanical up to snake, the whole car ceramic coated (Armor Shield IX), and ready to sell.

I’d like to say it’s been fun, but it hasn’t. Mea maxima culpa.
 

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By next spring, I hope to have all the paint chips filled — miraculously for a 14-year-old car there are no dents or door dings — everything mechanical up to snake, the whole car ceramic coated (Armor Shield IX), and ready to sell.

I’d like to say it’s been fun, but it hasn’t. Mea maxima culpa.

you are going to make a nice car for someone else :grin:
 

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Update — if anybody cares — on my ‘05 SLK55 AMG bumper

My body shop has finally cleaned out all the shade-tree mechanics’ several attempts at trying to ensure the bumper wouldn’t split in three pieces, and he tells me the lowest level of the archaeological dig has found the first attempt at a fix — a completely exiguous layer of chicken wire (I’m not kidding) and Bondo. The body shop is cleaning out all the pitiful effects of home-made “fixes,” then he’s going to plastic staple the two big cracks closed, then fill and sand with proper materials, preparatory to primer, color-coat (M-B code 762), and clear coat. I’ll be shocked if it matches the original color of the rest of the car. Maybe I’ll paint some flames and Von Dutch-style pin-striping on the bumper...

Bart
 
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