Plastic Bumper restore

[limenuke]

I have a bumper which has stone chips absolutely every where. They are right down to the primer (you can see bits of white behind each stone chip). I am fairly sure I don't want to skim coat everything with body filler so I started sanding it all down. This is my first time sanding plastic down. I've been using a 60 grit disc on my DA. I noticed that once I get down the plastic, the texture left behind on the plastic is that of like...a marred tire? It seems like the plastic is quite soft...the surface is not even at all. It does not sand as smoothly as, say, body filler.

That said, what is the best way to do this job? There are lots of little angles and lines along the bumper so I plan to hand sand it as well. My plan right now is to get rid of everything with the 60, hit it with the 100 and then the 150 and hope it turns out well. But because of the plastic's properties, I'm not sure if that's really the right way to do it. (It's an OEM BMW 3 Series bumper from the 1997).

I don't want to cause more damage if I can help it. There is no way around sanding right down the plastic - the stone chips are way too deep. But I'm thinking there might be a better way of doing it? Do it all by handing a block? Stop sanding and use aircraft remover?

Thanks in advance!

I took everyone's advice. Sanded with a finer grit. Prior to spraying adhesion promoter, I took a clean brush and tried to brush off as many plastic shavings as I could. There was tons and tons everywhere within the grains of the plastic. After this, I put thin layers of primer on until I built up a decent layer that I could sand smooth. Tack + solvent wipe, painted. Tack + solvent wipe, clear. It turned out just great.

However, upon installing, I realized something. I do believe I had this problem prior to taking the bumper off...it appears to be slightly bent. The bumper was involved in a collision at one point and it had cracked. I glued + puttied the crack so it's completely gone. However, the fitment of the bumper is not flush. One side of the bumper does not line up completely with the rest of the bumper. Specifically, the part of the bumper immediately in front of the wheel arch is bent too far out... No matter how I reposition the bumper, it will not fit flush. There is no part pushing it out.... Is there a way for me to "remould" the bumper with heat?

[Kalamity]

For plastic bumpers , sand it down with 180 grit on orbital sander, cause the 60 grit and so will make some ''hairs'' in the plastic, the covering with primer will be difficult. Whith the sander, it should take you around 3 hours to strip down the paint, change the paper when it clog, will need around 20 sheet of sand paper, if you have lots of paint, may take more...You can use sand blast for tne tricky areas, but low pressure.
you sand down the chips in plastic whith the 180, it will go down.
Then, wash it, prime it, sand down to paint, and voila!

[limenuke]

Right on! The paint on the bumper is OEM and really tough so I'm using the 60 grit to just break that down. Is it a good idea to just try to sand the "hairs" off with the 150 after that?

Also, did you say 20 sheets of paper hand sanding/block sanding?

[Kalamity]

it is not a good idea to use rough sand paper, you will work hard to fix the damaged plastic, and you should use an orbital sander, hand sanding will cost less paper, but will take you a week...
If you wanna go faster than fast, you will wreck your cover...
So: Orbital sander (with round 5 or 6 inch paper), grit 180 to strip, primer, grit 320 to sand primer, then a quick 500, and paint...
Use the right tool for the job, and it will be easy...

[TR3_Nut]

Hey guys
What about using the plastic bumper paint remover to strip?
I have same problem on Mercedes C230 bumper. Tons of chips and some damage from hugging a parking bumper.
Machine sanding all those contours seems difficult and maybe risky (in hands of a novice).
And no mention of adhesion promoter in repair recommendations? Is it not necessary if sanding is done?
Thanks- I really enjoy and benefit from this forum.
Pat

[limenuke]

TR3_Nut

You will definetely need adhesion promoter. If I didn't mention that - I certainly meant to.

I've no idea if bumper stripper works. I would hope it does but I've no idea how much of it you need and how much wiping you would need to do...

[Phil V]

I have a bumper which has stone chips absolutely every where. They are right down to the primer (you can see bits of white behind each stone chip). I am fairly sure I don't want to skim coat everything with body filler so I started sanding it all down. This is my first time sanding plastic down. I've been using a 60 grit disc on my DA. I noticed that once I get down the plastic, the texture left behind on the plastic is that of like...a marred tire? It seems like the plastic is quite soft...the surface is not even at all. It does not sand as smoothly as, say, body filler.

That said, what is the best way to do this job? There are lots of little angles and lines along the bumper so I plan to hand sand it as well. My plan right now is to get rid of everything with the 60, hit it with the 100 and then the 150 and hope it turns out well. But because of the plastic's properties, I'm not sure if that's really the right way to do it. (It's an OEM BMW 3 Series bumper from the 1997).

I don't want to cause more damage if I can help it. There is no way around sanding right down the plastic - the stone chips are way too deep. But I'm thinking there might be a better way of doing it? Do it all by handing a block? Stop sanding and use aircraft remover?

Thanks in advance!

What year and make of car are we talking about here ?

[another2centsworth]

What year and make of car are we talking about here ?

(It's an OEM BMW 3 Series bumper from the 1997).

[limenuke]

(It's an OEM BMW 3 Series bumper from the 1997).

Yup. You got it.

[Phil V]

Yup. You got it.

My cost on a NEW aftermarket front bumper for that car is around $75.00. For that kind of money I would throw away the old bumper and replace it with a new bumper.

[limenuke]

Really? I definetely cannot get my hands on something like that as an amateur. The aftermarket M3 bumpers go for 400 here in Canada from body shops...I doubt an aftermarket original bumper would cost 75 dollars here. I would definetely have gotten one if I could get it for that cheap.

I updated my post. Any ideas on how to reshape my bumper a bit? The plastic is a little bent...

[Bob K]

I’d recommend you listen to Phil, but he was a little off on the price. I looked in my CertiFit catalog and it shows $27.75 and they sell them to anyone that walks through the door. You may be able order one but then there is some freight. Give them a call (651) 765-4200 and see if this one fits your car BM3123C0. It says front (94-98 Sedan)(94-99 Coupe/Convertible/Hatchback, without Sport)

I got a cover for my Trailblazer a few months ago. It was almost free. I wouldn’t even put an ounce of Polyflex on my old cover after I saw what a new one cost. I got it home and found it was already primed and masked (two tone cover) amazing. Where are you in Canada?

Bob K

[Kalamity]

I’d recommend you listen to Phil, but he was a little off on the price. I looked in my CertiFit catalog and it shows $27.75 and they sell them to anyone that walks through the door. You may be able order one but then there is some freight. Give them a call (651) 765-4200 and see if this one fits your car BM3123C0. It says front (94-98 Sedan)(94-99 Coupe/Convertible/Hatchback, without Sport)

I got a cover for my Trailblazer a few months ago. It was almost free. I wouldn’t even put an ounce of Polyflex on my old cover after I saw what a new one cost. I got it home and found it was already primed and masked (two tone cover) amazing. Where are you in Canada?

Bob K

How's the fit?
The price is scary, but if it fit ok... why not?
In what town are they?

[Bob K]

The fit was excellent. My fog lamps mounted right in, and the lower air dam from the old bumper snapped right on. Nothing really wrong with my old bumper cover except it was scratched on both corners, kind of gouged into the plastic and for the low cost of the new cover I didn’t want to do the body work on the old one.

They are all over the country. Many of the large cities have a store. They aren’t the only company that sells after market though, but I wouldn’t hesitate using them. A few years ago someone brought me a bumper cover to paint and install and that was the first time I tried their product. The fit was great so I started going there.

Bob K

[Phil V]

I’d recommend you listen to Phil, but he was a little off on the price. I looked in my CertiFit catalog and it shows $27.75 and they sell them to anyone that walks through the door. You may be able order one but then there is some freight. Give them a call (651) 765-4200 and see if this one fits your car BM3123C0. It says front (94-98 Sedan)(94-99 Coupe/Convertible/Hatchback, without Sport)

I got a cover for my Trailblazer a few months ago. It was almost free. I wouldn’t even put an ounce of Polyflex on my old cover after I saw what a new one cost. I got it home and found it was already primed and masked (two tone cover) amazing. Where are you in Canada?

Bob K

I called Diehl autoparts out of Detroit for that front bumper (they get their aftermarket parts from Sherman and Associates out of Detroit also) . According to them the only '97 BMW 3 series front bumper they carry is for the 3 series sedan. And my shop cost on the bumper is $100 out the door.

How I came up with the $75 originally was I looked at a 3 year old Sherman and Assoc. aftermarket parts catalog that shows retail and wholesale prices. Wholesale price on that bumper was listed at $56.00 and retail was $100. I usually figure about half way between wholesale and retail for my cost which would have come out to around $75.00. Apparently the price has gone up from $75 to $100 in the last three years on that bumper just like everything else.