Porker928

Thanks for your replies but I think I agree with 'sharknoob'.

The only logical explanation for the plastic not moving back to its original position is because its being held there by the, now bent, metal strip that runs across the top.



Considering the number of 928's that break down and have to be pushed I'm surprised this problem doesn’t come up more often.

I'll have a go fixing this and report back at a later date.

Ben
1984 S2 Manual

sharknoob

Strip #20 pops off with a couple screws ...The bent lip I was thinking of is under the cover that those screws go into

Take your time with it if it is bent it will affect the body line between the lid and cover

Mrmerlin

Without a picture its hard to tell what is not in the correct position.
That said the only moving part of the rear bumper assembly is the shocks.
Note on the EU cars the shocks may also be replaced/refitted with collapsible stand offs ( think similar to a thin metal soda can)
These will also crush and then the rear PU will be crushed till they are replaced.
The part you have pictured ( 19 ) wont bend unless the rear end has seen substantial crash damage. This part is actually screwed into the the rear chassis and captures the PU , Its not going to bend.
Since you note a deformation I would suggest that you look under the rear PU and see why its deformed, pay close attention to the bumper PN 1 in the picture and how its connected to the chassis,

If you have the shocks then you may be able to insert the jack and jack the bumper out again, if you have the crushable cans then the bumper will have to be taken apart to replace them ( the shocks should also be replaced as they are one time use)

sharknoob

True pictures would be great .... I picture two hand prints right above the Porsche letters
You should be able to run your finger between the lid and the cover to rule that out if you can't see it

hans14914

I remember years ago when I first started looking at rennlist, that there was a procedure to straiten the bumpers using a hot-tub. I guess leaving the bumpers in the water helped reset the memory of the plastic without any deformation. Cant say I have seen it mentioned in several years though.

Porker928

Stranger and stranger.

I have removed the metal strip that runs across the top and now the bodywork is free to move in that area but still hasn’t returned to its normal shape.

Could the plastic have decayed somehow and lost its flexibility?

I’m thinking I may have to employ the ‘Hot-tub’ method of repair.

How easy is it to remove the whole bumper cover?

Mrmerlin

from the looks of things you may have damaged the rear bumper supports/shocks/cans.
I would say that removing the rear bumper would be a good idea at this point to evaluate the underneath parts.
There about 5 small 8mm nuts on each inner fender, spray with penetrant oil then scrub the bolts with a tooth brush or wire brush first so they dont snap off.
Remove these then, if you have bumperetts remove them.
Then lay a big blanket on the ground under the bumper .
remove the center strip and pull the PU cover out about 2 inches so you fit your hand in from the top and remove the grommet that is pressed into the rear bulkhead with the wire harness the light connector will then come through disconnect this as well the tag light connector and the do the other rear light the same way. pull the PU off the car and lay it on the blanket.
Please take pictures of the underneath portion and post

heinrich

That's got nothing to do with metal. Park the car in the sun. Ow wait you're in the UK ... use a heat lamp.

G Man

park that thing in the sun to warm up and try using a toilet plunger to pull it out with. I have had success with the plunger on large pushed in areas on a truck bed panel. Get the plunger wet first to help with the suction seal.

M. Requin

Jim and that Gorilla are right, I think - that's a pop-in. To pop out , as they said, park it in the sun, and then you may need to take a blunt instrument to help it remember it is supposed to be convex, not concave, but I'll bet a beer that's all it is. A caveat, of course - if this happened before and the bumper shocks were trashed, Mr Merlin may have the answer, but just pushing one as you described won't result in that kind of damage (I think).

mark kibort

heat gun and go pro camera suction cup.

I got TAGGED at a race a couple of years ago. it was pushed in about a foot!
heat gun popped it out and you can barely tell i was ever hit.

Porker928

Unfortunately I have failed to correct this problem.

And believe me - I've tried everything.

I am now going to replace the rear bumper cover with a re-painted second hand one.

So my next question is this. >

When I get another bumper cover can I strip it with standard dichloromethane / methanol striper without damaging the plastic ??

Thanks.

DanielD

Boy Howdy!

86'928S MeteorGrey

There are threads regarding refinishing the polyprolelene bumper covers you can search for. IIRC, the best way is to use walnut media in a sandblaster and remove all of the paint down to the plastic. Then use a primer that is specially formulated for flexible/plastic body panels. Next use paint that is compatible with the primer!

Kevin Michael

Hey Hans! I can think of better things to get into a hot tub with than a bumper cover! BTW Thanks for the cover you sent for Paul's car. It is in primer now and looks great.
Kevin