Rear bump stops series 4 spider - Alfa Romeo Forum
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(Post Link) post #1 of 11 Old 16-06-09 Thread Starter
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Cry Like A Baby Rear bump stops series 4 spider

I'm currently rebushing the rear end of my series 4 spider and thought I would start with,what I thought was ,the easiest job first,the rear bump stops.

After wrestling with the posidrive screws which wouldn't budge,I ended up drilling out the counter sunk heads which hold the bumpstop plate to the bodywork,so far so good.

But the bolts I think, have corroded to the aluminium spacer and no amount of heat,hammering or swearing will remove them,the aluminium spacer is fused to the bolts.

Help,what can I do now?Grinding the aluminium spacers off,rendering them scrap is something I don't want to do.

Surely this must be a common problem,has anybone else encountered this problem and what did you do to fix it?
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Not sure what you mean by 'rear bump stops' - I have alot of aluiminium parts which "corrode" when fitted against other metals on the boats i work on. RIWAX anti corrosion spray and any liquid soap. Spray alot on and cover in squeezy soap, then go at the parts with a nylon string (something that won't break easily - you have any old fishing rods ?) and act as if you were using the string like a saw all round. You sometimes have to leave the muck to work itsself right in over night. You'd be surprised at how easy it is to part the pieces afterwards.
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(Post Link) post #3 of 11 Old 16-06-09 Thread Starter
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Hi Alfa Black,the rear bump stops are above the rear axle but screwed to the body with two long cross headed screws,these screws/bolts go through the bump stop plate,through an aluminium spacer and are threaded into the bodyshell.

The bump stops themselves are rubber mouldings bonded onto a plate which prevents the rear axle clashing with the bodyshell when the suspension is fully compressed.On my car the rubber mouldings have gone altogether leaving just the steel base plate.

The steel bolts have reacted with the aluminium spacers(which are about an inch thick)and I can't access the bolts.
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If you hadn't already drilled the heads off I would have said use an impact driver or use a screwdriver that you can turn with a spanner and use your car jack to jam the screwdriver up against the screwhead with the whole weight of the car on it. A good soaking with a penetrating liquid would also help.

Alternatively, you could stiffen the suspension enough so that you never have to worry about it hitting the bumpstops
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There is an alternative.
The rubber bump stop is only there to take out the impact should the axel rise up to high and stop metal to metal impact.
Many years ago on one of my 105 cars I had the same trouble so I cleaned, degreased and lightly sanded the plate, then used some D shaped rubber (which happened to be the type that went round a boat, Alfa Black).
I cut to length and glued on with 2 part epoxy glue.

Had the car for several years, they never came off and never failed an MOT.
Just thinking outside the box
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Can you not get a drill up there and carefully drill out what's left of the bolts? If you drill them out enough using a larger and larger sized drill-bit, they usually weaken and fall apart.
Or just glue new rubber stops on top of the old plate with an epoxy, like araldite? That would be the easiest, unless you wanted to replace the check straps, then you will have to solve the problem! They don't do anything up there, just wait their whole life to get a whack when the springs are weak, and the rear bottoms out!
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(Post Link) post #7 of 11 Old 17-06-09 Thread Starter
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Idea

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Originally Posted by spiderserie4 View Post
Can you not get a drill up there and carefully drill out what's left of the bolts? If you drill them out enough using a larger and larger sized drill-bit, they usually weaken and fall apart.
Or just glue new rubber stops on top of the old plate with an epoxy, like araldite? That would be the easiest, unless you wanted to replace the check straps, then you will have to solve the problem! They don't do anything up there, just wait their whole life to get a whack when the springs are weak, and the rear bottoms out!
I did think of that,but you can't get square/vertical onto the existing bolts with a drill because of the axle,but I've just had a brainwave,if I bore an 8mm hole through the side of the aluminium spacer block,exactly where the bolts are, at 90 degrees to them,that should hopefully cut through the bolt,releasing the aluminium block,but not destroying it and hopefully leaving enough of the bolts to release them from the bodyshell with mole grips.

Once the aluminium spacers are removed from the car I can put them in a pillar drill and bore out the remains of the old bolts

I can get good access from inside the wheel arch,I shall report back later with results

On one of my favourite driving roads,there are a lot of undulations and the axle would strike the bodyshell with a sickening metal to metal crash everytime.
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(Post Link) post #8 of 11 Old 17-06-09 Thread Starter
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Success!Well,yes and .......no

Boring the 9mm holes through the side of the spacer block worked perfectly,cutting through the bolt and with a screwdriver,I managed to prize the blocks away from the bodyshell.

It even left around three quarters of an inch of the threads of the old bolt projecting from the bodyshell,even better I thought I would thread on two M8 nuts and lock them together and unsrew whats left of the bolts from the bodyshell

DISASTER!What was left of the bolts sheared of flush in the mountings in the bodyshell

Please don't say I have to bore out and re-tap the mountings in the bodyshell

This is just one side,I've still the other side to do
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well you are nearly there (one side at least!)...if you can now get a drill verticle to the sheared off bolt (whether one of those flexible drill extensions might work here?), you could drill it out carefully through the centre again with a bigger and bigger drill, until the walls of the bolt are so thin, you can get the rest of the "bolt"-grooves out of the thread with a screwdriver, thus saving a re-tap?, then clean the grooves up with a tap and die. Or, drill through the centre of the bolt and put a hardened steel reverse tap into it and screw the sheared off remainder out that way? You can get hold the aluminium blocks new if you do have to destroy them, or just have them fabricated, shouldn't cost anything really.
If you are successful then put in the new bolts (preferably stainless!!) in with grease, waxoyl, anything at hand to make the removal job easier 10 years down the road!...in case.
Keep us informed how it goes, the other side ought to be easier, now you know what is ahead of you!
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This is coming too late for the side you're working on but for the other side, a rust penetrant spray can ease things along. There is a small cavity on the chassis side just above the bump stop where the screw threads are. Spraying in this cavity, perhaps every day for a week, can do wonders.

The main question though is why do the bump stops need replacing. Dampers/springs need replacing perhaps? Too much weight in the boot? Reason I ask is that I work on 40 year old 105s all the time that still have the original, good condition bump stops.

Jim
68 Mk1 Italian delivery
71 Mk2 US delivery
89 Spider Veloce
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(Post Link) post #11 of 11 Old 20-06-09 Thread Starter
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Hi Papajam,
I'm not sure why the bumpstops need replacing,I only bought the car last year and noticed that the rubber mouldings had lost adhesion and seperated from the baseplates.

The trailing arm bushes were gone and there was a heck of a lot of endfloat in the T-bar bushes so I just decided to re-do the whole back end.

Now that I've dismantled the back end of the car I'm looking at new dampers but I'm not sure which ones to get,Koni reds or eb spares bilsteins
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