The bumper sags so I took a look and the aluminum rail inside the bumper has so much corrosion that the bracket off the shock absorber pulled free.

I heard this was a common problem with Volvo and Mercedes, that due to the dissimilar metals the aluminum oxidizes and falls apart. It was suggested to clean both surfaces and buy a tub of some structural epoxy; brace it and let it set up. Any ideas or suggestions on what product to buy, or another solution for the problem?
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I'm stuck on Volvo and Volvo's stuck on me....

I have used this method on several bricks.
Remove the old bolts with the help of a wire brush and some "PB blaster".
Get new longer bolts( I use carriage bolts because they have a flush head and thus interfere less with the plastic bumper cover.(you will have trouble trying to find"grade 8" carriage bolts so don't even worry about that,the common grade 6 will be far better than whats been holding it on for the last several years)
Use very large washers on both sides of bumper and double nuts on the backside.
Expect to spend about three bucks in hardware and a couple of hours labor.
I would be interested in what type of structural epoxy would be used with the epoxy method?
thanks,good luck

You mean drill through the outside of the bumper and run the bolt all the way through? The carriage bolt smooth head, along with the washer, would appear on the outside surface of the bumper..
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I'm stuck on Volvo and Volvo's stuck on me....

no remove the plastic cover first then bolt the bumper core at the mounting points,then put the cover back on.the outer appearance should look original.

maybe that the 900 is not mounted the same as the 240 but the idea of replacing the bolts along with large washers to to cover the rotted out holes should remount the bumper in an aesthetically pleasing manner.

Has anyone done this yet on a 900?
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I'm stuck on Volvo and Volvo's stuck on me....

If you want to stop the corrosion you gotta insulate the aluminum from the steel. (Including the bolts and washers).
If you don't, it will continue to corrode.
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George Downs, Bartlesville, Heart of the USA!

Dear George,

Good p.m. and may this find You well. You're 100% right about isolating the aluminum from the steel. A way to do this: use plumber's pipe joint compound for gas pipes. It is gray and is teflon-free.

Use plenty of compound. Coat the underside of the bolt head, any washers that touch the aluminum, the bolt shank, and the underside of the nut (if it touches aluminum). Wipe away any excess compound, that oozes out.

Even a film of pipe joint compound will separate the two metals and prevent corrosion. Pipe joint compound does this (as well as seals the threads, to prevent leaks).

Hope this helps.

Yours faithfully,

Spook

I would not count on the pipe joint compound if the bolts were really tight because it does extrude out
and one tiny point of contact is all you need to complete the galvanic (battery) circuit.
If I did use pipe joint compound I would certainly test with an ohmmeter. Should show
infinite resistance (although because of capacitative effects it may start low and gradually
increase to infinity as the capacitor charges).

The connection through the distributor wall for the wire that connects it to the coil is a
good example of how such a joint should be insulated, although on a much smaller scale.
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George Downs, Bartlesville, Heart of the USA!

If you are in a damp or damp/salty environment this can be a severe problem.
Part of the cure is to make sure that the two metals are electrically insulated
from each other - well enough that an ohmmeter shows way up in the megohms or infinite resistance between them. Rubber or plastic gaskets between them (and around and under bolts and nuts) will accomplish this. It will be kind of a pain in the backside to do this but it will help arrest the corrosion and keep it from getting worse.

We had a maintenance crew attach a sign to an aluminum fence at the Fort Sherman (Toro Point) Breakwater with monel wire. The aluminum wire corroded through and the sign (and part of the fence) was on the ground in less than two weeks. It was pretty expensive to repair, made MUCH worse by the crew using carbon steel at first. Finally had to replace the whole fence.
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George Downs, Bartlesville, Heart of the USA!

Michigan! Lots of salt and 358,000 wonderful miles.
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I'm stuck on Volvo and Volvo's stuck on me....

Wow, I'm only 1/2 of the way through the life of my 940 (173,000 miles). I'm curious what major repairs you've had to do in 350,000 miles.

Eventually certain parts reach the end of their service life..but you are a long way off. The motor and the trans are bullet-proof. Make sure you flush your brake lines. The problem is that as the car ages you are less willing to spend money on it. But the motor goes on and on.......

Don't get behind on maintenance.
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I'm stuck on Volvo and Volvo's stuck on me....