RWD - remanufactured rear caliper pistons not to spec - is there a hack?

Volvo RWD 200 Forum

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remanufactured rear caliper pistons not to spec - is there a hack? 200 1988

a) A proper expanding threaded block with inside jaws to grab the rough inside of the piston is obviously the proper tool for the job. They're not grossly expensive, but I hear you about trying it some other way. There's also a threaded block shaped disk piston tool that is meant for aligning and inserting pistons. They can be relatively inexpensive, like $10-$15. I haven't used one so I can't attest to how well they might work for changing piston orientation and fitting into Volvo calipers, especially the rears.

b) You spent good money on these reman calipers. Is there not some way you can return them in exchange for properly oriented rebuilds? The minute you goof with them you risk damage and a voided warranty. If nothing else, you are owed at least a partial refund. This is by far the best approach to protect your investment.

c) Attempt to turn the pistons using something else wedged into the recess. Brake fluid from behind and in front for lubrication is generally required to make this doable. Try wedging in various sharp edged tools, my favourite is the single jaw of a large slip joint plier. No matter what, you must not scratch or damage the outer surface sides of the piston and do try to avoid significant damage to the piston face contact edge.

d) Pop the pistons out all the way past the seals with compressed air and re-insert them in the proper orientation using something like a centred C-clamp and plenty of lubrication (brake fluid). In experienced hands this isn't that hard to do, but you do risk tearing the seals if you can't keep the piston centred and perpendicular. If you've never done this before, I wouldn't be practicing on brand new calipers.

e) I am not at all recommending this for new calipers, but would certainly attempt it as a last resort on old calipers and have done so in the past for minor adjustment. Extend the pistons as far as you can then grab the piston outer surfaces with a non-marring grip, like the padded jaws of a carepenter's F-clamp or a C-clamp or welder's Vice-Grips with the piston well wrapped in protective tape. When extending the pistons, you don't want to break the seal if you can help it, which generally requires mounting them on the car and sticking something like the backing plate of an old disk pad, or equivalent thickness, in as a spacer then using compressed air to blow the pistons out against them, then removing the calipers to play with them on the bench. You will also need to carefully pop out the dust seals for access, just don't accidentally puncture them, which is so easy to do if you slip.

f) If you can't/won't return them, then maybe try living with them the way they are before inadvertantly damaging them. I wouldn't mind betting the anti-squeal properties of the stepped design are not grossly affected by the pistons being 180 deg out of proper orientation. In case you haven't noticed, lightly applied brakes can squeal plenty in the reverse or the forward direction.
Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now


New need insight into rear caliper replacement - tool clearance [200][1988]
posted by  tbb2  on Wed Apr 3 12:04 CST 2019 >

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