1991 740 front brake seized

nisan17 · Post by **nisan17** » 29 Jul 2010, 14:24

Hi Group,

I believe my front brake caliper(driver's side)is seizing. It must be releasing somewhat as I can still rotate the tire/wheel with some resistance. Is there a spray I can apply to loosen up the piston? Or should I replace the caliper or rebuild?

Thanks in advance,

Post by **billofdurham** » 29 Jul 2010, 15:26

Unfortunately there are only two options.Rebuild the calliper with new seals or replace with a rebuilt calliper. Rust inside the calliper causes the seizure.Brake fluid absorbs moisture and holds it (for a while)then it makes it's way to the lowest point in the brake system(the callipers or wheel cylinders).This is why it's critical to flush the brake fluid regularly. It is also possible that the dust cover has torn allowing water into the calliper from the outside.

If it is possible to clean off the build up of crud on the piston with brake cleaner then it is possible to rebuild the calliper. If the piston is badly corroded do not use abrasives to get the rust off. It is beyond hope and must be scrapped.

Bill.

nisan17 · Post by **nisan17** » 29 Jul 2010, 15:41

Thanks so much Bill. Another reason why this is not my career!!!

Retired MVS Contributor · Post by **Retired MVS Contributor** » 29 Jul 2010, 15:58

There is another possibility...The front calipers are sliding calipers with rubber boots on the slides...When the boots get torn for some reason (age, etc) the sliding pins rust and stick...They can be cleaned up if that is the case, but if the boots are not replaced they will rust up again...

Volvofix1 · Post by **Volvofix1** » 13 Aug 2010, 15:19

The best bet for you is to get 2 rebuilt calipers and 2 brake hoses ,bleed the brakes and it will be fine .Don't buy just one caliper

Dick K. from Fla.

Retired MVS Contributor · Post by **Retired MVS Contributor** » 13 Aug 2010, 15:42

It is not usually the caliper, it is usually the caliper retaining pins...This car has what are called "sliding calipers" and the pins that the caliper slides on rust up...There are rubber boots at this point that keep the pins clean and they deteriorate...The pins can be removed, cleaned up, lubricated, and the boots replaced...This caliper has pistons on only one side of the disc and when pressure is applied the caliper slides on the pins, pinching the disc betwwen the pads...Check the pins before you order a caliper...

rob2volvos · Post by **rob2volvos** » 14 Aug 2010, 19:32

Funny this should be reported now. I have a 1992 740 whose brakes were performing poorly. I removed the wheel and the caliper on the drivers side. I hung up the caliper on the suspension spring. Then I removed the bracket (what's the name for this item?) which is held in by 2 sunken allen screws from the rear (which I shall refer to as bracket-X from now on).

The lower sliding bracket pin has rusted fast into bracket-X! (The boot must have let through water). Is it worth trying to free the pin? I've no idea how far into bracket-X it's rusted. Bracket-X has "CN5 1554/1 2035" engraved on the side of it. I don't see this item on IPD / other Volvo parts site. Salvage yards are few and far between in these here parts.

What's the official name for bracket-X and how do I come by another?

Thanks,

Rob

Retired MVS Contributor · Post by **Retired MVS Contributor** » 15 Aug 2010, 07:04

i would soak them with P-Blaster, an excellent penetrating oil and try to get them out because, even if you buy rebuilt calipers, the pin is not considered part of the caliper and will not come with it...But even at that, if they will not come out, both FCPGroton and IPD sell the calipers, the pins and the boots...I am not sure what bracket "X" is, but the pins are threaded into the caliper itself and retain the pads...

Retired MVS Contributor · Post by **Retired MVS Contributor** » 15 Aug 2010, 09:12

rob2volvos wrote:Funny this should be reported now. I have a 1992 740 whose brakes were performing poorly. I removed the wheel and the caliper on the drivers side. I hung up the caliper on the suspension spring. Then I removed the bracket (what's the name for this item?) which is held in by 2 sunken allen screws from the rear (which I shall refer to as bracket-X from now on).

The lower sliding bracket pin has rusted fast into bracket-X! (The boot must have let through water). Is it worth trying to free the pin? I've no idea how far into bracket-X it's rusted. Bracket-X has "CN5 1554/1 2035" engraved on the side of it. I don't see this item on IPD / other Volvo parts site. Salvage yards are few and far between in these here parts.

What's the official name for bracket-X and how do I come by another?

Thanks,

Rob

Wait a minute...You faked me out...If you removed the caliper and hung it on the spring, you removed the pins the caliper slides on...