1994 850 Replacing rear brakes and cylinder won't compress

[chubbylumpkins]

So I was successful in replacing all my brakes on my own without any help!!


Unfortunately, I have been unsuccessful in replacing one of the pads one passenger side rear...No matter what I do, I cannot seem to get the cylinder to compress in order to slide the last pad in. I don't have a compression tool, so I used channel locks on all the others and it worked out quite well...anyone have any suggestions for a solution?

[dosbricks]

Welcome to the forum. Did you loosen the cap on the reservoir and check it periodically to ensure it doesn't overflow? Try re-inserting the worn pad and step on the brake to unstick the cylinder. Then use a strip of wood under your Channel Locks to distribute the force across the cylinder.

[scot850]

All good suggestions, but you can also bleed some fluid out of the bleed screw if it is not seized (don't force it or it will shear off ruining your caliper). This puts less stress on the master cylinder seals (a Volvo dealer in the UK blew the seals out of a 240 forcing the pistons back in). Check the master cylinder level, and only push the cylinders back in with the lid loose if not using the bleed screw method. Could also be the caliper is rusted solid! This is common.

Good luck,

Neil.

[Ozark Lee]

You can also try to put an old pad in and then use a screwdriver to pry it back in. Having the old pad in place keeps things more or less square and should prevent the piston from getting cockeyed and binding.

This is probably a good excuse to just buy the tool though. I think the last one I bought was around $10.00 and it greatly simplifies your life. They don't wear out unless you do something stupid like I did when I left it on the driveway behind the wheel and broke it as I backed up my Suburban. The one I bought to replace it has lasted for 25 or 30 brake jobs over the years and it is still going strong.

...Lee

[abscate]

If it doesn't go back in with the bleeder eased, it's usually an indication the piston is starting to seize in the caliper. This will quickly wear out your pads of course. Keep an eye on that wheel and check it for excess heat after each drive.

[jreed]

I'm going to be replacing the rear pads on my '97 855 GLT in a weekend or two, and I was planning to follow Scot850's advice and open up a bleeder nipple when trying to compress the pistons back into the calipers. Hearing about the compression tool makes me curious... which type of compression tool do you have and where did you get it? Any advice and recommendations would be welcome!

[abscate]

I use the frame of a two arm gear puller. Remove the arms, now I have a threaded screw into a cast metal cross piece. I put a large socket on the end of the thread to protect the piston, then ratchet the thread/socket combo on the piston to push it back.

I always ease the bleeder, push the fluid out of the bleeder, then bleed fresh DOT4 into the caliper until it runs clear. I solo bleed by:

- just cracking the bleeder enough so that I have pedal resistance, and thus brake pressure, to push air out
- putting the tubing up high into the springs, so that air automatically rises out of the caliper.
- Slowly pushing down the brake pedal and forcing new fluid into the system

I haven't had to enlist SWMBO to help me bleed this way in 3- years.....BUT......

ANY DOUBTS at ALL.....take it to your INDIE and have it power bled.

[Ozark Lee]

which type of compression tool do you have and where did you get it?

I use one like this:

https://www.fcpeuro.com/products/brake- ... Mgod4lwA_Q

I didn't actually buy it from FCP, any chain auto parts store will have them.

...Lee

[scot850]

I also bought an identical piston compressor from my local autoparts store in Canada for around $12. Simple but works well. I did find in one case it did not go deep enough, so dropped a small socket into the caliper piston to give greater reach.

Neil.

[FLXC90]

Chubby: can you see the side of the piston? Is the boot torn? Is there any corrosion visible? If so, you need to replace or rebuild the caliper. It may retract, but it will leak or not seal internally.