Help! Rear caliper piston wont compress

[CoolRod]

Took the rear calipers off to paint them and the right rear caliper piston won't compress far enough to reinstall. I am using the caliper tool I rented from O'Reilly's. I've used these tools before with good success but this piston only turns maybe a half turn before it stops. It just needs to compress maybe another 1/8" but it won't budge.

The caliper has very little to no brake fluid in it. I drained them when I removed them from the car.

Any tips?!?!

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[sk47]

Hello; Are you sure bout two things? One is the pistion the type that presses in or the type that has to be turned (screwed) in. My car has the screw in sort.
The other is to be sure the piston is square in the bore of the cylinder? Being cocked a little will cause a jam. Look at the surface of the cylinder to check for irregularities.
Had a pickup caliper in which the factory piston did not want to smoothly go into. Would only go in about half way. I used a hone on a drill at low speed to work the inner surface. I do not know what happened to cause the issue.
good luck

 

[K4fxd]

Since it's off the car take it apart and clean it. Probably will need new seals but should replace them anyway.

 

[Hack]

Since it's off the car take it apart and clean it. Probably will need new seals but should replace them anyway.

Either this (rebuild kit) or a new caliper. You might need to hone the bore and deburr the piston if there are burrs from the piston getting jammed in there. You definitely want the piston to move freely before you reinstall.

 

[CorvZ061]

do you have the park brake handle up or down? dumb question, I know.

 

[DougS550]

Took the rear calipers off to paint them and the right rear caliper piston won't compress far enough to reinstall. I am using the caliper tool I rented from O'Reilly's. I've used these tools before with good success but this piston only turns maybe a half turn before it stops. It just needs to compress maybe another 1/8" but it won't budge.

The caliper has very little to no brake fluid in it. I drained them when I removed them from the car.

Any tips?!?!

When I have to compress a caliper, I always open the bleed valve some before I compress the caliper puck. Then after install I do a quick bleed. Good luck

 

[Pistol_91]

Take cap off brake fluid reservoir. Use right tool to screw it back in. Done.

 

[Andy13186]

You have to screw these pistons in on the rear. Amazon has a kit that you can use, https://www.amazon.com/BTSHUB-Profe...118&sprefix=piston+screw+brake,aps,111&sr=8-3

You can do it with needle nose pliers if you are careful, just put the noses in the indentations on the piston and screw it in.

 

[CoolRod]

You have to screw these pistons in on the rear. Amazon has a kit that you can use, https://www.amazon.com/BTSHUB-Professional-Caliper-Compression-Replacement/dp/B08G1QLCXK/ref=sr_1_3?crid=BMRTXALW3BYJ&keywords=piston+screw+brake&qid=1705277118&sprefix=piston+screw+brake,aps,111&sr=8-3

You can do it with needle nose pliers if you are careful, just put the noses in the indentations on the piston and screw it in.

I used a kit a similar kit that I rented from the parts store. What ended up working for me was loosening the brake line banjo bolt. I guess that released the "pressure" inside the caliper. Never had that problem before so I will have to remember that next time.

 

[CoolRod]

When I have to compress a caliper, I always open the bleed valve some before I compress the caliper puck. Then after install I do a quick bleed. Good luck

This is what ultimately ended up working for me.

 

[DougS550]

This is what ultimately ended up working for me.

Sorry I didn't reply faster. My normal practice of opening the bleed screw when compressing us mostly to bleed the fluid in the caliper. Later

 

[K4fxd]

My normal practice of opening the bleed screw when compressing us mostly to bleed the fluid in the caliper. Later

Also prevents blowing the master cylinder seals.

 

[Pistol_91]

That crazy tool isnt necessary. They sell a tool at any local auto parts store for like 12 bucks that goes on a 3/8th ratchet.
Here...
https://www.napaonline.com/en/p/BK_...6kPzrRoCiFUQAvD_BwE&gclsrc=aw.ds&gad_source=1

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