Topic: Seized Caliper Question

[djbinzo]

I am having a hell of a time getting my CB750 caliper apart.  It is on the bench, and I have tried the grease gun method with no luck.  Any suggestions on how to get things apart?

[lrutt]

Man, if a grease gun won't do it.  I could only say to find someone with an ultrasonic cleaner and let is set in there for a while then try the grease again.

[grumpy]

I blew mine out with 125psi air but, yeah, if the grease gun didn't do it then

Mebbe soak it in alcohol? It dissolves dried brake fluid....

Heat the caliper body & hit the piston with electronics cooling spray to shrink it, then the grease gun??

 

[djbinzo]

Heat was my next step. 

The grease gun made short work of the other calipers I have done, but it is doing nothing to this one.

As a side note, what kind of prep are people doing to the bore on the caliper before reassembly?  I was thinking about a light hone.

[Duke McDukiedook]

Yep, 120psi will do wonders to a stuck piston.
Have it facing a hard surface directly when you pull the trigger though, pistons can make nasty projectiles.
Just clean it up with steel wool or fine grit sandpaper, no need to hone it.

[Magpie]

Here's a stupid question, I know it's stupid because I didn't do it the first time, have you backed out the fitting you're putting the grease gun on to make sure the grease is in fact going into the piston area? I've had several very stuck pistons and the grease method worked every time.
Cliff.

[patrickd]

They freeze up cause the pads corrode to the caliper itself. Try taking the caliper apart and spray some pb blaster around the edge. Then hit it with a propane torch all the way around. Tap it with a hammer lightly while heating. Also you could try hammering the pad backwards.. Drive it in slightly to break it free then screw a 10mm grease fitting in the hole where the line screws in and pump it up with the grease gun. it will come right out..
Then after the piston is out clean the groove under the rubber ring real good. The buildup under the seal keeps the piston from retracting when you let off the brake. 

[fmctm1sw]

I've always had good luck just connecting it to a good master cylinder. 

[Porscheguy912]

IMO if the grease gun method didnt work then look for a used caliper online and throw this one in the parts drawer to be messed with at a later date.

That thing is prob so funged up that you will have a hell of a time getting the surfaces smooth again once its out.
Good luck

[pg13]

so all this talk is about getting a stuck piston out right? well im having trouble getting the pad off. same tricks? should just kinda slide right out once the caliper is apart right? i cant see anything else holding it in.

sorry to hijack your thread by the way

[patrickd]

I have never seen a piston be stuck. It's always the pad. Scroll back up to where I posted earlier on this thread. Try using a hammer to pound the pad further into the caliper just a bit to break the corrosion between the edge of the pad and the caliper. Then use the grease gun. It works I had the same problem this spring on an old caliper that had been sitting in a barn for 20+ yrs.

[djbinzo]

To update this a little bit...

I pulled the bleeder off with the grease gun installed, and go no grease out-- but the gun is pumping grease.  So, this tells me that something on the inlet side of the caliper is blocked.  Any suggestions on how to chase/clean that out?

[patrickd]

leave the bleeder in and closed. Put the 10mm zerk in the hole that the brake line goes in. 

[grumpy]

To update this a little bit...

I pulled the bleeder off with the grease gun installed, and go no grease out-- but the gun is pumping grease.  So, this tells me that something on the inlet side of the caliper is blocked.  Any suggestions on how to chase/clean that out?

The inlet is just a hole - no turns or hidden galley - goes right into the space behind the piston.
Pretty odd that it's plugged...
You must have mega crud in there. Soak the whole thing in your fav rust busting oil & see if it helps.
Try shooting your grease in from the bleeder hole?

[patrickd]

like I said earlier. You can drive the pad into the caliper a tad to break the bond of the corrosion, Take the other side off and give the cylinder side pad a couple of good whacks with a hammer,then pump it full of grease. Use the line hole for the 10mm fitting. Leave the bleeder closed. I know it will come out. I have done it before to calipers that were totally locked up..
Lots of times air won't do it cause the compressor only goes to say 150 psi. A good grease gun pushes 10,000 psi or more..

[honda750k]

I generally just use grease guns on stuck pistons.  If the methods above fail, you may as well just find another caliper and be done with it. they're not super hard to find, you just need to know where to get em.