Removing seized brake pistons with a grease gun

[JOEPRO]

I am rebuilding the rear brake calipers on my Merc 190E. The pistons were seized solid, would not budge with 125psi air.

So I cut the end off an old brake hose and welded on a grease fitting. The grease gun made easy work of breaking loose both seized pistons



Just sharing the tip - first time I have tried it and I am surprised how well it worked.

 

[Blobber]

Done it a few times but it takes a bit of cleaning to get the grease out

 

[JOEPRO]

This is what I started with.



Blasted:



Classic MB calipers dont give much trouble but when they do seize its usually this rust on the atmosphere side of the bore itself:



Sand that off



New seal kits are inexpensive and the original pistons buff up like new so these will go again and operate as good as when they were new in 1989.

One small detail often overlooked is the pistons have a small clearance on them. This is for even pad wear which means they are directional and must be set up correctly. Hence there is a tool for that





I will clean these again then fit the new seals and paint them.

 

[chrismac]

Milwaukee grease gun obviously!!

 

[JOEPRO]

Milwaukee grease gun obviously!!

I wish!

Just a standard hand pump manual grease gun.

 

[mtt.tr]

It does work,but be careful if it won't budge you don't want to be releasing high pressure grease

 

[JOEPRO]

It does work,but be careful if it won't budge you don't want to be releasing high pressure grease

This method is very safe and controllable. When the pistons pop out the grease just oozes out slowly. The geease stays together and doesnt spray like compressed air would spray residual brake fluid at you or make the pistons projectiles!

 

[BrokenBiker]

Oohhhhh im saving this idea...I have an air powered grease gun that gives 1 shot at a time that would be good for this...guess thats another adapter I need to make

 

[bricol]

Years ago, I had a Lancia integrale 16V single pot caliper in my hand, fingers around the reaction frame to hold it. Just blowing compressed air over it to blow the crap off . . .

Air went down the open hose connection, blew the piston out far enough out so it hit my fingers and then jammed, cockled over . . . it HURT!

Fingers now trapped, the caliper went in a big vice and the piston went back, didn't care how, it was going back.

Fingers came out - bruised, but intact!

 

[Bsmith]

A friend advised me to try the grease gun on a stuck bmw fron calliper, indeed it worked well, I didnt know the idea was so widely used.

 

[Argonman]

Good job.
I always make a point of a thorough clean of the seal housing (the slot where the seal sits). Corrosion in the slot can displace the seal and can cause a sticky piston. I use a mini circular wire brush fitted to my dremel.

 

[JohnH]

Used to do it all the time

 

[Agroshield]

Done it a few times but it takes a bit of cleaning to get the grease out

Would it be possible to use an oil gun instead of a grease gun to make cleaning easier?

 

[JohnH]

Would it be possible to use an oil gun instead of a grease gun to make cleaning easier?

Think that would be really messy, when the piston popped out.

I dont find the grease is that bad, especially when its already damp with brake fluid.

 

[addjunkie]

Milwaukee grease gun obviously!!

Much as I think these are very good as I have one, they certainly put grease consumption up!

 

[roofman]

I have in the past undone one bolt on the caliper carrier on the car or van, swung it up and wrapped a small towl around it to soak up the fluid and used the brake pedal to pump the pistons out...done the same on a bike come to think of it too.

 

[frank horton]

For collectible bike n cars where new callipers are unavailable there are one or two firms that will reborn and. Sleeve the calliper and make new piston's
My friend does this with some weirded bikes he rebuilds…
Think he uses brass for the liner and St/st for the piston…and all new seals…

 

[zzr1200]

Stop playing about use a porta power pump unit, 10,000 psi will move it.
Just don't get your pinkies in the gap when it moves and only oil, no grease to clean out....

 

[Beanwood]

Surprised me how quickly a stuck piston came out from the bike rear calliper when I used compressed air- grease looks like a good option for anything even slightly more stuck!!

 

[E T]

I should have tried that trick a couple of weeks ago.
I never use the rear brake on my bike and after 27 years of non use one piston was stuck solid. Wouldn't budge with compressed air.
I ended up splitting the calliper. Turned a steel slug on the lathe with a M10 thread in the middle. Welded that in the piston and made a slide puller of some M10 allthread. Worked a treat. New pistons and seal set and it's as good as new.