Ideas needed to break free frozen brake calipers!

[HuskyMan]

I understand that in most cases compressed air can be used. However, in some instances the calipers are so frozen one DIYer has developed a system using a diesel injector pressure tester to use 3000 PSI to break the stuck caliper free.

I'm wondering if there might be a less expensive solution, any ideas?

[Junkman]

Compressed air is the standard method. Any way of rigging pressurized fluid that doesn't compress should push the pistons out. There are posts where people have separated the halves and had successful rebuilds. A BFH should work if halves are separateed. The FSM says not to separate. I probably would simply buy remanned and let the current go back as cores. Life is short but the choice depends on money and how much fun you're having messing with calipers.

Buy remans locally in case they have to be returned and keep your cores until you are well satisfied that the new calipers are working.

[Alec300SD]

Grease gun works well.
The flexible hose on a grease gun fits the brake line threads on the caliper.
I used mine to remove the pistons from the calipers on the junkyard wagon calipers I was going to rebuild.

The bores were either marginal or excessively scored an all the sets I bought from the junkyard.

Instead of rebuilding the marginal calipers, I bought new ATE wagon calipers for
the rear brake upgrade on 'Rena 2.0' that was transferred over to 'Stormcloud'.

Just acquired another set of new ATE wagon calipers for a rear brake upgrade on "Desert Rose'.

Good luck with your brake job.

[tyl604]

Agree. Life is too short and the rebuilds are cheap. Go with a rebuild.

[Father Of Giants]

In my mind sticking = corrosion, depending on the severity the pistons and bores might be too far gone. Or you're lucky and they're rebuildable.f

Like another member said, use a grease gun, but adopt it to use liquids instead of grease, fill with brake fluid and go to town.

Resealing the calipers is EASY and cheap, and you don't have to split them to reseal.

[torsionbar]

Originally Posted by HuskyMan

I'm wondering if there might be a less expensive solution, any ideas?

I've found using the brake pedal is the easiest and most effective tool. You'll never put more pressure into the caliper than by stomping on the brake pedal. Pull the pads out of the frozen caliper first, so the pistons have room to travel. The rotor will keep the pistons from shooting out.

[ah-kay]

Originally Posted by torsionbar

I've found using the brake pedal is the easiest and most effective tool. You'll never put more pressure into the caliper than by stomping on the brake pedal. Pull the pads out of the frozen caliper first, so the pistons have room to travel. The rotor will keep the pistons from shooting out.

X2. Remove the old pads but shim the gap with something so the gap is less than 1/4". Push the brake padel to push the piston out gradually. Re-shim and repeat. It should work.

[optimusprime]

Large G clamp and penetrating oil . If a rear caliper i have drilled a hole in the rear of the caliper in line with piston .Tap piston out .Then tread the hole lock in a bolt cut to size cut off the end This is a temp repair like when i was in the gobi desert broken down with no rear brakes.Replace when i returned home .

[Diesel911]

you can on one side shoot that penetrating oil into the bleed hole if you remove the bleed screw (which is also sometimes rusted in place). You can also use a propane torch to heat up the outside of the caliper where the piston rides. Heat also sometime ficilitates penetrating oil getting into places.

Since I split the calipers there would be plenty of room for the stuck caliper pullers that you might get as a free rental at the Auto Parts store and there is also sort of a cube with holes for a breaker bar in them that you stick into the open part of the caliper piston and try to get the piston to rotate and try to pull out at the same time.

This is what I did but it did it very carefully see pic.

[vstech]

Originally Posted by torsionbar

I've found using the brake pedal is the easiest and most effective tool. You'll never put more pressure into the caliper than by stomping on the brake pedal. Pull the pads out of the frozen caliper first, so the pistons have room to travel. The rotor will keep the pistons from shooting out.

actually, since you are doing one side at a time...
pull ONE pad only... then hit the brakes, and the piston pops right out.

rinse and repeat as necessary...

[tyl604]

Isn't it recommended never to split the caliper apart?

[vstech]

Originally Posted by tyl604

Isn't it recommended never to split the caliper apart?

yup.

splitting them requires unobtaneum crush washers... so splitting them is taking a chance on leaks.

[Diesel911]

Originally Posted by tyl604

Isn't it recommended never to split the caliper apart?

That is what the Mercedes Service Manual has. In my Case I had been splitting calipers since the 1980s on other vehicles with no issues and did not see any thing special about the calipers Mercedes uses.


The rebuilders split the calipers in order to replace the O-ring that goes between the Calipers so I did nothing that the rebuilders would not have done.


The real hold up to splitting the calipers is that most caliper rebuild kits don't come with any O-rings to go between the caliper halves.
However Centric has rebuild kits with those O-rings included.


If you think the Mercedes Calipers need careful attention the front calipers on my Volvo each have 4 pistons. I also split the calipers on my Volvo too.


The last issue was finding a torque for the 12.9 metric bolts. It is not in the service manual.


It has all been covered in other threads including the to split or not to split arguments.

[HuskyMan]

I appreciate all the ideas..... peachparts forum members have to be amongst the most creative auto repair techs anywhere!