86 420SEL frt brake rotor & pad replace - stuck piston

[billb95]

Howdy!

Short and not-so-sweet - ABS warning light and terrible brake grab happened as I was pulling into my garage. I had been warned they were close to going, but had no idea that close!

So I have already put new rotor on driver side:



and now I go to work on getting the new brake pads installed and the inside piston seems frozen!



I was able to get the outside piston in ok; but that inside one just won't budge. As you can see in the above photo I have the brake fluid drained - I thought that would relieve the pressure allowing both pistons to go in easily. I've tried using a very large wrench to fit inside the piston and push it in, but no go.

I really don't want to mount the caliper back on the hub(?) - I fear I'll risk damaging the new rotor.

So what is the right way to fix this situation? I'm not looking for the easy way, I'm looking for the right way. Should I pull the new rotor off and put the old back on? Is this where I went wrong in the process - I should have changed the pads first, then the rotor?

Thank you for the guidance.

Bill

[porkface]

a large c-clamp, patience, a small pick and wd40. with the small pick, remove the dust seal on the outside. don't poke any holes-patience. now for the wd40. more patience. install a brake pad and then the clamp. tighten slowly. damn, more patience. leave the bleeder open just in case. go slow and evenly. had to get calipers once in a while, but i've manged to save more this way. good luck, chuck.

[Jerry Cohen]

Just curious, on the suspect caliper, were both pads equally worn?

If not, you might want to think about a reman caliper.

[billb95]

Originally Posted by Jerry Cohen

Just curious, on the suspect caliper, were both pads equally worn?

If not, you might want to think about a reman caliper.

Good point! The car has almost 300k miles on it.

Will review tomorrow. Thanks again to everyone for the help.

[t walgamuth]

The rotor is very very tough. When I change pads I start by driving a medium straight screwdriver in between the pad and rotor. Once I create about 1/4" of clearance there I put in a very large screwdriver I keep around just for prying on things. Its about 18" long. With the big screwdriver I pry the pad all the way back so that the brake cylinder is fully retracted.

If I cannot pry it back with my big screwdriver its time for a new caliper.

90% of the time I can pry them back.

If the new pad is to tight to go in easily I use my grinder to dress the edge of the pad so that it slips in easily.

Don't worry about damaging the rotors or the calipers. The stresses they are subject to in their dialy life of braking the car make your prying on them insignificant.

[billb95]

Originally Posted by Jerry Cohen

Just curious, on the suspect caliper, were both pads equally worn?

If not, you might want to think about a reman caliper.

I did order a pair of reman'd calipers. Excellent time to paint them as well, I assume. So multiple questions now:

1. Can I use the kind of heat resistant paint used on gas grills?

2. My 3 ton jack stand is questionable for this car (read as: I have no clue as to whether this is adequate to support the weight of the front driver side corner of the car). I have a 7 ton jack but it is too tall to go under the passenger compartment frame 'rail'. Any other jackstand locations I can use at the front of the car? Do I need to get a bigger hydraulic jack so I *can* get the 7 ton jack under the passenger compartment (on the frame rail)?

3. I also have new brake hoses (that go from the car to the caliper to the car). Is my best way to replace them just to cut the old ones to get a socket on the car side to remove it?

4. Any other things that might be gotchas? I already have a mighty vac to bleed the brakes once this is all done.

Thanks again.

Bill