300SDL sticky brake caliper, how to remedy? - PeachParts Mercedes-Benz Forum

Father Of Giants · #1 06-26-2017, 09:52 AM

So I attempted to remove my caliper yesterday but the lip on the rotor was so massive I had to compress the pads a good bit to remove the caliper.

Is the piston sticky, if so how do I remedy it. What else could cause this?

Both pads still have plenty of material but are wearing faster in the inside rotor.

t walgamuth · #2 06-26-2017, 10:01 AM

In my experience if the puck is pushed so far out it gets cockeyed and sticks you can sometimes push it back in with a c clamp and get away with it.

If it is just stuck and is not cockeyed you are probably going to have to replace the caliper.

Diseasel300 · #3 06-26-2017, 10:25 AM

As suggested above, try compressing the piston all the way back into the cylinder. You might also try some brake lubricant on the caliper pins while you have the thing apart. Go for a ride. If it sticks again, you're probably better off replacing the caliper than trying to repair it. The tools and parts required to refurbish the cylinder cost more than a new caliper does. Unless you plan to do the whole car, or have several cars with brake issues, it probably isn't worth the money to buy the tools to DIY that job.

jay_bob · #4 06-26-2017, 10:28 AM

You might have overcompressed the piston to the point where the unworn area has caught the inside of the bore.

I would say you need new calipers (on both sides, never just replace one). And rotors too from the sound of it.

Brakes are too critical to take a chance on. I would definitely replace without question.

Father Of Giants · #5 06-26-2017, 02:39 PM

Welp, that throws the caliper rebuild out the window.

Looks like I'll work a double shift to pay for these calipers.

cfh · #6 06-26-2017, 03:01 PM

Replace both rotors on that axle. If the calipers are ATE you can get rebuild kits here on Peachparts.

I had the same problem once and when I rebuilt the calipers there was a lot of nasty goop in there. Everything was fine though once it was all cleaned out and back together. Made me realize I should have been flushing the brake system all these years.

I've heard horror stories about rebuilt calipers not fitting up right - if replacement rather than rebuild is necessary it would be better to start with some decent junkyard used calipers and rebuild them yourself, instead of buying rebuilt calipers.

Diesel911 · #7 06-26-2017, 03:18 PM

If the calipers can be rebuilt of not is determined by being able to get the caliper pisotons out and then inspecting the pistons and the cliper bore.

Typically the caliper bore has pitting from rust. The pitting cannot go all the way into the caliper seal area. After that you just sort of have to use your best judment if the pitting is too much or not.

there ought to be verious methods of removing the brake caliper piston on the internet or in this forum.

Father Of Giants · #8 06-26-2017, 04:57 PM

Quote:

Originally Posted by cfh

Replace both rotors on that axle. If the calipers are ATE you can get rebuild kits here on Peachparts.

I had the same problem once and when I rebuilt the calipers there was a lot of nasty goop in there. Everything was fine though once it was all cleaned out and back together. Made me realize I should have been flushing the brake system all these years.

I've heard horror stories about rebuilt calipers not fitting up right - if replacement rather than rebuild is necessary it would be better to start with some decent junkyard used calipers and rebuild them yourself, instead of buying rebuilt calipers.

Sounds like a great idea.

Quote:

Originally Posted by Diesel911

If the calipers can be rebuilt of not is determined by being able to get the caliper pisotons out and then inspecting the pistons and the cliper bore.

Typically the caliper bore has pitting from rust. The pitting cannot go all the way into the caliper seal area. After that you just sort of have to use your best judment if the pitting is too much or not.

there ought to be verious methods of removing the brake caliper piston on the internet or in this forum.

Will do

Father Of Giants · #9 06-26-2017, 05:35 PM

Well my local scrapyard doesn't have any cars with compatible calipers. Don't know how i'm going to adress this.

Junkman · #10 06-26-2017, 06:56 PM

The car is inoperable as is. You can take the caliper apart and get an idea of whether it can be rebuilt. Rebuilds used to be standard procedure.

Compressed air blown into the hole where the hose connects will blow 1 piston out. Reinsert that piston only far enough to seal the air, tie it in place with a rag or block of wood or something and blow the other piston out. You will need a cylinder hone to clean up the bore. Add $15 to the cost for the hone unless you have one from days gone by.

If you're short on cash or want to mess around, try building. Otherwise, buy calipers, rotors, hoses & perhaps bearings seals and wear sensors. There are 2 brands of calipers they are interchangeable but need to be in sets. Buy the least expensive brand but buy locally in case you need to return. Keep your core until 2 weeks after the install is working.

The 2 brands of calipers technically take different thicknesses of pads. The pad suppliers have gone to the thinnest of the 2 pads so that the PN is interchangeable. I will buy low dust pads the next time because I don't like the dirt and also don't wash the car frequent;y.

Mxfrank · #11 06-26-2017, 06:57 PM

Is this really anything more than a worn rotor? It sounds like you were able to push the pads back in without problem.

If you think it's releasing slowly, the first thing to ask is how old the hose is? Hoses swell internally before the damage is visible on the outside. This can block the flow of fluid.

Father Of Giants · #12 06-26-2017, 07:42 PM

Quote:

Originally Posted by Junkman

The car is inoperable as is. You can take the caliper apart and get an idea of whether it can be rebuilt. Rebuilds used to be standard procedure.

Compressed air blown into the hole where the hose connects will blow 1 piston out. Reinsert that piston only far enough to seal the air, tie it in place with a rag or block of wood or something and blow the other piston out. You will need a cylinder hone to clean up the bore. Add $15 to the cost for the hone unless you have one from days gone by.

If you're short on cash or want to mess around, try building. Otherwise, buy calipers, rotors, hoses & perhaps bearings seals and wear sensors. There are 2 brands of calipers they are interchangeable but need to be in sets. Buy the least expensive brand but buy locally in case you need to return. Keep your core until 2 weeks after the install is working.

The 2 brands of calipers technically take different thicknesses of pads. The pad suppliers have gone to the thinnest of the 2 pads so that the PN is interchangeable. I will buy low dust pads the next time because I don't like the dirt and also don't wash the car frequent;y.

The two brands being Bendix and ATE?

Quote:

Originally Posted by Mxfrank

Is this really anything more than a worn rotor? It sounds like you were able to push the pads back in without problem.

If you think it's releasing slowly, the first thing to ask is how old the hose is? Hoses swell internally before the damage is visible on the outside. This can block the flow of fluid.

The hose is probably original or very old. Yes, I was able to retract the pads, but they started rubbing again.

I'm getting too ahead of myself.

THANKFULLY this is near me.

https://norfolk.craigslist.org/ptd/6193894558.html

I'll stop by there ASAP to look for some ATE caliper equiped calipers if it has to come down to that.

jay_bob · #13 06-26-2017, 08:18 PM

Good thought from Mxfrank that maybe it's your brake hoses swelling up acting like a check valve.

I would try that first, if you are short on funds.

Father Of Giants · #14 06-26-2017, 11:15 PM

Quote:

Originally Posted by Diseasel300

As suggested above, try compressing the piston all the way back into the cylinder. You might also try some brake lubricant on the caliper pins while you have the thing apart. Go for a ride. If it sticks again, you're probably better off replacing the caliper than trying to repair it. The tools and parts required to refurbish the cylinder cost more than a new caliper does. Unless you plan to do the whole car, or have several cars with brake issues, it probably isn't worth the money to buy the tools to DIY that job.

Caliper pins? How do I get to those?

jay_bob · #15 06-26-2017, 11:29 PM

The caliper pins are the two cylindrical bolts that hold the two sides of the caliper together.

The ones that come out when changing the pads.