Diagnosing Brake Calipers - PeachParts Mercedes-Benz Forum

bigfredb · #1 11-03-2009, 01:17 PM

I have an 83 300SD.

How can I tell if a brake caliper is bad?

Also, how can I tell what type I have on there now (ATE, Bendix, or ???)?

toomany MBZ · #2 11-03-2009, 02:02 PM

If you're having braking problems, but pull them and visually inspect. If you see any torn seals around the piston, time for a replacement.
Bendix calipers have a thin bent wire as a pad retention device, ATE's have a two piece, flat metal item riveted in the middle.

tobybul · #3 11-03-2009, 06:30 PM

Quote:

Originally Posted by toomany MBZ

If you're having braking problems, but pull them and visually inspect. If you see any torn seals around the piston, time for a replacement.
Bendix calipers have a thin bent wire as a pad retention device, ATE's have a two piece, flat metal item riveted in the middle.

It should also say Bendix or ATE right on the caliper

bad caliper will either be leaking or seized. leaking will be obvious and seized will be..... well, seized.

swheele2 · #4 11-03-2009, 10:33 PM

If one caliper is sticking the affected wheel will probably be pretty hot after even a short drive. But, like everyone else said, pull off the calipers and take a look.

benhogan · #5 11-04-2009, 01:44 PM

Quote:

Originally Posted by swheele2

If one caliper is sticking the affected wheel will probably be pretty hot after even a short drive. But, like everyone else said, pull off the calipers and take a look.

or you could smell each wheel after a good drive. the sticking caliper will have a distinct 'burned' smell.

snookwhaler · #6 11-04-2009, 06:15 PM

If you know some one that has an infrared thermometer... This is a great way to check your brakes.

I'm having a caliper problem too and am in the middle of diagnosing. Better to rebuild the ones you have (if you can) before buying rebuilt ones from the local store.

You will know once you get them off and get the seals/pistons out if they need to be "replaced". IE: lots of rust on the piston and or in the bore... Replace them with good rebuilds.

On the old calipers, a little bit of rust can be cleaned off and you can put a seal new seal kit in there. The heat shields can be a PITA to install on the fronts. Plus, you have to line up the piston perfectly. The rears require to put the piston in a certain way to prevent brake squeal. It is not that difficult if you just take you time.

There is some info. on this in the resources section under the DIY links. Plus lots more in the search.

As stated above.... ATE or Bendix will be visible on the calipers and always rebuild or replace in pairs on the same "axle".

toomany MBZ · #7 11-04-2009, 09:19 PM

The brand names are not always easy to make out on 26 year old calipers which is why I gave my response. A quick viewing will let you know, instead of trying to decipher through the rust.

snookwhaler · #8 11-04-2009, 09:29 PM

Don't rule out a collapsed brake line either. If they are original, chances are that they are falling apart internally.

They are only 10 to 12 bucks a piece at NAPA. I replaced them all when I did my rotors a few months back.

snookwhaler · #9 11-07-2009, 04:08 PM

Not sure if this will help. So, here goes....

My car has a very slight pull to the left under very hard braking.

I went through and replaced all the brake hoses on my car today. In the process I pulled every caliper for inspection. I started at the rear and worked my way forward.

On the very first caliper (passengers rear), I found that the inner caliper was hanging up and very difficult to push back in using the old c-clamp.

Here is how I diagnosed. I pulled the caliper off, removed the pads and suspended it in the air with some safety wire. I used a c-clamp to squeeze the calipers in. I then went and pushed on the brake pedal 2 times and came back to see what happened at the caliper. The outer piston moved out about 1/4". I then c-clamped the caliper back in and left the c-clamp attached to the outer piston holding it in. The outer piston went back in very easy. Then I went back and pumped the brakes 2 more times. The inner piston moved but not as much as the outer. Also, trying to get the inner piston back in was a PITA. I actually had to remove the caliper and beat the piston back in with a hammer and a flat bar. I repeated this procedure 2 times just to be sure. The inner piston on that caliper is probably rusted. It also has a chip on the edge of the piston. So, I'll probably wind up replacing them both on the rear instead of just rebuilding.

I repeated this procedure on the rest of the calipers and replaced the brake hoses at each wheel. Then I pressure bled the whole system with ATE DOT 4 Blue and re-greased the backs of all the pads. The rest of the pistons on all the calipers moved very easy.