I think I have a caliper issue with one of my front brakes. It seems to want to lock up on occasion. I plan to do a full brake job on the car. I will replace front rotors and calipers. Is there anything I should check besides the calipers. Would a defective master cyl cause a lock up like this? Should I just replace the thing on principal, car has about 208K.
Is there any consensus regarding ATE vs Bendix for the calipers? The rotors actually look good but I did overheat one of them very much so I believe they should be replaced anyway.

perfect time to repack or replace the wheel bearings....and the rubber brake lines.....unles those have been recently done. Rubber hoses can swell internally holding presure....if they look original it may be time to replace them.

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Not rebuildable? (The calipers)

I have Bendix on the SD and ATE on the SDL.

The ATE on the rear's were easy to rebuild.

The Bendix, with the heat shields, were a PITA.

I don't think there is any preference with regard to stopping power.

Definitely repack the bearing and use new seals. Watch the end play. You want it down below .001, but, this is very difficult to achieve by feel.

rmmagow,

Check the brake hoses going to the calipers to make sure they are free flowing. Sometimes the brake hoses swell shut and this keeps the calipers from releasing properly.

I wouldn't replace the calipers unless you are certain it is them that is causing the problem. My '80 300SD has more miles than your car and the calipers seem to work perfectly. If your calipers don't leak and its easy to push the piston back in, they are OK.

Since you said only one caliper is locking up it is unlikely the master cylinder is causing the problem since it is connected to both calipers.

P E H

Thanks Folks.
Finally got a chance to remove the caliper. The pins are rusted in solid, the pads are REALLY tight in the caliper. I am going to order a pair of ATE's loaded. I can't tell what's on there now but I'll just do both fronts to the same make. I understand this is acceptable. Came off pretty easily and the disc spins freely and quietly. I'll repack 'em anyway. What are the parts called that hold the hub in place, the part that you tighten up with an allen wrench? The screw is a bit worn and I probably should replace that too. Thanks for all the advice.

I would urge you to reconsider purchasing all new calipers.

If the pins are rusted solid and the pads are corroded in the caliper, you can't judge the performance of the caliper itself.

Please try this before continuing:

Remove the caliper and brake hose from the vehicle and try and force the pistons back into their bores. If you are able to do this, and the boots are intact, you don't need new calipers.

Polish or replace the pins. (available as loose parts for cheap)

Get a small wire brush and thorougly clean the ground surfaces on the caliper where the pads ride (four surfaces per side)

Get a small packet of brake lube from Poop Boys and add just a dab of lube to the caliper surfaces where the pads ride (NOT MORE THAN A DAB).

Put it all back together and bleed the brakes and you are done.

rmmagow,

Its called a spindle nut.

How could the screw get worn, its essentially a non moving part.

I agree with Brian, check the calipers before replacing them. Why spend $200 for something you don't need. If the pads are tight, just file or grind the edges enough so they fit.

If it ain't broke, don't replace it.

P E H

Yeah, I have decided to try and fix them first. My Jag is acting up and it's going to need the money more than the 123. The screw isn't worn, the hex head seems to have been abused by a PO. I'm guessing he didn't have the right tool and just forced something in there to loosen it. I've got too many old cars and not enough time (or money) to keep them all up and running. I aught to put my old Ponton back on regular registration and drive it daily. At least nothing seems to ever break on that old beast!

Well, I'm screwed. The calipers will need to be replaced. The one that was acting up is a total mess, heat shields rotted away, piston front all rusted and distorted, rubber seals torn. Off to Phil's !

The calipers are very easy to rebuild, especially compared to the Toyota and Nissan units I've done.

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rmmagow,

Check AutoZone for rebuilt calipers. They had rebuilt ATE for my '79 300SD when others didn't. They were about $90 each and gave me next day delivery for an extra $8. Lifetime guarantee for what that's worth.

The reason I didn't rebuild old caliper myself is because the casting was cracked and was not rebuildable.

P E H