1983 240d manual all 4 calipers not retracting
 

Howdy!

I couldn't find this exact problem discussed but if there's a link I missed, I'll gladly read it.

Back in September I got my 240d worked on. This included a new master cylinder and new lines to the clutch pedal.

Then in November my alternator died.

Finally got that fixed in January.

Then two weeks ago I was pulling into my driveway and heard a weird noise. The car became difficult to drive (my driveway is on a slight incline) and after I got it level, I could barely move the car by hand.

I finally got a chance to look at all four calipers and they were all stuck closed on the rotors (also I need to change my brake pads).

I can get them to retract using pliers and not too much force. Reapplying the brakes they stick again. Bleeding the brakes (a bit, maybe 2-4oz) at one caliper did not seem to make a difference.

I have reached the end of my knowhow as far as diagnosing goes. What's likely to be wrong and what should I check out?

When the MC was replaced they did not replace the booster (afaik). I can do the work myself (those guys are shysters and soaked me good) I just don't know where to go from here.

Thanks!

Are you bleeding the brakes correctly?

Did you bleed the clutch?

Any fluid loss?

Have you replaced the rubber brake hoses?

theres probably other things that can go wrong but if all are locking up i'd bet its the master cylinder. if they put in a crappy rebuilt unit they can go bad quickly. i've found brake work to be the shoddiest, shadiest and most overpriced of any auto repair. sorry if you got screwed :(

Jack up each wheel. This will allow you to see if the wheel turns easily. Buildup of rust on the rotors surfaces will wear off fast if an issue. Have a good look to see. Remember the back wheels will not turn unless they both are off the ground.

You may have one or two sticking calipers from sitting. Find out the ones they are first. There is a chance it is something else but usually calipers do not sit unused well.

If you find one that is really pretty much stuck. Either loosen the bleeder screw or bake hose at the caliper. Just in case the cause is other than the caliper. If the caliper remains pretty hard on after that then it is the problem. I guess the brake pad sliders could be immobile as well. Make sure the pads can slide on them.

Read the Text in the picture. When the O-ring is too stiff to act as a sort of spring to pull the Caliper Piston Back it the Piston does not retract and any sort of added gunk in side of the Piston Bore only makes things worse.

You have not got the emergency brake on? Something does not quite sound right with your post.

I would suspect very strongly it is the brake MC. Next time it happens try loosening the lock nuts on the brake line at the MC. There should be 2, one for the front and the other for the rear. Say loosen the front and let it bleeds a little brake fluid then re-tighen it. If it releases both front calipers then it is the MC not releasing, dirt trapped in the hole or bad rebuilt. Then try the other lock nut for the rear.

Good luck.

I can remeber having problems with a MC. Still, I do think that with all 4 caliper locked up, that would be my guess. I would loosen one of the bleeder screws. See if that, unlocks that caliper. Then I'd say it would be the hose or the MC. Then might go to one of the brake line connections on the MC. Un do it. See if that or those calipers unlock.
I'd probably replace the rubber brake hoses, if over 10 years old. I usually, try 5 years. I do not have direct experience with a hose collaping, and acting like a one way valve. I was walking my neighborhood, and one guy was working on an old Chevy truck. A front caliper was locked up. He took it to another neighbor who works as a mechanic. He undid the bleader screw, and then replaced the hose. Callapsed hose.
I do use one of the one man bleeders from NAPA. It is a small plastic bottle, that has a magnet on it, to attach to the frame etc. Works good.
Tom

If your pads are worn I suggest going ahead and replacing them. Putting the seal back into a different place in the caliper might well relieve the problem with sticking.

Check your Brake Hoses

See the whunter thread on brake hoses
http://www.peachparts.com/shopforum/diesel-discussion/339913-rubber-brake-lines-brake-fluid-recommentations.html
They can rot from the inside out and can fail in such a way that they become a check valve.

Thanks, folks!

So I'll try releasing the pressure at the MC and seeing if that works this weekend. I'll give an update then.