1982 240d rear brake problem
 

I recently bought a 240d with a lot of delayed maintenance. At least one rear brake was not working. I replaced both rear calipers, pads and bled them quite a bit two different times. Pumping the brakes sends brake fluid out the bleeder however apparently not enough to lock up the brakes. What should I do next? Master cylinder?

You should flush the system with a bottle or two of fresh fluid first. Then, the MC.

How well does the car stop?

Yes, the brakes won't lock up when bleeding.
Good on the replacing calipers, test drive, and compare to previous brake feel, stopping power.

I don't understand your problem. when bleeding them why would you try to lock them up. I think maybe you are not bleeding them correctly. In any case if you have a good firm brake pedal you are fine.

Tom W

I think he means they are receiving fluid while bleeding but they are not getting any pressure to stop the wheels when he is not bleeding them.

This can happen if the master cylinder runs out of fluid while bleeding, and you can get an air bubble. Might need to pull the lines at the MC and "bench bleed" the master.

Jim

I will bleed the brakes some more this evening
 

The problem is that once I am done bleeding the brakes the rear brakes still do not work. I have the 240D on jack stands and while the engine is running my wife has the brake peddle fully depressed and I can physically turn the rear tires - the rear brake does not lock up. Right after installing the new rear calipers, pads and bleeding the brakes lines I test drove the 240d and while the front brakes continued to work well the rear brakes didn't work at all - this is easy to tell when the roads are icy, the vehicle is stopped and the rear wheels continue to turn on the ice. I will let the brakes lines drip bleed this evening and run some more DOT4 fluid through to make sure there is no air in the system. However if air in the system is not the problem what should I try next?

The brake fluid reservior has a front and rear compartment in it. Sounds like maybe you emptied the compartment for the rear brakes, which I believe is the front compartment. I've done this too. You have to completely fill up the reservior to fill the front compartment. Might check that out. If the reservoir is clean you can see both levels if you look closely.

Reference the new calipers, are the bleeder valves on the top or the bottom?

I have been filling the reservoir
 

It is possible that the reservoir was sucked dry the first time I bleeded the rear brakes after installing the new calipers and pads. However since then I have been very carefull to keep the reservoir (I noticed the split compartments early on) topped off while bleeding the brakes. While the engine was runing, 1. my wife would depress and hold the brake pedal, 2. I would loosen the rear bleed nipple - break fluid would squirt and drip out - and then I would tighten the bleed nipple, 3. my wife would then slowly release the brake pedal. This process was repeaded over and over again on the back and front brakes. In comparison the front brake fluid would squirt out with a lot of force and volume while the rear brake fluid would barely squirt out and mostly dribble out. Once the rear brake bleed nipple is tightened the force transfered through the brake fluid to the calipers/pads is insuffient to lock up the tire, to the the extent that I can physically turn the tire by hand (only a little brake pad resistance) while my wife has the brake pedal fully depressed. I am trying to figure out what is wrong here, either I still have air in the brake lines or something else is wrong. The rear brakes were not working when I picked up the vehicle, so I do not know if it had more problems than just the rear calipers and pads. The front brakes appear to work well.

Sounds like you might need new hoses on the rear. Sometimes they swell internally and restrict flow. Also make sure they are not twisted or kinked. Same with the hard line-check for damage.

Is the pedal firm when the brakes ae applied?

this sounds like you have plugged lines, or damaged flexible lines. I would pull the flex lines and replace them.

I second replacing the soft lines. I did mine when I rebuilt the brakes on my '83. The hoses were like ten bucks apiece at NAPA and only added a few minutes to the total job.

If new hoses followed by a thorough bleed don't help, then it might be master cylinder time.

The bleeders on the ATE rear calipers are on the bottom.
New brake lines have been ordered. The old ones are not kinked.
The brake pedal is firm when pressed. The front brakes work fine.
I allowed each caliper (one at a time) to drip bleed about 20 minutes each last night and I did not test the rear brakes yet.
How should I diagnos a malfunctioning master cylinder?

Alaska,

The bleed screws have to be on the top to get the air out of the calipers. Sounds like U reversed the R and L calipers .

Reverse them again and see if your problem goes away. If problem goes away, hit your self in the head with a hammer so U remember to never do that again. LOL

P E H