no rear brakes on 300E
 

Having just replace the rear rotors I now have evidence that the rear brakes are doing almost nothing. 250 miles and still have tooling finish. Previously I have replaced the brake fluid, DOT 4 BMW stuff from my mechanic, new pads and I have taken apart the calipers and meticulously cleaned them. I also polished the pistons with 1000 grit wet paper, very lightly. When I replaced the rotors last weekend the pistons retracted very easily in the caliper and there is no evidence of leakage.
What next? I don't think at this stage new calipers will help although the seal in the calipers did seem very hard and the rubber boots are in poor shape. Is there a repair kit? Is there an adjustment for front/rear balance? I have a firm brake peddle with no loss of pressure or spongy feel when stopped.

Thanks in advance.

Todd
1988 300E
Arctic White 81k miles

When was the last time you replaced brake fluid? What is the condition of the hoses at the calipers? You can also ck it out by raising the rear wheels with the car in neutral have someone mash the brake pedal and see if the brakes are really working or not.

Jim,

I changed the fluid in July. The hoses look ok, they're not cracked or weather checked anyway. I'll raise a wheel up tonight and do that check. Should I be looking for flexing in the hose when the brakes are applied too?

Todd

The hose will not move. I was wondering about pluggage in the hose. Did you get good flow out of the hoses at the rear wheels when you changed it? Also, another thought would be that you may need to re-bleed them to insure you do not have any air in the system. Keep in mind that the braking action at the rear is a fraction to what it is at the front wheels.

Jack up both rear wheels. If you have an and put in gear. Then step on brake pedal and then the accelerator. If you have an auto trans, you should be able to keep the wheels from rotating with full power applied. The torque converter will just slip. If you have a manual trans you will have to rotate the wheels in gear first and then apply the brake. You should be able to stall the engine even when applying about quarter throttle.

I just ran the tests. With both wheels off the ground and the engine not running I could not turn either wheel with the brake applied. I then started the motor and gassed it and applied the brake. I could get one or both wheels to spin then the peddle would drop down but not to the floor till the abs would start to pulse. I did this several times but didn't try full throttle as I had done this test before reading the last post. I never did completely stop the wheels though. I am planning on bleeding the back brakes again this weekend. I inspected the brake lines and they look ok and don't flex when brakes applied. Any ideas??????

Thanks
Todd

After only 250 miles I don't think you'll see much wear if any. remember most of your braking action is done at the front wheels. Thats why you replace the fronts more often than the rears.

If the the brakes stopped the rear wheels enough to trigger the ABS, the brakes must be working properly. With ABS you shouldn't be able to stop the wheels completely. That is the way ABS is supposed to work. ~P E H~