Hi Friends recently i had very weak rear brakes and after some inspection i found that i have a stuck rear right brake caliper so what i did is i took a part the cylinders that pushes the pads for the right side and also the left cleaned them with wd40 and put all things back
and now i have this spongy brake pedal that goes to the floor
im sure there is no air in the system
so to day i took my car to a mechanic and he told me that i need to replace my 2years old brake pump
please my friends help me i cant drive my car with this pathetic weak brakes

Hello,

First, WD40 is a solvent not a lubricant. Good for getting rust off thing but certainly not for lube.

Why is a brake pump? Mine has a master cylinder, but I am no expert here either.

Did the mechanic show you what needed to be replaced?

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thanks for your replie
i think brake pump and master cylinder are the same thing hhh maybe im wrong
my car is a mercedes w201 2.5 Diesel with the legendary OM602 NA
i dont trust mechanics
the destruction i did with wd40 is for the rear calpers not to the master cylinder so why change it if it has a 2 years old

With ABS brakes, there IS a pump. The ABS pump. It is not the master cylinder. The ABS pump along with the electronics and wheel sensors apply braking to the wheels that need it.

The ABS pump needs bleeding too. You first bleed from master cylinder to ABS pump. You crack the pump connections one at a time with pressure bleeder connected and wait until there are no bubbles. Then move on to the next one. Then from pump to wheels in usual way. Again you need to use a pressure bleeder. 20psi applied at brake fluid reservoir will do it. You need pressure to force the fluid through the pump. You can buy pressure bleeders or make one yourself.

If you try and bleed by pumping the pedal, you need to close the bleeder screw every time your assistant lets off of the pedal. Otherwise air gets sucked through the bleeder threads. You also need to keep the reservoir filled - even with the pressure bleeder.

__________________
Graham
85 300D,72 350SL, 98 E320, Outback 2.5

thanks my friend
i already solved my problem using a slightly similar method
thanks all

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1991 190D 2.5 515K

It is possible you damaged the master when pumping the brakes to the floor. Brake parts on old cars probably should be replaced when no longer working, unless you are an expert in hydraulic systems.

I assume that you popped out the pistons, cleaned out any rust and then reinstalled the pistons. Did you put in new seals or did you use the old seals? You should have used new seals because that may be your leak.

Suggest you bleed the brakes all around again. Be sure to take the cap off the master cylinder and keep it full of fluid when you bleed. There should be no spongy feeling. Start with the rear, probably right - the caliper farthest away from the master cylinder.

Also I am not sure but your master cylinder may (like mine) have two compartments for fluid and I understand that it is hard to get fluid topped up in the rear compartment of the master cylinder. You might check.

x2. Also start with the wheel furthest from the master cyl.

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

+1
There's still air in the system. The fluid reservoir has two compartments, one for the fronts and one for the backs. In order to fill the rear compartment, the front has to overflow. The surest way to accomplish this is to fill the reservoir all the way to the brim, then bleed the brakes keeping the reservoir topped up. Once you are sure the system is fully bled, pump the fluid level down to the line.

so my friends if i bleed all 4 brake calipers then the problem is from the master cylinder ?

You mention you tool the seals off of the Pistons in one of the calipers correct? If so, did you replace with new seals and are you sure they are not leaking?

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As long as you bleed them correctly and in the correct order.

Two ways to bleed correctly:
1. purchase and utilize one man bleed bleeder screws.
2. Use the two man (person) method. (I have actually used the Mrs. for this duty).
a. make sure the mc is full in the front and rear compartment. the rear compartment is hard to see without placing your eyes so you can look at a low angle.
b. Starting with the wheel furthest from the Mc, have your helper pump the brakes until there is some resistance in the pumping action. Then have them hold the pedal down while you open your bleed valve and let out fluid until it stops coming out. Tighten the bleed and then let your helper release the pedal.

Good luck!


c. Repeat until you get no bubbles and you have a nice firm pedal.

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Take a look at the link below if you need a helpful guide to address the calipers.

Mercedes-Benz 190 W201 (1984-1993) Technical Articles - Pelican Parts

when i was with my mechanic he had open the abs brake lines so the air has entred the rear brake system and with the help of a friend i bleed the rear brakes for 2hours with no result just air with some fluid that came of the bleeder so i gave up
is that normal or is that a symptom of a bad mc
and whats better buying a brand new or a mc from junk yard ?
because the mc i have is a 2years old and it was a brand new one

That question was answered. You have to keep the reservoir filled to the brim while you bleed the rear brakes.