Rear brake questions for 92 190E
 

Hi Gang,

I just replaced the front pads on my 190E. No problems!

I have some questions on the rear pad replacement.

1. How do you fill the rear axle portion of the master cylinder?
2. How do you pull the rear pads out? I pulled the caliper off the mounting bracket without problem but there seems to be two rods that have a threaded end but no aparent grip on the other end.
3. Do you need a special tool to retract the rear caliper pistons? Are the pistons threaded?

Thanks,

Unless MB did something while I wasn't looking, those are ATE calipers back there. Use a 1/8" drift (or a large nail) to drive the pins back toward the center of the car, no need to remove the calipers unless you need to replace the seals (rebuild). Pins are a "tap" fit. The antirattle spring will snap up when you take the first one out.

Push the pads back a bit and they should pull right out. Note that if they have been pressed right up on the antirattle spring, the pistons will be stuck and you MUST rebuild the calipers (an easy job) or they will drag terribly and may even leak. You can free them up (after wrestling the pads out) by CAREFULLY stepping on the brake pedal until the piston comes free, but if you pop it out of the bore, you will have to rebuild (they always leak if you don't).

If the pistons press back easily, just drop new pads in AFTER using a small wire brush to clean ALL the rust and corrosion out of the pad slot. Put a small amount of antiseize (a.k.a MB brake pad paste) on the side of the backing plate where the touch the sides of the slot and some on the back of the pad where the piston touches - this prevents squealing. None on the pad material itself, please!

Put a bit of antiseize on the contact points of the antirattle spring, put it in place, and push one pin back in through the 'ears' on the pads. Tap home from the back with a hammer, then push the spring down and install the other pin.

Just about the easiest pad change I've ever seen (except that ALL of my MB's have required rebuilds the first time I replaced the pads).

If there is a distinct lip on the rotors, replace them, they are worn out.

Peter

As Peter says its real easy you don't even have to take off the caliper. Just remove the pins that are held in by friction more than anything, take out the metal retainer and slide the pads out with the caliper still on! :)

Thanks!!

Change ONE REAR PAD AT A TIME. If you pull both pads and attempt to push a piston back, the opposite piston could pop out! This caliper design is known as "fixed caliper" - the caliper is solidly bolted to the upright and has a piston on both sides. The more common "floating caliper" design is used up front with a piston on one side and the caliper mounted on bushings to allow it to slide sideways.

Remove one pad, push the piston back, install the new pad, then do the other side of the caliper. The easiest way to push the pad back is to attach a hose to the bleeder valve routed to a container and open the valve while you push the piston back, which will push the excess fluid through the the valve and into the container rather than pushing it back into the reservoir, which could overflow if it is already full.

The reservoir has internal baffling that separates the front and rear reservoirs. In order to fill both, you need to fill to the top and then wiggle the reservoir back and forth sideways.

Look at the level on the RH side (as referenced from the point of view of the driver) of the reservoir to determine its level. This is the "hidden resevoir" (tough to see) that I think services the rear.

Duke

This is not usually recommended since you should not have to top up the brake fluid reservoir if all components are working. by opening the system at the back end (esp. if experience is an issue) there is the potential for one to accidentally introduce air into the lines requiring a brake system bleed.

if brake fluid overflow @ the reservoir is a concern, some rags and a dedicated syringe or bulb style baster is easier than fiddling with the bleed valve.

It's a lot easier to do the job at one point on the car. I've never had a problem introducing air into the system and the pad change takes about two minutes per side.

Duke