Info on DIY front brakes 1982 300TD

[GlennP]

I have a 1982 MB 300TD wagon. I would like to replace the front brake pads. Is there a technical website that could walk me through the process?

I do all the maintenance on this car, so I am very familiar with it.

Thanks,
Glenn

[ericnguyen]

Dear GlennP:

www.pindelski.com, but that's a subscription fee-based site.

Replacing brake pads on old Mercedes cars is easy. Just follow your common sense and you can get it done without a hitch.

Eric

[psfred]

Here's a set of quick directions:

First, pull the wheel on both sides (safely, please!) and inspect the rotors. If they have a distinct lip or are close to minimun thickness, get new ones. You will damage the calipers and have scary bad brakes eventually if you run new pads on worn out rotors. If the backing plate (steel part) on the pads is very close to the antirattle spring or actually touching it, get new rotors.

If the rotors need to be replaced, get some wheel bearing grease, you have to pull the hub.

Remove the pads from the caliper by driving the retaining pins toward the inside with a thin punch. The large antirattle spring will come loose when you get the first one out. Use a large pair of pliers to pull the "ears" on the pads to remove them, or some stiff wire bent into hooks. You may need to pry the pads back a bit to get them free.

Once you get the pads out, use a small C-clamp or a small prybar to push the pistons back. You will have to remove the cap on the maxter cylinder reservior first! If they do not move back smoothly with minimal pressure, it's rebuild time for the calipers. This is also a DIY job, but more work.

If the rotors are OK for new pads, clean the slot where the pads fit completely of all rust, corrosion, and brake pad dust. If you don't, the pads stick and squeal.

Coat the back side of the backign plaste with antiseize, any brand, or MB antisqueal paste (actually the same thing). Put some one the sides of the backing plate ONLY where it touches the caliper, never on the friction surface.

Instert the pads into the caliper and re-install the antirattle springs and retaining pins. Caot the contact areas of the antirattle spring with antiseize at the points where they touch the pins and the backing plate on the pads.

Repeat for the other side, the PUMP THE BRAKES UP!! I've failed to do this once or twice, It sure gets your attention when your foot hits the floor! Don't move the car until you get a firm pedal.

If the rotors are bad, remove the caliper (two 19 mm bolts) after removing the pads. Use a large pair of channel-locks to pull off the hub cover, unscrew the locking bolt (allen head), then unscrew the hub nut and pull the hub off the spindle. Catch the bearings and put in a clean place. There is usually a grounding clip in the end of the spindle, don't loose it.

The rotor is bolted to the rear of the hub, 10mm Allen key. You will need a large vise to hold the rotor while removing the five screws! Clean the surface of the hub where the rotor mounts, clean the cosmoline off the rotor, and bolt up.

Remove the back bearing and grease seal, clean out all the grease, clean the grease off the bearings with gasoline or brake parts cleaner, air dry (no compressed air!) and repack both bearings. Fill the center cavity up to the lip with grease, leaving a hollow center (takes about 60 gr of grease, the recommended amount).

Place packed rear bearing into the hub and install the new grease seal, then remount hub on spindle. Tighten the nut down until you feel a significant drag on the wheel while turning (this seats the bearings and squeezes out excess grease. Loosen the nut about 1/3-1/2 turn, NOT less than 1/3 turn. You should just be able to move the large washer under the nut with your finger. If you have a dial indicator, set nut for 0.001" clearance. Tighten lock screw, install grounding clip, and re--pack the cap. Install cap by tapping with a large screwdriver and hammer ONLY on the flange. Never drive the dust cap on by pounding on outer end, it causes the cap to distort and actually shrink across the open end, and it will never stay on.

From here, re-install caliper and pads as above.

Some models have a lock plate hammered up around the caliper bolts. If so, drive the "ears" back up to lock the bolts in place. Otherwise, use blue locktite on the bolts.

If the pistons stick badly going back in, do a caliper rebuild, another topic.

Peter