Brakes
 

Hi Guys, I need to R/R my brake pads on the front of my 84 300D, is this a big deal, I have a Haynes Manual is it sufficient for guidance. Thanks, John

Sure, Haynes is great for routine maintenance. You might even get away without having to remove the caliper, but it's probably best to remove it and clean everthing up, inspect the rubber boots on the caliper pistons, and apply brake anti-squeal paste to the backs and slider areas. An MB mechanic friend told me he always pulled the edge of the boot out a bit and squirted in a shot of silicone to forestall rust from forming.
You can re-use the wear indicators (if you don't have access to a dealer or don't want to wait) if they're not worn too far by dabbing the ends with silicone RV sealant to re-insulate them before inserting again.
Be careful pushing the pistons back to make room for the pads. Go slowly so as not to disturb the master cylinder cups.
Always use lock-tight on the old caliper mounting bolts.

You will only need to remove the calipers if the rotors need replacing or the pistons are stiff going back. The latter means caliper rebuild time, they will drag and/or leak of the seal is bad.

If the rotors have a distinct lip on the outer edge, replace them.

The Haynes manual is adequate for this job, although barely.

If you are only replacing the pads (good rotors -- if in doubt, replace the rotors, too, the trouble you will get if they are too thin isn't worth not doing this!), clean the slots they fit in completely. Rust in the "corners' will cause the pads to stick and squeal like crasy, and can cause the brakes to drag.

Coat the back of the pad with antisieze where the piston contact it, and put some on the edges of the backing plate ONLY on the sides where it will contact the caliper slot. NONE on the friction material, please! This will go a long way to prevent squeals.

Check the condition of the dust boots on the piston -- cracks, tears, or signs or excessive stiffness mean a caliper rebuild before the piston gets stuck.

When pressing the pistons back, remove the fill cap on the fluid reservoir, else the won't move -- there is a very small bleed hole in the cap! If they won't move back easily with a small C-clamp or wooden lever, rebuild the caliper, they have cocked in the bore or are dirty, and will sieze shortly.

If the backing plate on the pads has touched the spring over the pads, it's also rebuild time, the rotor was run too thin and the piston seals are shot.

At the age of this car, you should really expect the calipers to need a rebuild (19 years is a long time!). It's not hard -- do a search. Should be covered by the haynes manual anyway.

Peter

I would also replace all 4 brake lines, I did them on my SDL and they were starting to crack. for $50 for all of them it isn't worth having old ones. Also the brake fluid should be flushed every other year.