Brake Caliper Rebuild Question - PeachParts Mercedes-Benz Forum

RML · #1 01-24-2014, 10:04 PM

I am rebuilding the rear brake calipers on my 84 300D.
They are Bendix calipers.

I cleaned up the metal ring that fits inside the dust boot and seats to the caliper.
I then pulled the new dust boots down around the piston and inserted the piston into the bore.

I have the pads in and operated the caliper with compressed air.
All is good, except the dust boot does not appear to be seating tightly to the caliper where the metal ring is.
I was expecting that it would somehow snap into place but it does not.

I am wondering what will make that seal tight and keep water out.
Should I be using some kind of adhesive or sealant?

.

Stretch · #2 01-26-2014, 04:01 AM

(He says having never seen a Bendix caliper) Are you sure you have the right spare part for it? You haven't got ATE bits by accident have you? I don't know if they are cross compatible or not...

...adhesive or sealant isn't normally needed for this bit. There is caliper grease / paste for the pistons in the bores though...

Clarence Thomas · #3 01-26-2014, 11:43 AM

The dust boots must expand quite a bit to get over the top of a machined ring on the caliper. If you look casually at the caliper, it might not be obvious how much the boot must grow. It's a very frustrating task and usually requires three hands (which, of course, you don't have) to get the boot to expand over the ring on the caliper. Once you do get it, no sealant is required or desired in that area. From memory (a long time ago), the heat shield goes on the top of the piston, not on the caliper.

RML · #4 01-26-2014, 04:28 PM

Quote:

Originally Posted by Stretch

(He says having never seen a Bendix caliper) Are you sure you have the right spare part for it? You haven't got ATE bits by accident have you? I don't know if they are cross compatible or not...

...adhesive or sealant isn't normally needed for this bit. There is caliper grease / paste for the pistons in the bores though...

I do have the correct rebuild kit for my Bendix calipers. And it did not come with a new metal ring to fit to the caliper. So I am using the old one.

Regarding the caliper grease, I thought it was for the back of the pad to prevent squealing. It appears that you are saying a grease can be applied to the pistons and bores. I thought that only brake fluid was supposed to be in that area.

RML · #5 01-26-2014, 04:37 PM

Quote:

Originally Posted by Clarence Thomas

The dust boots must expand quite a bit to get over the top of a machined ring on the caliper. If you look casually at the caliper, it might not be obvious how much the boot must grow. It's a very frustrating task and usually requires three hands (which, of course, you don't have) to get the boot to expand over the ring on the caliper. Once you do get it, no sealant is required or desired in that area. From memory (a long time ago), the heat shield goes on the top of the piston, not on the caliper.

I did find it a bit challenging to get the boot around the ring.

I did resolve the problem. I had painted my calipers and masked off the bore, but got some paint in the channel where the ring goes. I did not think it would make any difference, but that slight change in spec, along with getting a bit of caliper grease in the area, was keeping the ring from seating and wanting to slip out because of the grease. I took a small screwdriver and scraped the paint out, then degreased the area. After that I was able to press the ring into place with the aid of a pliers. It seeems to want to stay in place now.

Stretch · #6 01-26-2014, 04:37 PM

Quote:

Originally Posted by RML

...
Regarding the caliper grease, I thought it was for the back of the pad to prevent squealing. It appears that you are saying a grease can be applied to the pistons and bores. I thought that only brake fluid was supposed to be in that area.

No no no!

I don't want to give that impression at all - different stuff. There is an assembly paste that can be used for the sealing of the pistons in the bores - different from a tiny tiny smidge of anti-seize on the back of the pads to stop them from sticking on the pistons.

Stretch · #7 01-26-2014, 04:38 PM

But anyway this doesn't help with the problem. The dust shield needs to be attached to both the piston and the casing otherwise junk can get in and mess everything up. May be some pictures are in order?

RML · #8 01-26-2014, 04:42 PM

Quote:

Originally Posted by Stretch

But anyway this doesn't help with the problem. The dust shield needs to be attached to both the piston and the casing otherwise junk can get in and mess everything up. May be some pictures are in order?

I did resolve the problem. See my reply in post # 5.

Stretch · #9 01-26-2014, 04:46 PM

Quote:

Originally Posted by RML

I did resolve the problem. See my reply in post # 5.

Oh great stuff (we posted at the same time)

The number of times a newly painted "something" has bit me bit me on the arse...

{but enough of my youthful nights out on the town}