What's this caliper part for, and do I really need it?

The rebuilt front calipers that I just purchased didn't come with this part, so I am wondering if I really need one. The rear calipers didn't have them either... The Chiltons repair manual I have also doesn't give much detail on things either...

[Aaron]

That's a dust cover which snaps in over the boot over the piston. Do you need it? Well some calipers (most I ever recall seeing, actually) have them. Don't know who did the rebuilds on yours but I would question them!

So does that mean I should take my calipers back off, and try and snapping the dust covers on. I tried earlier today, and had no luck.

When I took my core back to the parts store, I asked the manager about them, and he said he had no clue what they were for, and he said he wasn't sure if the rebuilds were supposed to have them or not.

I have a new question about shims, how exactly do they work? I know them because the calipers aren't alligned correctly.

They are seals that go over the piston to keep the rubber boot intact. When I last did my pads, they came off along with a rubber boot seal. I had to replace my front calipers because dirt and water got in there and siezed the piston. I think they are essential to keep the piston free of dirt, and siezure.

[leathermang]

"I think they are essential to keep the piston free of dirt, and siezure."---turbodiesel
Very True !

So how exactly do I get the dust cover back on? There must be a trick that I don't know about... When I changed the pads on the rear brakes, I noticed that the rear calipers didn't have the dust cover. Should I try and get some for the rear calipers too?

I think your only option is to rebuild the caliper yourself, or plan on getting rebuilt calipers to go along with your next set of brake pads. Those metal discs are pressed into place on the piston and it's a very precise fit, if that disc is bent at all you have no shot at all of getting it back on. I tried to get mine back on with no luck.

OK, I just won't worry about it then, because I probally won't have the car anymore by the time I need new pads. The next owner of the car can worry about it...

Now all I have to worry about is getting the caliper alligned so that it won't rub up again the Hub?, I don't know what to call it...

[Ken300D]

I can't get those things on for anything. There must be some kind of special tool involved. They are very lightweight metal, easy to bend, and they are pressed on.

Impossible !!!!

Later calipers (like a 1987 300D) have the same type of heat shield, but it CLIPS on instead of pressing on. Simple.

So, on the caliper I rebuilt on the 1985 300D (rear) doesn't have this thing now. I still think the rubber boot is sufficient to keep out dust, and that this is something for heat.

Ken300D

[psfred]

That is a heat shield, and yes, you should have it in place.

I put mine in with a piece of wood -- put caliper on floor, align shield with the "notch" in the rim on the piston (hint -- this is a good way to make sure the piston in in the bore at the correct angle), then stick the board through the caliper and press the heat shield into the piston. Make SURE it's right, as it won't come back out intact.....

It protects the rubber piston boot from the heat radiating from the backing plate of the pad.

If the caliper is rubbing on the hub, you probably have the wrong caliper, it should not touch, only the pads should contact the rotor. Some older models used shims to align the caliper with the rotor, but even with them missing, I cannot imagine how the caliper could contact the hub or rotor if everything is installed corretlys.

Peter

The part that is rubbing is a little plastic piece, and it is hardly touching. I think I know how to get it in place so that it won't rub. Tomorrow I will try it, after I pull the calipers off again and try and put the heat shields back on. After that I am going back to the parts store to complain to the manager about the calipers, so he can complain to the company that did the work...

[Beagle]

These heat shields are necessary and serve a dual purpose. Firstly as has been said they protect the rubber boots from being destroyed by radiated heat and red-hot dust swirling around while braking. This dust will actually cause the rubber to ignite during prolonged and severe braking.

Secondly, and just as importantly, they prevent the caliper pistons from rotating thus keeping the relieved 1/3 segment of the piston rim correctly orientated. The inside raised part of the dust cover ( the left hand side on your pic) sits against the inside edge of the brake pad backing-plate preventing turning.

A “G” clamp and an old brake pad works well to press them back into the piston but be sure to keep them square.

Today I pulled the calipers back off and installed the heat shields. They snapped right back on, but I had to have the pistons out some. When I was trying it earlier the pistons were all they way compressed. I think I spent about 3 hours getting everything back together today.

After driving around for a few miles, it seems that brakes might be sticking, but it might also be the fact that I have been driving a g@$$er for the past 3 weeks, while the car has been sitting. Would it be a good idea for me to pull the wheels off and check the brakes after driving the car for a few more days?

[leathermang]

There are special plyers shown in the FSM for installing those things... I think....might want to look at one....

Originally posted by leathermang
There are special plyers shown in the FSM for installing those things... I think....might want to look at one....

I know all about those, I was talking to one of the tool sales people at my local Sears, and this guy is a former MB Mechanic. He told me that Channel Locks with an old Brake pad work good.