TR4/4A TR4 Brake Caliper Re-Assembly

[doughairfield]

Hello,
I am putting new pistons and seals in the calipers on my 64 TR4 as the old ones were rusted and pretty well shot. The workshop manual doesn't mention it, but is there any need for assembly lube when putting the new pistons into the brake calipers? I coated the insides of the calipers and outside of the pistons with brake fluid but am now thinking a silicon lube might be a plus to keep water out and allow the pistons to move easier.

 

[sail]

I only use brake fluid.

 

[Brosky]

That's all you want to use on your brakes, which is a sealed system.

 

[trrdster2000]

Doug, if you have some of the red grease from Lockheed or Girling, I would add a thin coat on the pistons and the walls. Most will scrap off when you insert the piston, but enough remains to help sealing.

Wayne

 

[karls59tr]

I'll be doing my calipers soon and was wondering if you had any difficulty getting the pistons out of the calipers? Did you take the calipers off and soak everything in PB Blaster or were the calipers still on the car so you could use the hydraulics by means of the brake pedal to force the pistons out? Karl 67 TR4A IRS

 

[sail]

Using the hydraulics while still on the car would seem the simplest. Mine were off the car and had sat for years. I clamped a bicycle foot pump hose on the bleeder and blew them out. You need to have both in part way to keep pressure. Once one was loose I held it part of the way in with a board and clamps to the workbench allowing the second room to come loose.

 

[smading]

Getting pistons out is a piece of cake using the method described in this moss post. https://www.mossmotors.com/forum/forums/thread/10530.aspx I used a 1.5" plumbers plug and friction tape I picked up at Home Depot. Took me about 10 minutes to get all 4 pistons out of my type A TR3 calipers.

 

[JerryVV]

Occasionally I do dumb things. Keep you hand out from between the pistons if you are using air to get them out. It really hurts, and I mean really hurts for a long time if you have your hand between the pistons. You can guess the rest.

 

[alanjohnturner]

This is an early design of caliper and not much thought was given to easy assembly.

If piston-seals are the type with a SQUARE cross-section then its vital to get the groove in the piston COMPLETELY clean right into the corners.

If you dont do this the seal wont go to the bottom and you will chop a bit off when you push it into the piston.

If you are lucky you will spot a chip of rubber and do it again. If you dont spot it then there may be worse to come.

Getting the piston back in without spoiling these seals is the main difficulty in rebuilding these calipers.

There are two types of dust-covers. You probably have the type that sits in a very narrow groove right at the top of the piston.
Dont think you can put these in after you have fiited the piston. They wont go.

You have to put the dust-seal into the caliper body and then push the piston through the central hole.
This makes getting the pistons in much harder.

Unless you are a really good mechanic I'd consider shipping calipers of this type to a specialist.

Al.

 

[Geo Hahn]

...There are two types of dust-covers. You probably have the type that sits in a very narrow groove right at the top of the piston.
Dont think you can put these in after you have fiited the piston. They wont go.

You have to put the dust-seal into the caliper body and then push the piston through the central hole.
This makes getting the pistons in much harder...

Getting the dust seal to swallow the piston is pretty easy if you rig up some air pressure to the caliper. With the opposite side blocked and the piston perched on top of the seal some low air pressure will cause the seal to inflate and try to get around the piston. Just help it do that (wiggling the piston is often enough) and Walla! the seal will pop on and the piston should slide home w/o further ado. Once you get the hang of it those dust seals pop on in seconds. Of course, once you get the hang of it you're done for another 10 years.