26 replies to this topic

[Daniel_moody25]

Hi there I've got a set of 8.4 standard calpiers I'm rebuild after being shot blasted. I've used grease to remove the pistons so plan on cleaning them out with parts washer. Will I need to split them and replace the inner seal?

[carbon]

Used grease to remove the pistons?

 

How?

[Daniel_moody25]

3/8" grease nipple where hose goes and then just pump grease in til pisto nd come out

[Ben_O]

As far as i know, you only need to remove the o ring IF you split them.

 

I did read that you should only split them and reassemble in a controlled area to avoid contamination. I however split mine before reading that but would be interested to hear other views on it.

 

Mine are scrap anyway as there was lots of pitting and corrosion on the mating surfaces.

[Spider]

Hi there I've got a set of 8.4 standard calpiers I'm rebuild after being shot blasted. I've used grease to remove the pistons so plan on cleaning them out with parts washer. Will I need to split them and replace the inner seal?

 

Yes. Greases and Oils are not in any way compatable with Rubber Brake Parts.

 

Split them, clean them in degreaser, then again several times with Metho, then finish off with Brake Cleaner.

 

There is (specific) Rubber Grease available, which you can use for re-assembly, or just use Brake Fluid. I use the Rubber Grease because I can't stand Brake Fluid being on my hands! The Rubber Grease don't knock paint work around either.

[Daniel_moody25]

Hi there I've got a set of 8.4 standard calpiers I'm rebuild after being shot blasted. I've used grease to remove the pistons so plan on cleaning them out with parts washer. Will I need to split them and replace the inner seal?

 
Yes. Greases and Oils are not in any way compatable with Rubber Brake Parts.
 
Split them, clean them in degreaser, then again several times with Metho, then finish off with Brake Cleaner.
 
There is (specific) Rubber Grease available, which you can use for re-assembly, or just use Brake Fluid. I use the Rubber Grease because I can't stand Brake Fluid being on my hands! The Rubber Grease don't knock paint work around either.

Okay thanks for the advise, how many seals per caliper is it, for the inside that is cause I have the rebuild kits

[Spider]

 

 

Hi there I've got a set of 8.4 standard calpiers I'm rebuild after being shot blasted. I've used grease to remove the pistons so plan on cleaning them out with parts washer. Will I need to split them and replace the inner seal?

 
Yes. Greases and Oils are not in any way compatable with Rubber Brake Parts.
 
Split them, clean them in degreaser, then again several times with Metho, then finish off with Brake Cleaner.
 
There is (specific) Rubber Grease available, which you can use for re-assembly, or just use Brake Fluid. I use the Rubber Grease because I can't stand Brake Fluid being on my hands! The Rubber Grease don't knock paint work around either.

Okay thanks for the advise, how many seals per caliper is it, for the inside that is cause I have the rebuild kits

 

 

Generally the seals come as a kit and one kit does one caliper, but check with the supplier. NOTE though that none of the kits (that I have ever bought) come with the Bridge Seal, that's the flat one that goes between the two halves. If you've got 4 Spot Calipers, most have 2 bridge seals. As you've pressed the pistons out with grease, I would recommend that these also be replaced no matter how clean you have gotten them.

 

The seals for each piston consist of 2 seals, one being the Pressure Seal, the other being a dust wiper. The dust wiper is held in place with a pressed steel retainer, a bit like a ring with a return on it. These usually come with the Seal Kits. Take your time fitting these back in as they are easy to distort. I usually knock them in in one go by placing a nice clean flat piece of hard wood over them and then giving that a decent tap with a hammer.

[Daniel_moody25]

Hi there I've got a set of 8.4 standard calpiers I'm rebuild after being shot blasted. I've used grease to remove the pistons so plan on cleaning them out with parts washer. Will I need to split them and replace the inner seal?

 
Yes. Greases and Oils are not in any way compatable with Rubber Brake Parts.
 
Split them, clean them in degreaser, then again several times with Metho, then finish off with Brake Cleaner.
 
There is (specific) Rubber Grease available, which you can use for re-assembly, or just use Brake Fluid. I use the Rubber Grease because I can't stand Brake Fluid being on my hands! The Rubber Grease don't knock paint work around either.

Okay thanks for the advise, how many seals per caliper is it, for the inside that is cause I have the rebuild kits

 
Generally the seals come as a kit and one kit does one caliper, but check with the supplier. NOTE though that none of the kits (that I have ever bought) come with the Bridge Seal, that's the flat one that goes between the two halves. If you've got 4 Spot Calipers, most have 2 bridge seals. As you've pressed the pistons out with grease, I would recommend that these also be replaced no matter how clean you have gotten them.
 
The seals for each piston consist of 2 seals, one being the Pressure Seal, the other being a dust wiper. The dust wiper is held in place with a pressed steel retainer, a bit like a ring with a return on it. These usually come with the Seal Kits. Take your time fitting these back in as they are easy to distort. I usually knock them in in one go by placing a nice clean flat piece of hard wood over them and then giving that a decent tap with a hammer.

Again greate advise thanks. Do you know weather there is a torque setting for the bolts that hold the two halfs together or is it just a case of getting them as tight as I can and maybe put some loctite on them?

[Spider]

I've never found any BMC / Leyland / Rover published figures for these, however in cases like this, I work from Fastener Charts. The Torque that i use is 70 ft / lbs DRY.

[Daniel_moody25]

Okay then thanks

[Steve220]

That isn't a grease nipple, that's the bleed valve.

[Daniel_moody25]

Nope I bought a grease nipple to use just for this

[dklawson]

That isn't a grease nipple, that's the bleed valve.

 

With the grease extraction method you remove the bleed nipple and replace it with a 3/8-UNF Zerk fitting.  Pumping the calipers with grease then forces the pistons out since a grease gun can develop a tremendous amount of pressure compared to an air compressor.

 

Personally... if the pistons are stuck that bad I will use water pump pliers and/or pipe wrenches to twist them loose and muscle them out.  The pistons will be ruined but when stuck that badly they need replacing anyway.

[Daniel_moody25]

That isn't a grease nipple, that's the bleed valve.

 
With the grease extraction method you remove the bleed nipple and replace it with a 3/8-UNF Zerk fitting.  Pumping the calipers with grease then forces the pistons out since a grease gun can develop a tremendous amount of pressure compared to an air compressor.
 
Personally... if the pistons are stuck that bad I will use water pump pliers and/or pipe wrenches to twist them loose and muscle them out.  The pistons will be ruined but when stuck that badly they need replacing anyway.

Well I didn't take the bleeder out I left it in and put the zurk on the flexi fitting as there same thread. I didn't do it this way cause they were stuck it's just I don't have an air compressor so was the easiest method seen as I wasn't going to take the ones already on the car off to used brake fluid to do it with

[Icey]

With the grease extraction method you remove the bleed nipple and replace it with a 3/8-UNF Zerk fitting.  Pumping the calipers with grease then forces the pistons out since a grease gun can develop a tremendous amount of pressure compared to an air compressor.

 

This is a new one on me, in all the years of working on cars I've never heard of/seen someone using a grease gun to do this. It seems like such a bad idea, getting the grease out of the callipers must be a nightmare to the point I'd want to just chuck them in for refurb units!

 

Usually it's either pushing the pistons out while the callipers are still on the car or using something (wrench/clamps/pliers of some kind) to extract the pistons if the callipers are already off. I've just done this myself with the Metro 4-pots we have (both ways actually - I forgot for the first calliper and hand to make a sealed brake line fitting to be able to pressure the system for the other side).