V8 caliper splitting - straightforward!

nonote

Member
First off apologies if this has been covered elsewhere in the forum, I can't see it anywhere.

Anyway, I recently had cause to give my left front caliper some attention as it was leaking fluid. Once it was off it was a straightforward clean up of the (previously fitted stainless steel) pistons and replacement of the rubber components, the outer cover on the "two piston side" had hardened over time and allowed dirt where it shouldn't be.

This then prompted me to sort out my stash of old scrapyard pistons to make them ready for service replacements in the future.

First issue is to get the pistons out. There was no possibility of levering them out gently with a couple of screwdrivers, they were firmly stuck in. One recommendation in this case is to use a grease gun connected to the caliper to force them out. Easier said than done as the saying goes! First of all locate a lever operated grease gun then, in my case, get the thing filled and then get it to work! Next problem is how to connect it to the caliper. Scour the internet for a grease nipple with the same thread as the brake hose. I used a 3/8 straight nipple. This could do with having a bit longer threaded part but I couldn't find one. The reason for this is that the threads on the caliper start a few mm below the surface and only allow a couple of threads to hold the nipple. Anyhow it worked!

Except for the small pistons in one caliper.

Not sure how a specialist would do it but I split the caliper to allow access and used a combination of bench vice, mole grips and small stilsons to finally shift them. Damaging the pistons is not an issue, if they are really stuck you will need to replace them anyway.

Every workshop manual I have ever used over the years tells you NOT to split the calipers with no explanation of why you shouldn't. I believe the only reason is because most calipers have flexible sealing washers (the little black round things in pic 1) around the fluid passages between the two halves and these have never been available to the public. I suppose it's to stop unsupervised/untrained folks making a hash of of their brakes (possibly by using unsuitable 0 rings) and the resultant consequences. They fit into a machined recess so replacing them is quite straightforward. Some repair kits now come with these included and some suppliers offer them as separate items.

The pictures show the mess the calipers are in, what you can't see is the crud that was blocking the fluid passages, even the pressure from the grease gun wouldn't shift it. An electricians screwdriver eventually dislodged it. Based on what I've found in this caliper I would always consider it necessary to split a caliper during overhaul in order to clean it properly.

The picture of the bolts includes the possible size of socket needed to undo them, however, in my case the heads were so crudded up I hammered the nearest best fit metric impact socket onto them and it worked, the bolts are scrap anyway. These bolts need to be torqued to a very high figure and they need to be of the correct specification.

Do your own research re specs and torque figures, I don't have access to the makers specs, so won't quote what I'm using, I just go by what I can find on the internet tempered with a little common sense to filter out the rubbish!

Just as an aside these v8 calipers were used on other vehicles, these include:

E type Jaguar series 2

XJ6 Jaguar early

Austin 1800 S , the sports version not the standard car.

Lotus some models of the era.

There is also a similar looking caliper which will fit but which uses smaller diameter pistons so beware if you pick one of these up at an autojumble or the like. The repair kits for the E type and the Rover 3500 seem to be identical yet for some reason the E type kit can be cheaper from the same supplier, guess which one I'm ordering!

Hope some other members can offer accurate information regarding rebuild torques and other stuff.
 

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hELPFUL, THANKS. I have seen the seals between the halves for sale a while ago, so they are available.
 
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