Rebuild or Replace calipers?

Hello folks -

While I am still not 100% sure I’ll actually restore this car, I am continuing to “tinker”, and so I’d like your thoughts on the brakes.

When I bought the car, I was told the brakes had been rebuilt, and to some degree that looks like a “maybe”. Some lines look newer, there are old brake caliper parts in a box and the vacuum canister and vacuum servo had been removed (Don’t ask why, I have absolutely no idea why that would be a good idea - the brakes were virtually unusable). All this tells me that someone certainly did something to the brakes, and crazy or not, the lines were plumbed well to bypass the missing servo. That said, a power brake system that’s missing its “power” is very hard to use and this was not at all a road-worthy condition.

I replaced the servo and the vacuum canister, everything seemed to work - in fact I’d say the brakes were outstanding…for about a month. I then noticed a leak in the rear passenger side caliper, followed by a leak in the front driver’s side, and at this point most of the brake fluid has leaked out and the brakes were understandably soft beforehand.

So my question is this - do I replace the seals on the calipers, or just get new calipers? When I did this last on my '65, I went with Coopercraft brakes, but that’s a spendy option. That said, I am not into doing the job twice, so can anyone speak to their successes or challenges in replacing caliper seals? Better to just bite the bullet and get four new calipers?



Just replacing seals may not fix your problems. If the wheel cylinders are pitted, you also need to get them repaired, i.e. sleeved. May add a few weeks and a couple hundred $ to your project. Check for prices from Apple Hydraulics or others. My brass sleeves have lasted for 25 years. If you really want to make everything look new, get the calipers and cylinders cad plated before sending off for sleeves.

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Depending on the style of caliper it may be that the pistons are pitted which would lead to leaking. New seals and pistons may be all thats required.

Hard to say , but if you say they was outstanding for about a month , could be just the seals , as pitting takes years .
Then again if the car just sat for that month , if the cylinders are pitted it may not show up
Only way to find out is strip them down and have a look , then decide what way to go

Well, the seals seemed just fine until I reinstalled the vacuum servo / vacuum booster - that’s when they started leaking. I moved the car around once in a while, but not over 5mph because the brakes were really hard to use without vacuum assist - but they didn’t leak. Now, they have vacuum assist but at least two calipers have lost their ability to keep a seal. My initial thought was the extra pressure was just too much for perhaps old seals. I guess its just going to be a strip down and take a look. Is pitting in the cylinders somewhat obvious? I’ve never rebuilt a caliper.

Yes it will be obvious , if car has been standing a long time seals may have just dried out a little
Well worth trying new seals first , you can get away with a little pitting .
As the calipers are connected , remove it from the upright , take the pads out , place a spanner where the disc was and pump the foot pedal , that will pump the pistons out the cylinders ,
I use a foot pump on the bench , if that don’t work . I have a old MOTERCYCLE brake cylinder , sometimes they can be a pig to get out

Why does it matter if the cylinders are not perfect? My understanding is that the seal is made with the smooth piston and rubber seal. If the land for the seal is OK then the condition of the cylinder below that seal should not matter (within limits). I have recovered brake calipers that had seized and rusted pistons. Bead blasted the caliper and then fitted new pistons and seals with excellent results. All in a home workshop.

I’d definitely try new seals - a cheap fix.

if you do decide to replace the cylinders be careful to buy good ones. When I got my Daimler 2 years ago I had to renew the pads and the cylinder which had recently been replaced by the previous owner, all shiny and new, was seized solid while all the other old & dull & dirty ones were fine

It depends on the type of caliper the OP has some have the seals on the piston which of course will require a good bore to ride in.

Can you tell us what the car is? If it’s an early model, it will have cylinders which must have smooth walls (no pitting) - since the pistons on these carry the seals, the piston surfaces don’t matter. Later models have cylinders that carry the seals, so the pistons must be smooth. These are easier to rebuild, because you can buy new pistons and don’t have to send the caliper away for sleeving. If you post photos of the calipers, there is a better chance you can get specific help on this forum. It sounds like you have the skills to do the job, either way. You will have to tear the calipers down to know what is wrong. My guess is that whoever rebuilt the calipers last, didn’t sleeve or replace pistons (whichever was appropriate) and the new seals were cut by pits during your first month of use. Do the job right and it will last a very long time with regular brake fluid changes.

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Hi all, thanks for the replies.

The car is a 1961 MKII, and early '61 if I recall. That said, I do not know what calipers it has, whether originals, something from a later MK2, or something aftermarket from the usuals. I’ll see if I can grab a few pictures and post them.


If they are original spec units they should be Dunlop with 31/8 inch stamped on the outer removable cylinder IIRC. Not sure of rears but 1 7/8 inch again IIRC.

If u intend to keep the car long term I would bite the bullet and re sleeve in stainless. Lasts forever but brass is cheaper but abrades the seals over time depending on time and mileage…

But really you should remove all cylinders and dis-assemble and see what’s what before u do anything.

If you want better breaking upgrade the front brakes but this is $$$. A potential cheaper option if obtain Volvo 144 I think front calipers(made by Dunlop or Girling ? )and how to modify them for your car is somewhere in the Archives. Braking is SOOOO important it’s best not the cut corners

Good luck


My Daimler V8-250 is a 1968 model so will possibly have different brakes to your car but I was most impressed with my brakes when I had to do an emergency stop to avoid a dickhead farmer in the biggest tractor you’ve ever seen on the wrong side of the road heading straight for me without a care in the world.

So if your brakes can be made to work properly I don’t see any point in ‘improving’ them. Apart from having ABS, you won’t get anything any better.

For the month the brakes worked without leaks, I’d have put them among the best “old car” brakes I’d used, but then the seals started to leak.

The weather hasn’t been great and I’m not overly motivated to go out there and start tearing off calipers, but more and more I suspect I’ll go with new units.

There are days where I feel like its worth restoring, and other days where I want to just cut it loose and move on.

For the common calipers, such as the Dunlop that would have come stock on your car, the rebuilders (such as Apple Hydraulics – no affiliation to me) usually have them on the shelf already sleeved and ready to send, so that you could save yourself some down time that way, but you will have to have a closer look at your car to be sure which calipers you have. Sleeving should be about $70 x 2 per caliper (brass) plus the cost of the kit or $100 rebuilt for each caliper half. All in all, that is a little less than new steel caliper 1/2s, and quite a bit less than stainless caliper 1/2s, so I usually just sleeve them. I’ve had no issues with brass sleeves. If your rotors and pads are ok, it’s just a day’s work.