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Brake pistons

keithj
Posts: 6
Joined: Sun Nov 25, 2018 10:29 pm
Location: Mansfield

Brake pistons

Post by keithj » Mon Dec 03, 2018 11:35 am

I have a feeling I will be asking a lot of questions in the near future as I get to know my 1964 v8 better. It has stood for years and although solid is showing signs of neglect. The next problem I have are the brakes. I have managed to check all sets and while the pads are fine I had to remove the piston assemblies to be able to remove and clean them. The problem seems to be that the pistons do not retract as I would expect. I have experience of old Ford calipers which just need "persuasion" from a long bar then press the pedal and repeat. While I tried this it didn't seems to have any effect and I didn't want to be too brutal in case there was damage to be done. The workshop manual refers to a special tool so I guess I was on the right lines. Any suggestions or should I buy some new ones, if so who is a good supplier?

johnwager
Posts: 35
Joined: Thu Feb 11, 2016 3:26 pm
Location: Thundersley, Essex

Re: Brake pistons

Post by johnwager » Mon Dec 03, 2018 12:18 pm

Hi Keith
If your car has been standing for a long period with old fluid in the system the odds are that the pistons and cylinders of the calipers are going to be rusty and pitted.
New ones are easily available from the usual suppliers, David Manners, SNG Barratt etc, for about £85.00 each or there is a company called Past Parts http://www.pastparts.co.uk/index.php?route=common/home who will refurbish your original ones to as new condition. I haven't used them but have heard very good reports.
Ideally you should check the master cylinder and servo as well, as they will probably be in a similar condition :(
It won't be a cheap fix, but with single circuit brakes you need to have the confidence that the braking system is in top condition at all times.
John

Zbigmak
Posts: 13
Joined: Sun Nov 19, 2017 10:45 pm
Location: Warsaw Poland

Re: Brake pistons

Post by Zbigmak » Mon Dec 03, 2018 10:04 pm

I have just rebuilt my brakes and had to replace the pistons and brake seals.
The pistons start to corode and start to bind in the calipers.
Try searching on eBay, they are available or try Barry Thorne who will be able to supply service kits.

keithj
Posts: 6
Joined: Sun Nov 25, 2018 10:29 pm
Location: Mansfield

Re: Brake pistons

Post by keithj » Tue Dec 04, 2018 2:55 pm

Thanks, I think I'll try a bit more brute force and prepare the bank for new cylinders !!

User avatar
captain bobo
Posts: 198
Joined: Tue Feb 09, 2016 7:32 pm
Location: Kimbolton, Cambs

Re: Brake pistons

Post by captain bobo » Tue Dec 04, 2018 8:40 pm

I recently removed my pistons, one of them was leaking a little amount of fluid & caused an MOT failure. I was unable to free up the piston in question, even with a fair degree of brute force. I bought complete piston assemblies from either David Manners or SNG Barratt (I can't remember which) - they were really easy to deal with & re-installation was simple.

Thanks for the link PastParts, I have 2 old piston assemblies that I'll consider sending to them.
Best wishes, Dave B

Ian Hastings
Posts: 75
Joined: Tue Mar 15, 2016 3:00 pm

Re: Brake pistons

Post by Ian Hastings » Wed Dec 05, 2018 12:30 am

There is quite an easy way to remove old rusted in pistons. If you send me a PM with your email address I will send you a description.
Wilf Stephens also had it on his list of advice sheets for the SP.

tjt77
Posts: 408
Joined: Wed Mar 23, 2016 7:01 pm

Re: Brake pistons

Post by tjt77 » Wed Dec 05, 2018 3:30 am

for those with the V8 saloons, if they have been off road for a long period and all the brakes have to be re-done, its worth considering upgrading the front brakes to 4 piston calipers with a kit from SNG Barratt .(i believe made by coopercraft) costs about the same as replacing all the parts in the original calipers.. and is basically more modern and efficient whilst being simpler and longer lasting due to larger pad area etc... As supply has improved in UK . prices have dropped somewhat from where they were a decade or more back..same true with discs.. in the USA if keeping with the original set up, the caliper/piston units can be purchased at lesser cost of repro dunlops by using those sold by Nissan for the 60s fairlady ..basically a direct replacement 2 1/8" improved dunlop made under license by sumitomo.. they generally run about $110 each online..and are better quality than the originals... I send rear calipers out for professional rebuild, as its more economical than replacing them with new UK sourced replacements..(which commonly have the girling logo on them today) always wise to replace flex hoses every 10 yrs or so too.. they often look just fine, but often have collapsed internally and become restricted..

keithj
Posts: 6
Joined: Sun Nov 25, 2018 10:29 pm
Location: Mansfield

Re: Brake pistons

Post by keithj » Sat Dec 08, 2018 2:17 pm

Thanks everyone, I have had another look and tried my general "persuader" (4lb lumpy) and I think I'm best getting some new ones. We are looking at heading to the Pyrenees next year so brakes will be a bit important.

fredeuce
Posts: 20
Joined: Mon Feb 29, 2016 10:56 am
Location: South Australia

Re: Brake pistons

Post by fredeuce » Sun Dec 09, 2018 1:10 am

Brute force is not an ideal way to remove frozen pistons from brake calipers.

In recent times, after attempting various brute force methods I have adapted an oil gun , which is similar in design and construction to a grease gun but has seals that allow the use of oil, for this purpose.

Taking that oil gun and fabricating a few pieces of brake line tubing together an appropriate pipe nut with an adapter to the oil gun. Remove the grease nipple fitting and fit the pipe according to the thread in the caliper. ( I play around with XJ6 Jags and they have both metric and imperial threads) It is then simply a matter of filling the gun with some oil connect to the caliper and start pumping. The watch those pistons start to move. Often I use a clamp to hold the piston that is first to move to enable the others to be moved.

The gun will generate up to 10,000 psi which is more than enough to move the most stubborn of frozen pistons and is performed on the bench with relative ease. This way you can at least salvage the caliper housings and just fit the seal kit and replacement pistons.

Image

tjt77
Posts: 408
Joined: Wed Mar 23, 2016 7:01 pm

Re: Brake pistons

Post by tjt77 » Sun Dec 09, 2018 7:57 pm

reply to fredeuce.. really depends on how one wants to spend ones time:- rebuilding stuck calipers at home is a lost cause..its both messy and potentially dangerous.. I know of one individual who lost an eye when a stuck cylinder grenaded on him when he put high perssure to it.... specialists who do this work soak them in a chemical bath for serval days to remove the corrosion.. and have the machinery to re-line the pitted bores..given the fact that availability of new ones is better than ever in the past.. and that prices have dropped to boot.. re-building at home is not a wise, sensible or practical option.. although it can be an 'educational' experience for those who like that sort of thing.. brakes are such an important aspect of any car.. that is not wise to take any short cuts.. and always sensible to upgrade if you want the best from your classic.. especially with our cars as the pioneering dunlop brakes are long obsolete.. a modern 4 piston caliper set up is really the way to go if one desires to drive the car frequently.. for same price as rebuilding the old....minimally double the pad life...and easier future maintenance to boot..

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