aaargh - I've had a seizure!

[bstark]

I've got to the bottom of the brake problem I've been having - one of the pistons on the driver's side caliper has seized.

 

Unfortunately, it has seized in the completely 'in' position and I am struggling work out what I can do to free it!

 

I have sprayed WD40 all around the inside of the outer seal, but I can't get a grip on the piston to either twist or pull it.

 

Is it practical to G-clamp the other, free, piston and then pump the pedal to try and force the seized one free?

 

If not, has anyone got any other suggestions? I don't really want to have to replace the whole caliper unless I have to, but I do want to get it fixed before Saturday (Brooklands am session!). Help!

 

Bob Stark

Supersprint first-timer

[ashaughnessy]

Why bother with a G-clamp? Put everything back on the car, bleed the brakes, put a pad in the side that is free but leave the pad out on the side that is seized. Then press the brake. If the seized piston comes free, it will either pop right out (with impressive force, perhaps) or will come out enough to give you a good purchase on it. Leave the outer rubber seal off the seized side so that it doesn't get in the way of the piston coming out. If this won't budge it, I would have thought the caliper was scrap.

When refurbishing, you should do both side of the car to make sure you have equal braking effect.

Anthony

[Fred]

dont want to sound harsh and not ment to offend

you obviously dont know what your doing what anthony said is true scrap the caliper

or both you can fit seals etc and never know when it will leak or fail the fact it's seized the piston or barrel must be corroded inside i dont think id want to be in front of you at a pit stop.trade in the old ones for replacementsquestion.gif

 

fredid=blue> biggrin.gif

[R2D2]

If you have standard Spitfire Type 14 Girling calipers I would replace them with re-conditioned ones. I had a "lazy" caliper last year and I replaced seals cleaned the piston, cleaned the bore and it just kept on being a problem.

 

Ther have been quite a few sets of calipers on the For Sale Board for a reasonable price.

 

I think Rimmers have exchange re-conditioned units in stock at about £80 each including the VAT.

 

The James Whiting Alcon 4-Pots are pretty good and a bolt on replacement but quite a bit more expensive.

 

[bstark]

Fred - don't want to sound harsh? "you obviously don't know what you're doing" sounds a bit blunt to me! Only kidding, you're probably right but if the piston is simply stuck to the back of the caliper, rather than being horribly corroded then it is worth a try (the face of both pistons, and what I could see of the piston barrels in front of the seals, look fine on both sides).

 

I've managed to source a replacement caliper locally for about £60. If I have to replace the caliper, is it safe to simply clamp a steel braided (I assume aeroquip) brake hose with a pipe clamp prior to removal? Or do these hoses need a special tool / technique?

 

Bob Stark

Supersprint first-timer

[ashaughnessy]

Good question about the steel braiding. Last time I had my brakes apart was the first time I'd done it with steel braided hoses. It didn't seem right to clamp them with a normal hose clamp, and when the clamp came off the hose didn't spring back to shape like a normal rubber one.

 

As for scrapping the calipers, I refurbished mine when one piston became "lazy". The piston and cylinder cleaned up a treat. The siezure was due to surface dirt and very light corrosion. Using very fine wet and dry paper brought the shiny surface of the piston up nice and shiny with very little obvious sign that I had been at it. The pistons looked almost as good as new. You'd need to make a judgement about the condition of them before deciding whether to refurbish or replace.

 

Anthony

[sjwb]

Clamp a braided hose! Are you NUTSquestion.gif Inside that braid is a nice stiff walled PTFE(?) tube which will not recover from deformation beyond its natural plasticity. Clamp it - scrap it. A better solution is to seal the reservoir cap - if air cannot enter, fluid cannot escape.

Further NEVER NEVER use carborundrum on brake parts:

a) you will never remove the residue and

b) the piston seal dia is finished to a finer degree than you can achieve with W&D. There is then of course the question of paralleism, roundness - need I go onquestion.gif

 

Steve B

 

Edited by - sjwb on 30 Apr 2002 22:33:53

[Mark H]

He,s right you know NEVER clamp a braided hose!!!!eek.gif

[ashaughnessy]

I'd like a third opinion about this piston/wet-and-dry issue.

 

When I cleaned up my calipers, I used 1200 grade paper wetted with meths. I used light finger pressure and was quite gentle. The stuff I was taking off was stubborn dirt and very light surface corrosion. When the dirt was off, there was no pitting or other trace of rust. The surface looked beautifully smooth. I could only see the surface scratches put there by the wet/dry paper when I looked at bright light reflections, otherwise they were invisible. The piston isn't a perfect mirror finish to start with (though it is pretty shiny) and I don't believe my surface scratches were any deeper than the existing surface irregularities. As for altering the diameter, roundness, or parallelism of the piston noticeably, I just don't believe it (though I'm willing to be corrected).

 

Using a clamp on braided hoses - bugger. I was worried when I did it. Do you think I should now replace my hoses because of possible damage?

 

Anthony

[R2D2]

 

Anthony,

 

Clearly when calipers and pistons are manufactured they are ground with abrasives but they are then subjected to a well controlled machine cleaning process.

 

Using wet and dry and then cleaning by hand doesn't really guarantee to remove all of the particles that can be left behind.

Aassuming you used a P1200 paper, this has an average particle size of about 15 microns. I think this is too big for a relatively soft rubber seal and could cause uneven wear which will eventually result in a weep/leak.

 

I tried to clean my pistons and calipers with meths and this is why I wasn't successful. It wasn't the dirt that was causing the problem but the slight corrosion in the bore leading to a surface roughness which gripped the seal. (Probably because I didn't change brake fluid often enough)

 

I decided not to use an abrasive but to replace as I beleive this is the safest option on a high performance car.

 

I also don't like clamping brake pipes because it can cause damage that you don't see until it is too late.

 

I am sure that lots of people will disagree due to cost but a "best practice" approach to brakes is conservative. At the worst it will cost a little money and it will never cause an accident.

 

 

 

 

 

[ashaughnessy]

I'd like a fourth opinion...OK, I give up, I know how to take a hint :-) Cleaning with wet and dry is not recommended. However, £80 plus VAT (mentioned earlier by Chris) is quite a lot of money, not a little money. In future if I can't clean the pistons without abrasives, I'll replace.

 

I think I'll replace my braided hoses while I've got the engine out. I won't clamp them again.

Anthony

[sjwb]

Forgive me if I sounded like a zealot, but there are two things I firmly believe, don't f**k with brakes and tires.

 

Steve B

[Blatman]

£80 plus VAT (mentioned earlier by Chris) is quite a lot of money, not a little money.

Perspective. A lot if you haven't got 80 quid lying around. Not much if you total your se7en 'cos of a half arsed repair on a vital component, and you end up getting sued for allsorts 'cos you rear ended someone driving a Roller with a Claims Direct card in his pocket............

[Bricol]

Once had a front brake pipe fracture - bent it over and hammered it flat for 6" - then drove 7 mile to a mates house (along m62) to use flarer to replace pipe - was fine until I braked at end of M62 slip road- had to hold full right lock because of the in-operative right brake! Exciting - overheated the working brake disc too! Dont worry, I've grown up a bit in the past 12 yrs!

 

I think Andrew Page motor factors can get good prices on recon calipers - they use Brake Engineering who won't sell direct (unless you use a lot of calipers!) - good price and quick - got me some for a Lancia Integrale - not the most common vehicle in the world!

 

Just don't do wht i did - hold front brake caliper in righ hand - point compressed air line into hose connection to blow fluid out bleed (to empty caliper to exchange at Andrew Page) - then gimace, make several comments, and frantically search for vice to push piston back that has just shot out and trapped your fingers and now wedged lop-sided! No damage done, another lesson learned!

 

Bri