Brakes Binding

[S1.5F]

Hi All

Had a bit of an issue the last few days with my brakes binding. At first everything is ok then as my journey and speed increases the brakes gradually bind up until I have to stop with a huge amount of heat coming from all the brakes. After 10 minutes or so in a layby the car suddenly frees itself and is OK to continue to work. When cold I've checked that the pistons are free and can be pushed back easily...

Anyone had this problem as I could go out and replace the servo/master cylinder etc but it'd be nice to know exactly were to start.

Cheers

Simon

[mep12345]

Haven't had this on the TVR, but had similar on my Rover on one wheel and it was the caliper binding, but not all the time so when you stripped it down it seemed fine and free to move (even a trained motor mechanic thought it was ok) until I got it on a brake test set (the type they use for the MOT) and then they could idenitify the intermittent binding, which was only slight but as it catches it gets hotter catches some more and so on.

Of course if you've got the problem at all wheels then this can't be the issue, but if it is only one - the caliper is where I'd start looking.

[mep12345]

mep12345 said:

Haven't had this on the TVR, but had similar on my Rover on one wheel and it was the caliper binding, but not all the time so when you stripped it down it seemed fine and free to move (even a trained motor mechanic thought it was ok) until I got it on a brake test set (the type they use for the MOT) and then they could idenitify the intermittent binding, which was only slight but as it catches it gets hotter catches some more and so on.

Of course if you've got the problem at all wheels then this can't be the issue, but if it is only one - the caliper is where I'd start looking.

ETA I note you are in Britol, if you have standard 240mm calipers and discs on the front I have a set of good working ones you could swap with yours for diagnosis, but I couldn't get them to you until after 21/6. Let me know if you want to try this

Mark

[Last S4]

I suggest stripping down to the pads, wire brush all debris away and then apply a thin amount of copperslip on the sliders without getting any on the pads. It should all return back after braking without sticking then. When applying Copperslip I wipe on then almost wipe it off.
I had a similar problem on a 205 and it sorted it then.

[GreenV8S]

These symptoms can occur if the master cylinder isn't retracting far enough to open the transfer port to the reservoir. With the transfer port closed the hydraulic system remains sealed off and any thermal expansion causes a pressure buildup which applies the brakes. That leads to more heat and you quickly get into a vicious spiral.

It can be caused because the pushrod adjuster is done up too tight (people like doing this to take out free play at the pedal, but you can have too much of a good thing) or because the m/c is gummed up internally and the piston can't retract far enough.

[Barkychoc]

Also the rubber hoses can collapse and fail to release all the pressure when you take your foot off, acting like a one way valve.

[S1.5F]

I would say I'll have a look at the weekend but rain is forecast here so maybe not. It's definitely all four wheels, so I'll have a look at the caliper pistons and see if I can ease them a little. Peter, from what I've read on the web this was sort of what I was dreading when you say the master cylinder is cruddy would that entail a new seal set etc. or should I just be able to bleed it out?

Simon

Edited by S1.5F on Thursday 4th June 10:17

[S1.5F]

mep12345 said:

ETA I note you are in Britol, if you have standard 240mm calipers and discs on the front I have a set of good working ones you could swap with yours for diagnosis, but I couldn't get them to you until after 21/6. Let me know if you want to try this

Mark

Thanks for the offer Mark, I've actually moved to North Devon now so a bit further down. I'll see if I find the problem and get back to you if i may

Simon

[phillpot]

Can't see it being problem with calipers if definately all for wheels ?
I'd go with cruddy master cylinder and no you won't bleed it out, crud will be "outside" of seal not hydraulic side. Not tried this but if enough movement in pipes may be able to unbolt m/c from servo and pull forward enough to have a look without disterbing hydraulics ?
just bear in mind its the brakes you're messing with, don't tinker unless you're totally confident in your ability ! !

[mep12345]

S1.5F said:

mep12345 said:

ETA I note you are in Britol, if you have standard 240mm calipers and discs on the front I have a set of good working ones you could swap with yours for diagnosis, but I couldn't get them to you until after 21/6. Let me know if you want to try this

Mark

Thanks for the offer Mark, I've actually moved to North Devon now so a bit further down. I'll see if I find the problem and get back to you if i may

Simon

You could be even closer now then as I'm in Plymouth. But offer still stands

[GreenV8S]

S1.5F said:

I would say I'll have a look at the weekend but rain is forecast here so maybe not. It's definitely all four wheels, so I'll have a look at the caliper pistons and see if I can ease them a little. Peter, from what I've read on the web this was sort of what I was dreading when you say the master cylinder is cruddy would that entail a new seal set etc. or should I just be able to bleed it out?

Simon

I assume you can reproduce the problem now. If you want to reproduce the problem at home you can do it by taking one of the callipers off and pushing the piston back. Whichever approach you take, get the system pressurised and then crack one of the unions at the master cylinder. If a lump of fluid comes out and the brakes release you've confirmed the m/c is holding pressure.

Next do it again, but instead of releasing the union slacken the nuts holding the m/c to the servo and let it lift up a quarter inch or so. If this releases the pressure, you know the pushrod is adjusted too tight and the solution is obvious. If it still holds pressure you need to repair or replace the m/c.