Seizing brakes

[HQentity]

Hi guys,

Not a good day today. After having sailed through the MOT my dolly has had a few issues today. Driving through town the brake pedal became very stiff. By the time I had travelled a few miles, the pedal would only move a few millimetres. It was still operating well though. By this point the brakes were also seizing quite badly though.

When I got back I jacked the car up and went straight through one of the jack points (great MOT!) but found all the wheels were stuck fast.

Am I right to think something has gone wrong in either the servo or master cylinder? How do I check what to do? I had a look at the master cylinder and the little air vent in the top wasn't blocked. Everything looked alright to me.

Also while we're on the topic, on Rimmerbros, where it says about surcharges, what do you pay?
For Instance, here it says £125, surcharge £60. Does that mean if you send the old part back, they charge £65? Or they charge £185 and refund £60 down to £125?

[sprint95m]

It does sound like a brake master cylinder problem but you have single line brakes?

Try slackening the brake pipe union that goes directly into the BMC......if the brake free up then the problem lies with the BMC.
Then we can investigate further.



By the way, you pay the surcharge then receive a refund of that amount once you have returned your old unit.
Which in this case means they charge £185 and refund £60 down to £125?




Ian.

[Richard the old one]

I think you will find that most people do not use the jacking points but either jack up on the front sub frame or the centre of the rear axle and then put a pair of axle stands either under the subframe or back axle for safety while working on the car.

[Mahesh]

Either of those sound most likely, and removal inevitable in that case.

Might be worth cleaning up and putting in a seal refurbishment/replacement kit for the money they are.

My Sprint ones are unlikely to fit, or I'd post them out.

[Jon Tilson]

Are all the brakes staying on or is it just the rears?

The rears often stick on as the rear flexi hose collapses and acts as a one way valve, keeping the rear brakes
on.

This would make the pedal feel a bit stiffer.

If its all 4 wheels I suspect the servo or master cylinder. If the spring breaks in the master cylinder it could cause this.
The test would be to undo one front bleed nipple. This should release pressure and all 4 wheels should then go free again. Reconning a master is not too bad but sadly the spring no longer comes in the kit. I'm sure someone could find you a spare.

PM me if you cant find one.

Jonners

[HQentity]

It does sound like a brake master cylinder problem but you have single line brakes?

Try slackening the brake pipe union that goes directly into the BMC......if the brake free up then the problem lies with the BMC.
Then we can investigate further.



By the way, you pay the surcharge then receive a refund of that amount once you have returned your old unit.
Which in this case means they charge £185 and refund £60 down to £125?




Ian.

I slackened the bolt off and a small amount of brake fluid came out, which immediately released the brakes. I tried it twice and it was exactly the same both times. I took the pipe out completely too and no further liquid came out which I'm assuming is right?

Ok thanks for the help

---

Jonners, all the brakes are sticking hard, I think I'll try refurbishing the brake master cylinder? Hopefully thats all it will take! I'm thinking maybe the MOT centre was a bit more heavy on the brakes than I have been and have popped a seal or something!

[sprint95m]

That means the fault lies with the brake master or servo or even perhaps the brake pedal.

I would start by investigating the BMC.
When you remove it, take a look at where the piston is. It should be back against the circlip.......





Ian.

[HQentity]

Hello everyone,

Just thought I would post a quick update!

On the way home from work I had to brake quite sharply at some traffic lights, and to be honest, since then the problem with the brakes seizing went completely. They were working wonderfully the whole way back and the pedal was traveling as normal. When I got home I pumped the brakes and still no trouble or stiffness, although the revs did go up a bit each time, so I was considering checking the servo?

I have a master brake cylinder repair kit now anyway so I'm doing that when I have the time, and then maybe having a look into the servo too? The vacuum pipe fasteners look a little rusty so I wondered if that had something to do with the revs, but I don't ever remember them rising like that in the past.

Anyway, overall I was thinking that there was something a little bit stuck somewhere, and a good punch of the brakes has unstuck it! fingers crossed anyway!

[HQentity]

For those of you that are interested, the brakes are fixed!

It all began Sunday afternoon, my first day off after a troublesome week of travelling around sussex with as little use of my brakes as possible. I can tell you, I've learnt more about whats possible with a car gearbox then I ever thought I would this past week! Thank god I have my brakes back again!

As I was saying, Sunday afternoon, I went out, spanner in hand to attack the Master cylinder. I'd already found which ones I needed and had them all set up ready to go. Removed the brake pipe which came away with ease, little bit of fluid came out as if to taunt me, as per normal. Undid the bolts holding on the earth cable and support, the rusty support came away, no worries at all. On to a winner!
I don't know how long that cylinder has been there, but I dare say it was joined to the servo sometime in the 17th century. My god I think I lifted the front of the car off the ground trying to remove it. At least I've found a good jack point! Anyway it wasn't moving so I reassembled the whole thing and had a good long think about my life decisions buying a classic.

Monday morning I went out fresh faced and ready to go again, WD40 in hand and a boiling cup of water in the other. I loosened everything up and wiggled it about a bit and scraped the worst of the scum off the cylinder. After pouring more WD40 than I care to admit uselessly over the body of the cylinder and boiling hot water over it too, I began shoving everything in my toolbox between the cylinder and the servo and hammering it in.
Several screwdrivers, chisels and files later, there was an almighty crack and the cylinder simply pulled away. For those of you that have seen the film '127 hours', that roughly resembles my feelings when I finally removed the cylinder from the servo.



The evidence was obvious. The amount of rubbish sitting in and around the piston was monstrous. Here is the Master cylinder face, with what I can only imagine is 40 years worth of road grit:




Luckily enough for me, none of it had damaged the cylinder. Everything was beautifully smooth inside, and some methylated spirits later brought everything up great:





I refitted the cylinder (after cleaning up the servo area in general) and bled the brakes, which I must say in itself was quite a challenge! Lots of white fluid came out which led me to believe I could do with changing the whole brake fluid system, but that is for another day. My brakes are now fantastically high on the pedal and responsive. One question I do have, on the drivers side, where exactly is the bleed nipple for the rear?!

[geeksteve]

on the drivers side, where exactly is the bleed nipple for the rear?!

Only one bleed nipple on the back. Special..

Steve

[HQentity]

That would explain the difficulty in finding a second one then!

[HQentity]

Hello all,

having changed the brake master cylinder seals back in 2015 (as per this post), I'm experiencing the same symptoms again, with the front brakes binding, and fluid coming out when I undo the brake pipe union.

I'm thinking about investigating the servo, any advice? Or just do the same as before and replace the seals?!

Thanks!

[tony g]

Does fluid come out of the caliper bleed nipples then release the brakes? If so it may be front flexy pipe(s) collapsing or master cylinder again

Tony

[HQentity]

A couple of ml came out without much force, and no noticeable change to the pressure on the pedal. The hard pedal builds up well before the brakes start to seize, then when it only moves around 1cm the brakes lock up on the front.

[Carledo]

I've had this problem with various cars over the years, the brakes gradually applying themselves till the car becomes undriveably locked stationary with the pedal rock hard and no free travel. The last time was last week on a customers Sprint! But it is particularly prevalent amongst the Peugeot/Citroen/Fiat family of vehicles. This is nearly ALWAYS down to the servo!

A different test for you, when the car is locked stationary, DO NOT release hydraulic pressure at the pipe, instead remove the stiffener bolt on the turret and loosen the master cylinder to servo nuts to the end of the threads, pull the master cylinder forward as far as possible, then see if the car will roll from pushing it! This will determine if the problem lies with the servo (car CAN be pushed with master cylinder bolts loosened) or hydraulic system (car CANNOT be pushed with m/cyl bolts loosened)

Now I don't know, nor do I know anyone who DOES, what causes a servo to misbehave in this way. Since a second hand servo is almost always cheaper than even a rebuild kit (if you can even get one) I simply replace the servo, job done! And i'm not sufficiently curious to dismantle the old one to see if I can see what's amiss, it just goes in the scrap pile with the rest of the rubbish!

Steve