Amazon: Evil Brakes

[devilishdesigner]

pulled out from the shops today and it felt like a rear brake was stickign slightly, kept going and it got worse and started pulling to one side like a flat tire, by teh time I could safely pull over the engine was struggling to beat the braking force. no flat tyres to be found, but my passenger side front brakes were locked solid, couldnt budge them. gave them a good whacking and levering, couldnt do a thing. they released after they had cooled for about 40min, but instead of risking it I got it towed to my mechanic, I have rebuilt brakes before, but dont want to do it on my daily driver, especially as I dont own a torque-wrench. has anyone had a disk brake seize on them before? any ideas what could cause it out of the blue? I drive the car all the time and besides slight variations in initial pedal pressure I have never had a problem with the brakes, they pull up perfectly straight and very effectively.

[222s]

It sounds like the flexible brake hose has collapsed internally, effectively acting as though it is a non-return valve.

[devilishdesigner]

Sounds good, I hope your right, atleast that's cheap enough and the flexi-hoses do look a little old.

[Gordon Hunter]

Hi DD,

Do you have a Girling Mk 2a servo fitted?
Reason I ask is I had a very similair thing happen on my 1800.
Basically the servo jammed on and the more I used the pedal the more locked on the calipers became.
I managed to park up and by thumping the servo with my fist it eventually released the callipers.
I was going to replace the Girling servo with a Lockhead one, but the car has done several hundred miles since without any bother.
I think Mike Gilbert had a similair experience too.
I have heard nothing else but positive reports about the Lockhead unit as a replacement and am still planning to do this upgrade.

Hope this helps,

Gordon

[48pop]

I've had a similar experience with a servo, (not on a Volvo...), my fault, used the wrong vacuum pipe which collapsed and held on the brake. Solution was to turn off engine and wait.....Never had a recurrance with the correct pipe.

Don't think its the servo in this case....Surely it would be holding on all of the brakes rather than just NSF one......I'd go with the collapsed flexi or stuck caliper.

I've got a pair of flexis and overhauled calipers sitting here waiting to go on....Think I paid under £30 for flexis with new bleed nipples..

Cheers
Gerry

[AidanC]

Funnilly enough, this happened recently to my Amazon - same symptons, same side. Problem is that I replaced the master cylinder, pipes and hoses a year or so ago so its most likely to be a sticking caliper piston in my case as I ran out of time and left them as they were. I have the parts to overhaul them but not the time. I'm not looking forward to the rebuild....

Mine doesn't have a servo.

[BillKat]

Sounds like a sticking piston but it's curious that it released itself after a few mins... unless the generated heat got to the fluid, which contracted when cooled and relieved pressure?

[devilishdesigner]

wasn't a few minutes, took around 40 min before it released, it did seem odd though that it was a total release - ie beautifully free-spinning hub once released

[devilishdesigner]

[QUOTE=AidanC;366262] I have the parts to overhaul them but not the time. I'm not looking forward to the rebuild....
[QUOTE]

caliper rebuild is nothing to eb worried about, I did it on my old Kombi, rebuilt the calipers, master... really quite a simple job, would have done it on this but I din;t have a torque wrench and wouldnt want to guess tightness on a brake on my daily driver

[Derek UK]

Originally Posted by devilishdesigner

wasn't a few minutes, took around 40 min before it released, it did seem odd though that it was a total release - ie beautifully free-spinning hub once released

The hose can break down internally with a flap of rubber blocking the return flow. As the pressure gradually reduces the flap returns to the side and all will then seem normal. It might not jam the hose shut for a while but could catch you out any time. If it happens again you can probably release the pressure and confirm the problem by undoing the bleed nipple a fraction of a turn.