break pedal gets hard...

[dave36]

brakes fading away - mistral 2.7td

new front pads and rear shoes, rears fitted too snug and got an overheat - brakes faded away completely, slackened off the handbrake and solved that.
Now brakes poor in traffic (repeated braking), occasional warning buzzer.
Parked up for about 30 mins with no handbrake, the buzzer sounds as soon as I turn the ignition on - how long should it take for the vacuum to leak off?
servo test is ok!
15 year old car, should I be looking at a brake fluid change?

 

[briggie]

master cylinder ?

 

[dave36]

master cyl

thanks briggie, but doubt that one, fluid not dropping at all - thinking that the overheat could mean fluid contamination or that I should be checking vacuum pipes - car was stored for about 10 years in Japan before I got it!

 

[briggie]

bleed nipples not tight enough allowing air in / ? ....... fluid res leaking /not sealed correctly ?

 

[gazrick]

Sounds like glazed pads / shoes - take them all out rub them up slightly with a bit of sand paper and put them back. Gentle braking for 50 - 100 miles should allow them to bed in. They go shiny (glazed) if overheating occurs soon after a fresh install - makes for poor stopping and more overheating.

With regards to the overheat on the brakes, i'd check the seals on slave cylinders and make sure they are not wet, over heats can sometimes kill the seals and you might not notice a drop in fluid straight away. Also drain all the fluid out and replace it with DOT 5.1, which is silicone based and doesn't boil.

Also check the vacuum pipe going to the brake servo, it might work on the stationary test, but it could still have a leak. My Turbo Esprit worked during the MOT, but soon found out it had a very minor leak on the servo connector when knocking it down from 3 figures (On a track of course )

Finally check the brake balancer on the rear end and make sure its still connected and operational.

 

[dave36]

all taken on board

thanks, busy weekend ahead!

 

[lacroupade]

Whatever else it might be, its 100% symptomatic of your rear brake shoes having disintegrated on one or both sides. The bits of loose lining then move around inside the drum, sometimes getting trapped and causing excessive braking, other times freeing up and resulting in reduced braking effect.

Mine got so bad before I discovered the cause that the vehicle was actually self-braking at times.....when I took the drums off the entire lining on one side fell out in a heap of bits and dust on the road....

Don't leave it FFS!:thumb2

 

[fridgman]

If I followed this thread correctly so far the servo checks to be fine. To clarify you should run the engine for a few minutes, switch off, pump brake pedal several times to exhaust the vacuum, hold brake pedal down and switch engine back on whilst holding. If pedal gives under your foot then servo fine.

The need for pumping brakes to get effect should be either air in system, which is most likely, or master cylinder on way out.

If you keep your foot on the brake pedal does it creep to the floor?

 

[dave36]

damn brakes

did the servo test again and its ok, pumping tho' does improve the breaking some, but then the vacuum drops and I get the buzzer.
checked hoses again tonight, there is a bundle passing over the rocker cover, with a heat shielding wrap, pulled it back and found deep scoring on 2 of the 6mm lines running to the check valve.
also there is a perished hose on some kind of sensor attached to the vacuum tank offside wing, that hose connects to the pump, the other hose (facing the engine goes down to a bracket by the engine mounting, its connected to ........ nothing!

Have ordered enough 4mm and 6mm pipe to replace all the small hoses this eve.......... watch this space

 

[dave36]

update on them damned brakes!

New silicone hoses not yet to hand, delivered but locked away till the office opens tomorrow.
Not able to drive the Mistral due to very poor brakes I decided to bleed them - and got a huge surprise, the fluid was filthy at the drivers side rear, I could smell it as soon as it started running into the container.
Stopped the bleed right away and pumped the resovoir near to empty filled up with fresh fluid and repeated at all 4 wheels, so all new oil in the system and no air.
Adjusted the handbrake back to where it was when I had loosened it when the brakes were binding and took her for a spin - first press of the brake and I nearly butted the windscreen!
so tomorrow I shall change the vacuum hoses and hopefully enjoy confidence in the brakes once again.
Another discovery is that the Mistral does not have the load sensing valve over the rear axle? that will be why she does not want to stop with gentle braking on wet grass in 2WD, front locks up but the rears just drive her on!