RR classic 3.9 brakes seizing on

jeff · Feb 8, 2011

Hi all ,
i have a problem with my brakes seizing on my 1991 3.9 RR classic , from cold all the brakes are free , but when it gets hot after a few miles of driving they all lock on, and the pedal goes hard ,
and to release them i have to crack a brake hose nut open , then it will go for a bit until it seizes on again ,

this problem has only occurred since i have changed all the brake pipes/hoses , all i can think that i could of got wrong, is on the front calipers there are 2 hoses to each calipers , if these were fitted the wrong way round could this be the problem? ,

also if there is still air in the system ?

any help much appreciated , cheers

Chrisfrain2007 · Feb 8, 2011

does it have ABS?

jeff · Feb 8, 2011

Chrisfrain2007 said:
does it have ABS?

no ABS , cheers

Khryztal · Feb 9, 2011

Sounds like the master cylinder/booster block is not letting fluid return. Thus keeping system pressurized. Next time it happens crack the pipe union at master cylinder/booster and see if that releases pressure. If so it is that. if not soething further down the system.

jeff · Feb 9, 2011

Khryztal said:
Sounds like the master cylinder/booster block is not letting fluid return. Thus keeping system pressurized. Next time it happens crack the pipe union at master cylinder/booster and see if that releases pressure. If so it is that. if not soething further down the system.

yeah ive been just cracking the nut on the master cylinder and releasing the pressure ,

what is the booster block ?

thanks mate

Khryztal · Feb 9, 2011

Booster block is the abs version of master cylinder. When release the brake pedal does it return all the way? Check the pin that goes into master cylinder does that return all the way out?

jeff · Feb 9, 2011

yep pedal is returning all the way and is free,
its just after a few miles of driving they will all lock on until i release the pressure , and pedal is solid ,
it was fine until i change all the brake pipes , just wondering whether i have got the pipes mixed up on the front calipers? would this effect it?
thanks Jeff

fett · Feb 9, 2011

does it have the brake safety switch fitted if its non abs?, its a 5 pipe block with a plug and wire coming from it, mine siezed on the 72 and blocked the flow to and from the back. I also found the rear flexihose had collapsed and wasnt allowing fluid to retun which kept the brakes on.

jeff · Feb 9, 2011

fett said:
does it have the brake safety switch fitted if its non abs?, its a 5 pipe block with a plug and wire coming from it, mine siezed on the 72 and blocked the flow to and from the back. I also found the rear flexihose had collapsed and wasnt allowing fluid to retun which kept the brakes on.

no don't think mine has that , all mine has is this , thanks

jeff · Feb 18, 2011

I have replaced master cylinder now and it has cured the brakes locking on , but now the brakes fell week, can't lock wheels up , i have bled them with a easy bleeder , so no air , servo seems to be working - if i pull the vacuum hose of servo i hardy have any brakes unless push pedal very hard? does that sound right , or should i replace the servo as well?

only other thing i can think is drove a few miles with the brakes locked on , could this of overheated the brake pads ,

any help much appreciated , cheers

RR classic 3.9 brakes seizing on

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