Intermittent complete brake failure
Turbo Mini Forums

Twice today my car suffered from complete brake failure, nothing on the pedal at all, no resistance, pedal hitting the floor.

First time the car was left for a while and then it was ok, second time I was pumping the pedal, checking everything, gave up and sarted to drive home on the handbrake. 1/2 mile down the road the brakes came back.

I have no idea whats causing the problem but its not even like the brakes work a little bit, there is nothing there on the pedal what so ever, and then mysteriously its fine again

I've checked for leaks and cant find any, and the fluid level hasnt dropped either.

The system has been bled a few times over the last year, and the fluid is a little dirty which I was told isnt ideal. (it obviously went in new and clean)

My setup:
Servo
Twin line brake limiter valve thing on the bulkhead
Minisport 4-pots up front
Minifin drums at the back

Edited by Simon on 16th May, 2012.

http://turbominis.co.uk/forums/index.php?p=vt&tid=170151

check the front hub bearing's and nuts, if they are fucked the discs ccan kock the pads back,

Clevis pin come out?

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1/4mile in 13.2sec @ 111 terminal on 15psi

Hub nut loose, I had this one once....

Clevis pin is good but its a good call as thats what it feels like just a floppy pedal, but alas that is there and working fine.

How can a loose hub nut affect the brakes while stationary?

Edited by Simon on 16th May, 2012.

http://turbominis.co.uk/forums/index.php?p=vt&tid=170151

ah they wont affect anything stationary,

i'm wondering if the master cylinder seals have gone and need replacing, but I dont understand how they could work intermittently, i thought it would just stop working and that would be that if it was the seals.

http://turbominis.co.uk/forums/index.php?p=vt&tid=170151

Ive had clutch masters where the seals seem to try to flip themselves inside out, could be somthing similar happeniung here,

They don't always fail completely, so it is possible that it's the seals.

try pressing the pedal then back of the pressure very slightly and press again gently , usually shows up if its master seals , might have to try it a few times but usually works

http://www.fishfight.net/

i've ordered a rebuild kit for the master cylinder.

does anyone know of any instructions / guides or is it all pretty self explanatory once you start taking it apart.

http://turbominis.co.uk/forums/index.php?p=vt&tid=170151

Master cylinder seals. I think spares do a seal kit

They are fairly straight forward to reseal. Like everything, make sure its clean and use a bit of brake fluid to lubricate the seals as they go in.

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1/4mile in 13.2sec @ 111 terminal on 15psi

Least its not the servo seals, theyre a complete dogs dinner to take apart and put back together!

i had this before. It was the master cylinder in my case although i have seen humped bearings allow the pads to get pushed back as the others have mentioned

bet its the master cylinder mate i had the exact same prob on my old mini

give em hell

Just discovered this thread whilst searching for a solution to my own intermittent brake problem. I am 99% sure its the front wheel bearing / loose hub nut, which i would never have worked out in a million years! TM hopefully saves the day again!!

yeah i used to have it all the time, it turns out to be a worn spacer and nut.

i would recommend changing both if you can

Well its safe to say ive had loose hub nuts for a good 3-4 years, not ideal in a race car! Took the wheels off tonight and the nuts were finger tight..... Torqued them up and the brake pedal feels instantly more assured. The sloppy spongey pedal has gone and the feedback is the same on every dab of the pedal, feels very strange!

Also took the car for a quick test drive and the way it now changes direction feels proper gokart. Cant quite believe its been like this for so long, i just thought all minis were like that!!

Not sure if it will make a huge difference to my times, but with the car being more sure footed and having full confidence in the brakes and their predictability, then heres hoping for a few tenths at least!

If they were worn they were never tight enough in the first place, and even if it is worn, tightening the hub nut would fix that probably instantly without having to replace anything.

nky,

Keep an eye on the nuts,

If they have been lose they can wear the CV and drive flange so they keep coming loose. also any metal that has worn off goes into the bearing,

basicalliy if it come loose abain its new bearing CV and drive flange time.