Guys, Slidey's brake pedal has gone really hard, as in as soon as you place pressure on the pedal it feels stuck so to speak. Also the brakes are dragging really bad, when u take your foot off the accelerator you can feel the brakes are partially on pulling the car to a stop.

What do you think is the problem....... would the rear brakes be the culprit? If so they obviously need to be adjusted Any thoughts???????

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stevo does slidey have a brake booster?


is there such a valve that lets fluid run away from the brakes? perhaps thats the problem if this valve ever existed

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Sounds like you could have a rubber hose collapsing. Like the clutch does, they get old and swell shut. Fluid goes to the brakes under pressure, but won't come back.
I'd change all the hoses on whichever end is dragging.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Sweet Doc, will check that tomorrow......... i think that it will be the rears due to the fact that the fronts are brand new, whereas the rears are just reconditioned....

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could also be crap in the master cylinder blocking the bleed-back hole - depends if all wheels are locking, if it's a pair, or if it's a single.... figure that part out and it's deduction to see which part is dodgy...

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Will check that also, thanks for the response skssgn

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I got nuthin......................

OK........checked the rears this afternoon, they were fine. Checked both fronts and they were bound up quite badly and the brake pedal was still hard at the top of the pedal.
From this i assume that as skssgn mentioned the lines or Master Cylinder bleed back hole must have grit or something caught in the line, thus causing a build-up of pressure forcing the pedal to go hard?????

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I got nuthin......................

If both fronts are tight yes it's gotta be the MC..
BTW if there's a restrictor valve in top of MC, chuck it away. You don't need or want them with front discs. They were designed for use with drums.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Ok, Doc......... once again will check that tomorrow

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I got nuthin......................

I'd suspect this restrictor valve may be blocked. Seen that happen before. Another reason to lose it.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

hey Doc, what's the restrictor valve look like? - I don't know that I've ever seen one

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did I tell you that I won a trophy?

It's a little round thing with a flap in the middle. Basically a 1 way check valve that leaks back.
To see if you have one, remove the pipe and connector from top of MC. Poke a bit of wire or a nail in there gently. If it hits something, there's a valve in there. (It's above the spring).
These things were designed to keep a little pressure in the drum brake system, for quicker response when you hit it. But, they can make discs drag- the caliper seals are trying to flex the piston back on release, but this pressure stops it. Bad news...

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Just checked the manual for a single circuit master cylinder, it shows the valve as being in two parts. If you remove these for disc brakes the master cyclinder then has exactly the same parts as the clutch cyclinder. Does this mean you can use a spare clutch cyclinder as a brake master cyclinder if you have disc brakes?

It depends, but it's not a good idea.
If tin tank MCs, no, the flanges at bottom are in different positions.

Apart from 850 single leading shoe brakes (0.75" MC) the bores are different too. Brake MCs generally are 0.70", except 998 Cooper, 0.625"- but the clutch MC is supposed to be 0.75".

A 0.70" MC will just work for the clutch, but it will tend to drag- not enough oil displacement = clutch travel.

OTOH, if you use a 0.75" clutch MC for brakes, the pedal pressure needed will increase.

So no, as I said, not really a good idea.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Ok, bled the brakes this evening and went for a drive................ problem still exists. Checked the lines off the calipers for decay - they are all good. There is no restrictor valve in the Master Cylinder, no issues there. And also no grit in the lines or MC - all clean.

When u initially brake, the pedal feels good, but brake again and the pedal goes hard and you can feel the calipers partially clamped, but then it releases slowly and is all good. The seal kit in the calipers are new but may have perished as the brake assembly was built many years ago - could this be the issue??? (perished seals not enabling the calipers to release properly?)

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I got nuthin......................