Very Hard Brake Pedal

[Rod1883]

..not on the TR (although that is quite firm and needs a fair weight on the pedal with the old style twin master cylinder) but on the Midget. This is an early car (Oct '61) and has a similar twin master cylinder to the early TR's. It is drums all round and after adjusting the brakes the pedal is really firm (it was quite firm before) and takes quite a press to brake hard. The master cylinder was replaced about 6 years ago and the brakes have always required some pressure but they just seem much firmer now.

The rear wheel cylinders were replaced at a similar time to the master, and the front cylinders and hoses in the last three or four years.

I'm wondering if the Master cylinder has developed an issue.

My first steps when I next get the car (it lives in a lock up ~5 miles from home) is to bleed the brakes as it is due to be done, but I'm wondering if anyone has any other thoughts on what the issue might be.

Thanks

[DaveB66]

Rod

I had what sounds similar to your problem over the weekend, although on myTR4. In the end we traced it to the fact that the rear wheel cylinders had become stuck to the back plates and wouldn't slide as supposed too. I have a twin master cylinder arrangement on the TR4 giving me a split between the front and rear brakes.

Dave

[MKTR]

I have seen this on TR and MG forums before and the general concensus seems to be a stuck master cylinder or collapsed flexible hoses.  Maybe either can be rulled out through bleeding?

Mark

[BlueTR3A-5EKT]

There are two bore sizes of master cylinder fitted on Sprite/Midget.   The bore changes when disc brakes are fitted.   That bore change would affect pedal pressure.

Have you mixed up the fluid type in the master cyl?   Using regular in a system previously filled with silicon causes a heavy pedal and the cylinder seals to swell and stick.

[Rod1883]

Thanks for the comments.

I've managed to spend a little bit of time looking the set up today. I think my issue is that the push rods on the Master Cylinder are not set up correctly with the required small amount of free play, and from a bit of research on Midget and Sprite forums it seems that this may be stopping the pressure in the braking circuit being released when the pedal is released as quickly as it should.

It's been like this for 6 years but perhaps my recent brake adjustment activity has simply exacerbated the situation and made the hard pedal more noticeable. I've tried to slacken things by adjusting the pedal stop but I think I need to shorten the push rod (and the clutch one too) whilst keeping the pedal heights correct via the stops. I wonder why the clutch doesn't have the same pedal issue if that clearance is also required for fluid return.

My next steps are to work out how to get the push rods out so they can be adjusted - probably I need to reduce the length or remove the pedal stops altogether to do this. I will also bleed the brakes and check that the rear cylinders are free to slide as suggested above, and recheck the brake adjustment all round.

Peter - The Master is definitely the 7/8" variant and it has only ever had 'normal' brake fluid although the system did have silicone fluid in it before it was thoroughly flushed and bled when the new master and all wheel cylinders were fitted.

During my research I've established that the clutch and brake bores, although the same size, have different components. The Brake side has a valve assembly in it but I'm not sure why, or what it does. Is it do do with the fluid returning to the master after the pedal is released? If so, why doesn't the clutch bore have one? Can anyone explain as I like to understand if I can.

Any other thoughts are welcome as always.