rear right wheel locks up - any ideas?

[max midas]

Hi, I'm nearing returning my Midas to the road after many years absence and a complete engine/suspension/brakes strip down and rebuild.
Having bled the brakes (once or twice, so only half way there then!) when I've tested them the rear right wheel locks up long before the rest of the wheels start to brake the car.
There is brake fluid coming out of the other rear cylinder when I bleed it, so that part of the circuit is working.
Could it be a defective rear brake damper or could there be a slight blockage in the left rear brake pipe?
Any ideas gratefully received.

[manifold]

Have you adjusted the rear wheel cylinders up equally?

Is this a Mk1/2 or a Mk3/4.

Different bleeding methods for different systems could be an issue also a failed second circuit in master cylinder could be a problem.....ie bleeding back past seal if worn/torn, causing rear to lock up before front.

[rocketron]

Take it to a MOT type brake tester, play one wheel against the other, compare pedal loads, look at the clocks and see if one goes up and down. (Diagnosis not guesswork!)
Best regards, Ron

[max midas]

Thanks guys,

I've adjusted the rear cylinders so far that right rear wheel is spinning freely and the other is catching on the shoes - still the right rear locks up under braking.

It's a Mk 3 conv.

Followed the correct Haynes manual diagram for the car, brand new (correct) master cylinder.

Can't get car to MOT to test brakes as have no MOT - catch 22.

Suppose I'll have to have a very close look at all the slave cylinders to see if there's any sticking.

Mind you, if all the wheels locked up like this one, my Midas would outbrake anything!

[Hans Efde]

It's a simple system, so can't be a big problem to get it right.

First start with the mechanicals:
- brake shoes correct type, good condition and fitted correctly, possibly a small bit of grease on the backplate so they can slide outwards and inwards.
- return springs in good shape and fitted correctly
- adjuster (the one with the square peg sticking out the back) working freely ( I removed mine, took them completely apart and put them together again with loads of copper grease)
- brake pads and wheel drums 100% free from grease and other slippery stuff.

Then the hydraulics:
- both rear brake cylinders in good shape (best to replace left and right at the same time)
- no airbubbles and a good flow of clean oil when bleeding.
- no leakage.
- front brakes properly bled according to the Haynes

Then adjust the mechanicals:
- install wheels and make sure both rear wheels rotate freely
- turn adjuster peg until you feel brakes start binding
- rotate slowly back until you feel wheels rotate freely again.
- let someone push the brakes and make sure the wheels are locked.
- if they lock, release and check they rotate freely again. Sometimes esspecially with new brake pads the wheel may rotate freely but you feel a small ticking. I consider that newness. Usually it goes away, it's just that the shoes have to wear in.

If the wheels won't lock, there is a problem with one of the above. Maybe also check if the front wheels properly lock up when the brake pedal is pushed. Possibly air somewhere trapped. I have flushed liters of brake oil to get all air out (but just poored it in again, nothing wrong with new brake oil).

Before going to the MOT there is nothing wrong with a few brake tests on empty parking lots or empty streets to see how the car behaves and to bed the brakes in. As long as you have the insurance running. During a MOT I also got difference left and right. Oh he said just drive the car around the block a few times and brake thoroughly.I did and when I came back the brakes were fine.

[manifold]

As far as I know, and unless the rules have changed, you are allowed to drive a car without an MOT or Tax Disk to an MOT station for testing as long as you go directly to the MOT testing Station and back again and as long as you have a pre-booked appointment.

Thats what I did when I originally built my convertible back in the 90's....except I had no number plates either....and it was completely legal.

It was very strange feeling driving without plates.

Might be worth reading up though to re-confirm.

Kind regards,

David

[Geoff Butcher]

I remember years ago with my TR3 having a rear brake which kept locking as I came to a stop. Turned out to be a trace of fluid contamination on the shoes which made them grab.

[max midas]

Thanks for all suggestions, of which I think Geoff wins the prize - black sticky stuff on the right rear brake shoes.
Counter-intuitive as I thought the rest of the system was wrong as it didn't work as well as the 'malfunctioning' part.
Now cleaned and after three more bleeds, the car stops just fine.
MOT probably tomorrow.