I finally diagnose the fault with my brakes.
October 10th 2019
It has been a while since I've been able to work on the Morris due to work and other commitments but I'm determined to get to the bottom of this braking problem.
Thanks to a conversation I had on the owner's club forum I have a couple of leads to follow...
Firstly I noticed that the previous owner had only replaced the flexible brake pipe on the left side of the car so just to eliminate one possible problem I decided to replace the other one too. I'm glad I did because the old pipe was pretty cracked and in a generally poor state. Once the new one was fitted I bled the brakes to release the air I'd introduced into the system and then I took the car out for another test drive.
This time I was careful not to drive too far from home as I didn't want a repeat of my long walk if the brakes started to seize up! I'm glad I did because before too long I felt some resistance building up on the front brakes so headed home straight away. Sure enough, they had started to bind once again. Not good!
Ok, onto the next possibility. Someone on the forum suggested that the control linkage of the master cylinder had been incorrectly adjusted. If this was the case then the MC piston wouldn't be able to fully retract even when the brake pedal had been released. This means the recuperation port would be sealed so any excess pressure build up in the brake circuit (due to thermal expansion) couldn't be relieved back through the MC. Sounds plausible so let's take a look...
I started by removing the seats and the front carpet before unscrewing the floor panel that covers the MC and transmission.
The old rubber gearstick gaiter was in a terrible state and virtually crumbled away as I tried to remove it. Fortunately I had recently ordered a new one which will be fitted when I reassemble everything.
Once the floor panel had been removed I got my first good look at the MC and linkage. There seemed to be the correct amount of free play (3/4") as stated in the workshop manual but hang on, why does the pedal now feel so slack? It goes down almost to the floor now whereas before it was quite firm.
After a little investigation I discovered the truth- Whoever fitted this MC did actually adjust it for the correct amount of free movement. However what they didn't realise was that when you screw the floor panel back down, it slightly depresses both the brake and clutch pedals.
This results in exactly the scenario that was suggested on the owner's club forum. The MC piston couldn't fully retract even when the brake pedal was released. The linkage needs to be adjusted so that it's in the right position when the floor panel is in place. As soon as I unscrewed the panel and allowed the pedal to come up fully, all the excess pressure in the brake circuit bled back into the MC reservoir which is why the pedal now feels so slack.
Just for the sake of experiment, I replaced the floor panel but didn't screw it down around the pedals. I also went around the car and adjusted all the brake shoes outwards so that they were just contacting the surface of the drums. In order to achieve this, the adjusters had to be wound almost all the way out which doesn't seem right for new brake shoes but I'll cross that bridge when I come to it. For now let's take the car for a little test drive...
17 miles later and all is well! No more brake binding problems so I returned home happy. I replaced the gearstick gaiter with the new one and gave the car a well deserved wash.
Finally, I decided to book the car into a local classic car specialist here on the Wirral in order to get the whole braking system checked over and adjusted properly. As I'm only an amateur and the brakes are a safety-critical part I wanted the peace of mind to know they had been looked at by a professional. While the car is there they will also be replacing the rear leaf springs which were diagnosed as the cause of the slight lean to the right! The worn tie-bar bushes will be getting replaced as well.
In anticipation of having a fully roadworthy car, I have joined the Wirral Classic Car Club with the intention of joining in with some of their local events.