MG Car Repair: Uneven brake pressure, service invoice, ring seal

Question
QUESTION: Hello Howard,
Are you well? I have a 1977 MG Midget 1500 which is due for a complete service. However, in order to drive her to my garage, i need at least the brakes to work! After hearing what sounded like the pads against the disc on my front right wheel, I've removed the caliper to find that the inside pad was worn down whereas the outside pad was as good as new. I have not looked at the left wheel yet. I heard that this could be a faulty "T" valve. The piston is slightly rusty but moves using hand tools.
At this point, I need to bleed the system, put new pads and get it to the garage for its due service. In the mean time, all tips and advices on what may be wrong with the uneven pressure is certainly appreciated.
All the best,
Pierre

ANSWER: Hi Pierre,
When one of the two brake pads is worn out and the other is like new the piston on the new side is sticking in it's caliper cylinder or there is a restriction in the fluid passage between the two sides of the caliper. The only other cause is that the pads are tight and not free floating.
Sorry, I never heard of a "T" valve. Are you talking about the "T" fitting that the pipes go into that branch to each of the front wheels? If so, that is not a valve. It is just a "T" connection and has no restrictions in it.
Howard

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QUESTION: Hi Howard,
Thanks for your prompt note. I was wondering whether the caliper comes apart easliy. I would not mind taking a look inside the part myself, if I know this is an easy procedure and in order to cut down the service invoice! What are your thoughts on this? Alternatively, I can probably replace the caliper, should it be faulty and beyond repair.
Thanks Howard.
Pierre

Answer
Hi Pierre,
The two halves of the caliper just come apart when you remove the bolts that hold them together and there is nothing complicated about it. In the dealerships we were told to not take them apart probably because they could not supply the small "O" ring seal. However we often did it anyway when forced to because of a shortage of parts at the time. I found that 90 of the time the "O" ring was still OK and didn't need to be replaced.

We used compressed air to get the pistons out and wrapped rags around the caliper so as not to get shot by the piston as it came out.
Howard