Not sure if anyone has any previous experience or can advise.
I have undertaken a significant refurbishment of my 1972built /1973 registered TR6 including wheel cylinders, discs flexible hoses and master cylinder. Initially the brakes were fine (pedal is very solid with very little free movement), however a sticking brake problem has crept in over the last few days only becoming a problem after a few miles 10 to 15 and modest use of the braking system, when the car is left for 30 minutes the brakes free off again.Last week one of the rear brakes stuck evidenced by heat and hot friction material smell, this week both of the front brakes stuck sufficiently to blue the discs after completing approx 10 miles without problem then a further 2-3 miles after they started sticking.
Whilst the original front callipers have been retained the flexible pipes have been upgraded BF Goodridge S/S braided , rear wheel cylinders replaced and the master cylinder replaced. Whilst fitting the new TRW master cylinder I bled the rear brakes first which was straight forward however the front brakes would not bleed until I removed the outlet union and cleared the drilling hole from the cylinder (by hand with a small phillips screw driver) after which the pedal pressure was very solid. After the initial rear brake sticking problem I removed the master cylinder cap to check the vent hole was clear, this appeared fine but was surprised to see a small amount of black sediment in the bottom of the cylinder, the cylinder was new and bled with clean new DOT4 fluid.
I suspect there may be a blockage due to either a fault with the front master cylinder section (cleared to enable bleeding) or sediment left after manufacturing causing a partial blockage which can be overcome by the braking pedal effort applied but not overcome by the much smaller return rear brake springs/caliper relaxation forces, or only allowed to dissipate extremely slowly.
I would be grateful if anyone has any similar experience or knowledge, Alternatively is it possible that the servo could be faulty as this is still the original unit