Luke-Mia Posted November 15, 2021 Report Share Posted November 15, 2021 Hi all. I am checking out my braking system to check it is in good order. I am having to rebuild or replace my brake master cylinder, I have removed it from the car. My question, now it is removed from the car I would like to check the measurement of the brake servo piston travel, unfortunately I have not been able to find out what it should be. Thank you. Luke. Quote Link to post Share on other sites
John L Posted November 15, 2021 Report Share Posted November 15, 2021 If you place a straight edge across the servo 2 mounting bolts, the pin of the servo should be 0.011" to 0.016" ( 11 - 16 thousands inch) below the master cylinder mounting face. I got this from the TR5 supplement workshop manual to the TR4/A Might be quite difficult to change it, if its wrong, as the adjuster is Loctited in manufacture. John Quote Link to post Share on other sites
mhossack Posted November 15, 2021 Report Share Posted November 15, 2021 (edited) Wrong thread Edited November 15, 2021 by mhossack Wrong thread Quote Link to post Share on other sites
Luke-Mia Posted November 15, 2021 Author Report Share Posted November 15, 2021 Hi John Thank you for your reply, I will use that information when refitting my brake master cylinder. I was asking about the brake servo pushrod travel when the brake pedal is depressed, I have not been able so far to find out that measurement. When I refit my brake master cylinder will I have to bench bleed it, I have heard that term but have no idea how to do it or if required, I will be using an Ezibleed if that helps. Luke. Quote Link to post Share on other sites
Mk2 Chopper Posted November 16, 2021 Report Share Posted November 16, 2021 If you end up replacing the MC, you may well have to adjust the servo push rod, as there is sometimes a slight mismatch between original and aftermarket. Bench bleed is simply filling with brake fluid and purging air to the outlets before you attach the MC to the car. As long as there isn't the mismatch as mentioned above, it will bleed fine fitted on the car. Gareth Quote Link to post Share on other sites
Luke-Mia Posted November 16, 2021 Author Report Share Posted November 16, 2021 (edited) Thank you Gareth John pointed out you need 0.011" to 0.016" clearance which I had read on the internet before Johns reply and confirmed John's dimensions. I knew something was wrong with my brake servo and brake master cylinder, because when I removed my brake master cylinder someone had put a washer between the brake servo and brake master cylinder, doing online research was when I read about John's dimensions. I will now be replacing my brake master cylinder and not rebuilding. Can you please explain more fully how to bench bleed the brake master cylinder, unfortunately I did not fully understand. I am still interested to find out the travel of the pushrod. Luke. Edited November 16, 2021 by Luke-Mia Missing words. Quote Link to post Share on other sites
John L Posted November 16, 2021 Report Share Posted November 16, 2021 The travel of the push rod will be the amount the master cylinder pushes the fluid to the callipers and the slave cylinders, if you still have air in the system that's how much the rod will travel, the servo just makes pushing it easier. You shouldn't be able to compress the fluid, it will a tiny bit. If you take off your old master, and block the the 2 lines out the pushrod shouldn't move if the seals are good, if it moves the seals are gone. If the callipers are right up to the discs they will not travel that much, if the rear shoes are not adjusted up correctly the pedal will have travel. One way you can confirm which ones are causing the travel, use brake pipe clamps on both the front flexibles and press the brake, if it now hard and little travel, the problem will be in the front, and not the rear, if you still have a long travel it would indicate that the rear is still got too much travel or there is air in the rear section. If you change the clamps to the rear flexibles, and the pedal is now hard you know the fronts are ok, its the rears with the travel or air. John Quote Link to post Share on other sites
Luke-Mia Posted November 16, 2021 Author Report Share Posted November 16, 2021 Hi John. Thanks, but at the moment my car has no brake master cylinder, so it is only the physical distance the brake servo piston/pushrod moves when the brake pedal is depressed I am after nothing else. Luke. Quote Link to post Share on other sites
Luke-Mia Posted November 16, 2021 Author Report Share Posted November 16, 2021 Hi John Please ignore my question, the penny has just dropped it is a stupid question, no fool like an old fool sorry. Luke. Quote Link to post Share on other sites
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