Brakes sticking on, servo problem?

[Casiofi]

My morris came with a servo fitted to it, which has never caused any problems until now. Car has been off the road for 18 months and is just back on the road now. The problem is that after 10-15 minutes of running, even just sitting idling, the brakes will gradually start binding to the point where the car cannot be moved. I'm assuming that because this happens even when the brake pedal hasn't been touched, means that there must be a fault with the servo (which is a Lockheed, or Lockheed type). So I'm wondering, is there any chance that there's a breather or something blocked? What could be causing the issue? Would I be okay to block the takeoff from the manifold and run the car with the servo still in the circuit but not doing anything? Please forgive me if any of these are dumb questions, I'm pretty clueless when it comes to how servos etc work.

Also worth noting that it had new wheel cylinders all round in late 2014, so I don't think that's a cause of any problems. The brake fluid has also been completely renewed in the last month, fully bled and master cylinder full to about 10mm below the filler cap.

[bmcecosse]

Just pull the vacuum pipe off the servo - and block the hole to the inlet manifold of course..... Now does it still happen ?? Also check that there is a little bit of 'free play' at the brake pedal.

[Casiofi]

With the servo detached it still happens. There is no free play in the pedal though - so it's the pushrod into the master cylinder that should be adjusted?

[Casiofi]

Adjusted the master cylinder pushrod and it's worked a treat, thanks!

[bmcecosse]

Well done.

[Nickol]

This thread is déja vu for me -

SmeProblem, also with a servo except that I Need to remove the push rod and shorten it up because the there is not enough adjustment. Hopefully do this at the Weekend.

Do you Casiofi also have a brake fluid Reservoir located in the engine compartment?