What are these symptoms on braking

[sonnylad]

Pedal has delay in lifting back up after braking so actually keeps braking when you first lift off pedal, but strangly servo appears to lose servo assistance very quickly after turning engine off.

First thought was servo had gone but now not so sure ,,,,,,any thoughts on this or has anyone encounted the same when servo started to go.

[larrylamb11]

Potentially - partially seized pivot pin on the pedal or mechanism. Possibly the master cylinder seals have perished and filled the servo with brake fluid. Have you had to top up brake fluid? Is the level low? Do the brakes bind?

[sonnylad]

Will check level when i get home but guessing there was a decent amout of fluid as brakes stopped car ok, just pedal felt weird and servo seemed to not hold vacumn

[sonnylad]

Fluid level is ok and looks in good condition so no worry about any loss there

[ukkid35]

I think the rule of thumb is

Do the Easy Cheap stuff first (fluid, caliper plates, caliper seals, even flexi hoses)

If you still have a problem after that then, bad luck, time to ante up.

[larrylamb11]

If the level is ok, start by checking the physical mechanism and lubricating the pedal pivot first to ensure that the physical action of pressing the pedal is correctly translated to action at the servo. See if you can pull the brake pedal back up at all - it should return to a hard pedal stop once released after being pressed and if it doesn't return to its stop of it's own accord it will still be acting on the valve block in the servo giving improper operation. You should be able to detect a very small amount of 'free play' in the brake pedal too - essentially a small amount of movement in the pedal between it moving off its stop and starting to act on the servo, noticeable with a slight change in feel or mechanical resistance - check for this.
If all that is ok, I would also suspect (as you did at first) that your servo has failed / failing or the brake master cylinder has failed / failing and would look and test there first before moving on down the line. The servo should maintain sufficient vacuum after the engine is switched off to give a handful of servo-assisted stabs on the brake pedal before the pedal goes 'hard' (whereupon no servo-assistance is being added). If you don't get any or very little servo-assistance after the engine is switched off then there is a problem with the servo. Potentially a partially blocked vacuum port in the valve block or a blockage in the filter to atmospheric pressure... A blockage or partial blockage of the brake fluid return port from the master cylinder to the reservoir could also cause a delayed reaction in the brakes releasing.
Given your initial description though, my money is on a sticky pedal mechanism / particularly at the pedal pivot.