Brake Pedal goes soft...

I’ve got a small issue, in the fact my brake pedal appears to go soft at the most inopportune moments…

It appears to be very intermittent, however, always works on the second “pump”.

Also from time to time, when momentarily sat with foot on the brake, foot slowly starts to sink to the floor.

I’ve checked for leaks, and not losing any brake fluid, and the vehicle is braking well.

Replaced brake fluid, and bled the brakes.
Replaced Rear Brake shoes, although noticed rear half of the cylinders are seized, got these on order so replacing soon.

However, I am now thinking it might be down to a servo problem.

But without knowing exactly how the servo works, I am unsure how a failure might manifest itself.

Any ideas, on what problem might be, or some quick and easy things to check??

Help\advice appreciated.

Thanks, Paul W.

PS.
1986 Ex-Mod LandRover 90, with Drums on the back.

Put brakes on and start the engine. Your foot SHOULD sink a bit, if it doesn't, your servo is stuffed.

Have you checked your front wheel bearings? If they are loose, going round corners will push the pistons back into the caliper and cause you to have to pump the brakes once. Oval drums on the back will have the same effect.

Thanks Jim, think you might have hit the nail on the head.

I will test Servo, but pretty sure I noticed it sink when engine is started.

However, I've also picked up a slight steering wheel vibration, so could also point to loose front wheel hub. Was also informed by the previous owner that there was a problem, with the front hub, that was fixed for the MOT.

Good call, will check. Thanks again.

Bearings have gone on the front offside wheel, so hopefully found the fault. Thanks again.