Testing remote brake servo

[Kevin-G]

Hi, I have been having trouble not being able to get the idling speed down on my rebuilt 1098 engine. So go looking for air leaks.

Anyway, have a remote brake servo that I'm not completely convinced is working the way that it should.

If I disconnect the servo vacuum pipe and plug the hole in the inlet manifold the revs do drop considerably. Ok I think, so the servo reservoir must be leaking. If I then suck on the vacuum pipe, I cannot get a vacuum to hold. I sense a sort of pulsing, but no vacuum. I have a non-return valve fitted and it is in the correct way around.

Connecting the vacuum pipe up again, I find that at idle if I press the brake pedal, the revs rise momentarily, presumably as the mixture weakens, and then fall back again. When I release the pedal the same happens, momentary rise in revs which falls back again.

Can someone please confirm that this is normal behaviour or not. My modern car holds a vacuum in the servo reservoir for days. Should the remote servo, which is less than a year old, hold a vacuum, without a constant suck from the engine, or am I expecting too much.

Many thanks

Kevin

[Kevin-G]

No one know anything?

Who's going to pull off their vacuum pipe and give it a suck for me

[philthehill]

I think that you are expecting to much for the type of servo fitted to Minors as an after market item for it to hold its vacuum for days. In my experience the servo does not hold its vacuum for very long.
Isolate the servo from the manifold/engine by putting a suitable size bolt into the vacuum pipe & tighten the hose clip to hold it in place.
Then get the engine/carb running right - if it will run and perform alright with the servo disconnected then there is an air leak in the servo or servo feed pipe. Check the servo vacuum feed pipe for cracks and holes.
If there is a leak at the servo replace or obtain a service kit and repair.

[Sleeper]

Kevin
There are many permutations but on the majority of servos,the final connecting piece to the servo Vacuum can is a non-return valve and on others it isn't , some have in-line valves.

John