how do I know if the brake servo is working properly?

[ronmidg]

warmed engine no problem, cold idle in current conditions when the tickover is very slow can feel the pulse through the pedal, and if the engine stalls the servo is gone in seconds. does have non return valve fitted, but only have one barrel tapped for vacuum. The nrv looks like a one way discourager rather than a actual valve, can see right through the middle, so guess its bound to decay at some rate, but how fast should it be? wondering about servo corrosion and leaks and how to tell the difference. Are there nrv with a moving part that actually seals when the pressure reverses?

 

[dubdubz]

not sure on all your questions but mine has 3 nrv's one nr the servo - one in the middle and one nr the manifold....one manifold tapped here too. passed mot - not exactly sure how you can test...let me have a look in my bentley manual....

 

[froggy]

To test if the servo's working (or if you've got a leak) press the pedal fully with the engine off, hold the pedal fully pressed and then start the engine, the pedal should now move even more, if not then the servo is not working.
With the engine running listen for air leaks this will indicate a split pipe in the servo system somewhere.

 

[ronmidg]

To test if the servo's working (or if you've got a leak) press the pedal fully with the engine off, hold the pedal fully pressed and then start the engine, the pedal should now move even more, if not then the servo is not working.
With the engine running listen for air leaks this will indicate a split pipe in the servo system somewhere.

Lines are new, servo works, and the foot on the brake test when starting the engine is good, cannot hear any leaks. How good is it supposed to be? I wonder if I have compromised system by only using one cylinder to create vacuum, or is it the nrv which is not a valve, or is there a leak in the servo not enough to stop it working when the engine runs, but loses vacuum quickly when the engine stops?

not sure on all your questions but mine has 3 nrv's one nr the servo - one in the middle and one nr the manifold....one manifold tapped here too. passed mot - not exactly sure how you can test...let me have a look in my bentley manual....

I have just one valve at the engine end, so will add another next to servo and see if theres a difference, rang round GSF, Halfords and Unipart and dont have anything, so have ordered a black and yellow one from heritage, different shape to the little black cylinder I have at the moment, theres a chance it works differently.

 

[froggy]

Guessing it the non return valve which isn;t a valve, replace this and everything should be ok

 

[ronmidg]

new valve arrived, black one end and yellow the other, can blow thru one way only which is probably a good feature for a nrv. now to brave the sub zero to fit.

 

[lard]

new valve arrived, black one end and yellow the other, can blow thru one way only which is probably a good feature for a nrv. now to brave the sub zero to fit.

Same as mine - black and yellow and can blow only one way - also have the end manifold tapped and it works well, can definitely tell the difference between servo assisted and non-assisted braking!

Best of luck in the cold - have just walked the dog and it's freezing!!!