Cutting out when brakes applied

[Supertramp]

Just wanted to check I am on the right track...
When coming to a junction/traffic lights my bus has started cutting out. I first thought this was a carb issue/idling but if I'm stationary and the bus is idling, and I press the brakes, revs drop and it cuts out. So this would imply that the servo or something servo related is at fault?
What should I check first before assuming I need a new servo?

Thanks

 

[gvee]

Some kind of short on the brake light circuit.

 

[chad]

There was a thread about this on another forum recently.

It turned out, if I remember correctly, to be the wiring to the tow bar.

Not a lot of use if you don't have a tow bar fitted !

 

[subheatadey]

It sounds like the non-return valve to the servo or the brake servo itself

 

[Supertramp]

No tow bar and from everything I've read it's definitely servo related.
Now this non-return valve, where is this located? I've also read that I need to block off the hose at the servo end to check this is definitely the cause, which hose is this then and also can I just pull it out and block it off, nothing will come out and burn my eyes? :lol:
But seriously sorry for the silly questions, clueless when it comes to this stuff.

 

[chad]

The questions aren't silly - that's how you learn

 

[neilswheels]

'Usually' located in the engine bay. There should be a pipe coming from your left hand inlet manifold and running away from you thru the firewall. Between the manifold and there firewall there should be an inline valve.
Nothing will come out if you remove it, it just sucks air.
Fault could also be a leak along the length of the pipe, or at the servo, but valve is the easiest/cheapest place to start. If its the pipe, buy the proper stuff cos its reinforced to prevent the pipe collapsing with the vacuum.

 

[Supertramp]

So a bit of digging underneath the van and had my dad press the brakes while I was underneath.
There is definitely an 'air' nose coming from around the servo but can't 100% tell from where, or does the servo just make a nose when operating?

This 'boot' looks like it has a hole in and sounds like the area I can hear air, could this be it? Picture and video included:

VIDEO

 

[Supertramp]

'Usually' located in the engine bay. There should be a pipe coming from your left hand inlet manifold and running away from you thru the firewall. Between the manifold and there firewall there should be an inline valve.
Nothing will come out if you remove it, it just sucks air.
Fault could also be a leak along the length of the pipe, or at the servo, but valve is the easiest/cheapest place to start. If its the pipe, buy the proper stuff cos its reinforced to prevent the pipe collapsing with the vacuum.

Thank you.
Is this it:

 

[rallye dale]

Yes thats it

 

[Supertramp]

Cheers Dale.

Ok so I have it off:

Am I correct in assuming that if I blow through one end it should come out the other, but if I blow through the opposite end it shouldn't? I can blow through both ends of this.

 

[subheatadey]

Thats right one way only, you can get them easily enough just make sure you fit the new one the right way round

 

[kreemoweet]

Testing the servo vacuum non-return valve works much better if you suck on it, rather than blowing, the latter
frequently giving inconclusive results.

In any event, that valve will not be the cause of your problem. Since the engine stalls only when the brake
is actuated, there is almost certainly a vacuum leak at the valving inside the booster. A new or reconditioned
servo is the remedy. You can confirm by disconnecting the vacuum hose at the rear of the servo and plugging the
hose end. Your brakes will be very hard to operate, but the stalling-out should cease.

FYI, the instructions for installing that valve given in the Bentley service manual are incorrect: the arrow on the valve should
point to the engine, as indicated on the valve itself.

 

[Supertramp]

Testing the servo vacuum non-return valve works much better if you suck on it, rather than blowing, the latter
frequently giving inconclusive results.

In any event, that valve will not be the cause of your problem. Since the engine stalls only when the brake
is actuated, there is almost certainly a vacuum leak at the valving inside the booster. A new or reconditioned
servo is the remedy. You can confirm by disconnecting the vacuum hose at the rear of the servo and plugging the
hose end. Your brakes will be very hard to operate, but the stalling-out should cease.

FYI, the instructions for installing that valve given in the Bentley service manual are incorrect: the arrow on the valve should
point to the engine, as indicated on the valve itself.

Thanks for the information. I also sucked on the valve ( :msn4: ) and could get air through both ways so I've ordered a new one anyway.
Could there be any other leaks in the hoses that would cause my engine to stall when the brakes are pressed? I'm just trying to rule out all possibilities before getting a new servo.

Thanks again.

 

[Supertramp]

Further updates. Took the hose off the servo and blocked it up (a few table spoons of oil/fluid came out of this hose, should that happen?) and tested my brakes, no cutting out. Short run up the street and no cutting out, also my brakes don't feel any harder than they did going to Southwold and back, suggesting that it is indeed the servo at fault.

 

[StuF]

Pah I have done 3000 plus miles loaded up with no servo!
That's how I roll :msn4:

Sounds like your servo hasn't been working for a while!

 

[Supertramp]

Pah I have done 3000 plus miles loaded up with no servo!
That's how I roll :msn4:

Sounds like your servo hasn't been working for a while!

I agree. To be honest brakes didn't feel any different than my 69 with no disc's so I reckon servo has never worked.
Due to go to France in a week so servo might have to wait until after then :msn4:

 

[StuF]

Will be fine I am sure - am off to France, Belgium and Germany starting on Wednesday next week for a couple of weeks with the Wifelet! SPA here we come

No servo - No worries :msn4: