Sudden drop in braking power on series 300 110 defender

HI everybody, I hope you guys can help me out. My landy has been stood for a little while during a time when I was travelling. Now that I'm back it started first time, is running well however all of a sudden I have lost braking power.
The brake discs were a little corroded from being stood but are ok, I think that there is a problem either with the servo or vacuum pump.

After revving the engine during running the brakes appear to be ok, but the classic sign something is not right is that when I start the vehicle the brake pedal doesn't get easier, or drop a little as the servo should do.

so I have some questions that I hope that you can answer for me.

1. How much vacuum should the pump be creating. it is not the easiest question to answer I dare say, but when the engine is running, after taking the pipe off the servo, and revving the engine, the pipe barely has enough vacuum to suck onto my hand, there is some vacuum but not a lot. How can I measure this?

2. Before I eliminate the servo failing, is the vacuum pump easy to maintain or is it something that I change?

I may have further questions but for now if you guys could help me out with this I would really appreciate it.

Thanks

Kenny

There should be enough vacuum for it to stick to your hand.300 vac pumps known for giving up now and then. Change it.

Check the pipe first - they can collapse internally and 'suck' themselves shut.

tottot said:

There should be enough vacuum for it to stick to your hand.300 vac pumps known for giving up now and then. Change it.

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Agreed. IME they might last about 80K miles if you're lucky. They canbe fixed, but it ain't worth it. Avoid the cheap ones - unless you like doing the job

boguing said:

Check the pipe first - they can collapse internally and 'suck' themselves shut.

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+1 - pipe can delaminate - check for vacuum at the flexi "out" of the pump ( which, of course is actually the input - cos its not really a vacuum pump - more of an exhauster.....)

Simple test for the servo is, with engine stopped, and brakes pressed a few times to empty the servo, (then) start the engine with your foot on the brake pedal - if its all working properly, the servo will pull the pedal down, away from your foot.....

^^^ Wot he said