I'm pretty sure its the Vacuum pump but after replacing it with three different s/hand ones the problem still persists.
I have a Vacuum guage and am getting no vacuum on early morning start up. After one to two minutes (depending on which pump) the vacuum starts sucking.
Having at first tried two s/hand pumps I thought it can't be that and changed the servo, same problem.
As GSF have discontinued the replacemment pump the only way I can source a new one is from VW@ around £125.
I have no problems paying this but want to get some expert advice first,as If it doesn't fix it I am liable to set fire to the van.
Its deffinitely not a leak in the pipes or one way valve as when the pipe is removed even after leaving overnight, there is the sound of rushing air.....
It cant be the intermediate shaft as it drives the oil pump through the vacuum pump (I think).
could it just be that once these Vacuum pumps are left lying around they stop working properly?
Luckily the pumps I have purchased have been not a lot more money than the postage so I cant complain about that.
Can I be unlucky enough to have three plus my original pump inoperative?

the only thing I have not changed is the master cylinder, but I cant see that being intermittent.
many thanks Rob..............
ps. have also posted this on Brickyard.