Hi,
Following from a posting of the same title dated 30th Jan and the useful replies, I did my best to improvise a test for the items on the vacuum circuit for leakage by plugging of outlets and running the car stationary with a vacuum guage attached to a small T-piece inserted in the circuit.
By sucking and holding for some seconds, there seemed to be no significant diaphragm leaks on the EGR, manifold or wastegate actuators and plugging the outlet to various items like the feed to the combined solenoid pair for the EGR and manifold valve only made a very small difference. I had no item to break into the line to the brake servo but the old method of exhausting the vacuum by multiple pressings of the foot pedal until the vacuum assistance had gone and then re-starting the engine with my foot on the brake pedal took only a few seconds at idle to pull the pedal down and restore the servo assistance.
The first reading taken was directly from the vacuum pump alone and that looked fine at 20" - 25" Hg but later, when repeated, it was not nearly as good, say 10" - 15" Hg. So I assumed the hot oil was not making as good a seal. Decided to take the vacuum pump apart and found lots of scoring in the die cast end face (away from the lid), seriously bad and uneven wear on the rotor face that mates with that surface. There were a few scores in the sidewalls and matching damage to the rotor tips which held a few ally particles embedded in them to continue the scoring process.
So the first thing to do will be to replace the pump. Was quoted 216 Euros retail. That's about 125 UK Pounds. There is no low oil level (notoriously difficult to measure on the Vectra) and since I have been having trouble for some time, the damage may have been started before I got the car and has just been progressing.
Just out of whimsey 'cause the pump is knackered, I smoothed down the rotor edge with the main damage using plate glass and wet and dry abrasive paper, same with the ally face of the pump body and main driveshaft that fits inside the body and holds the rotor. Good dial calipers were used to measure things. (Well you should have seen the clearances before doing anything to it!) Teated the end seals to a similar style clean up, cleaned off all the residue very thoroughly and rebuilt the pump. Unfortunately, it would have required a milling machine to do anything to the internal scored bottom face. It was done in the style of renovating an old motorcycle gear-type oil pump - well it's knackered anyway!
I drove about 50 miles with it yesterday and will have to use it until the new pump arrives. The vacuum is noticeably better at the guage, even when hot, and no EML came on - but no, I am not deluded into thinking I have cured it anything other than temporarily. The scored end face will continue to damage it.
Glad it's an interest - wouldn't like to have paid for my time on it. If necessary, will re-look at the other items on the vacuum line after fitting a new pump. They are probably within the capabilities of a good pump.
Thanks again for all the advice - it is at last getting dealt with and was irritating me for some time.
Tony.