Thread: blank off 300tdi vacuum pump

Originally Posted by Didge

Thanks gents - bit the bullet and bought a new pump but not a Wabco one - supplier (Karcraft) won't use them anymore and they said the one they sold me is a much better unit (time will tell). Will install with the 2 gaskets to save the piston. I can't move the piston on the new pump but can do so on the old Wabco one but that's the one that barely provided any suction. I searched for a oil injector inside the pump housing area but couldn't see one. Will let you know the outcome later today - hopefully.
cheers Gerald

I bought a Bearmach from Karcraft probably 6 or 7 years ago as I refused to buy a Wabco and AFAIK it's still on the car.

Hi Rick & all, update is rather disappointing as the new pump does suck harder but no where near what I expected and the pedal only drops a little bit due, I hope, to vacuum. Next thing to check is the vacuum hose but I'm very certain that is leak free. Failing that and possibly seized calipers (which i haven't checked), I'm stumped.

Are you absolutely, positively sure the booster is ok?
You can tell me too bugger off, I can take it, but they are a problem with fatigue cracking.

Originally Posted by Didge

Hi Rick & all, update is rather disappointing as the new pump does suck harder but no where near what I expected and the pedal only drops a little bit due, I hope, to vacuum. Next thing to check is the vacuum hose but I'm very certain that is leak free. Failing that and possibly seized calipers (which i haven't checked), I'm stumped.

Originally Posted by rick130

Are you absolutely, positively sure the booster is ok?
You can tell me too bugger off, I can take it, but they are a problem with fatigue cracking.

Hi Rick, well it was only 60,000km ago that I replaced both the vacuum pump and servo (booster). I attached it to a vacuum cleaner (which quite surprisingly fit very well over the rubber grommet for the one way valve), and it certainly made depressing the plunger a hell of a lot easier.

Given that the average vacuum cleaner supposedly provides 20kpa of vacuum and the vacuum pump is supposed to dish out approx 75kpa = (10-12psi/-.8ATM/20-25inHg - from blknight's post) of vacuum (which I highly doubt) I figured a conservative way to test the servo would be to use the vacuum cleaner as it is around 1/4 of the strength the pump is supposed to provide.
This morning I did the test where you pull the hose off the servo and listen to the hiss as air rushes in but it was still disappointing - not too much hiss at all. I'll double check the hose itself and have another look at the servo but I'm pretty sure that is in good nick. I haven't really done much off roading since I replaced them (which is disappointing). I'll also double check the seal between the master cylinder and servo.

Originally Posted by Didge

...listen to the hiss...

With the vacuum pump connected to the servo and engine running stick your head in the drivers footwell to determine if there is a hiss coming from the servo on the other side of the firewall - hiss is air leaking into vacuum.