Vacuum pump replace / repair???

I am diagnosing an underboost on a 2000 TDI Jetta. Symptoms are underboost code, hard brake (no vacuum boost), and very low vacuum measured at the N75 out line.

I have replaced the vacuum lines and the rigid tube from the pump to the brake booster. The vacuum lines were in poor condition and there was a crack in the rigid tube to the brake booster. To my dismay there is still very low vacuum. Once again, there is no brake boost, braking is very hard.

I am now trying to explore the possibility that the vacuum pump has failed. I can't seem to find any information on the vacuum pump failing and can't find a replacement online or a rebuild kit. I've searched these forums and can't find anything.

SO... does anyone have experience with this? Has anyone had to replace the vacuum pump? Do they fail with any frequency?

I would put a gauge directly on the pump thereby removing any possible leaks in the brake booster itself.

Yeah, I guess that's a good idea. I was going to measure it from the nipple off the check valve (eliminating everything else BUT the booster) but I guess that could still be ambiguous. I'll have to figure out how to adapt the mighty vac to the pump directly.

The reason you find so little information is that the internally lubricated vacuum pump (aka wet pump) fails very seldom. That's why people are usually told to check the lines, check the solenoids, check the black reservoir, check the brake booster line. Once in a very long while, a vacuum pump does quit though, so if everything else is OK, maybe it really is the pump.

vaccum pump

Wher can you get a vaccum pump, other than a dealer ? I'm in need of one for my 1998 Beetle, and am having a hard time finding one, either new or used.

Dealer for me. Ouch

Both Boraparts.com and 1stvwparts.com have them and I'm sure they are much better priced than the stealership. Just under $150 at bora