My '93 has the vane style pump and it seems weak.
Has anyone had one wear out?

 

my older dual diaphragm lost one di' and went down 10hg's, making the brake booster less efficient, check your vacuum at the pump, also pinch off the booster to make sure its not leaking, if the pump is weak, they are rebuildable, you want to see around 20hg's when running after warmed up.

 

Well, Gould sells vanes and seals, so I would say there must be at least a few wearing out, otherwise he wouldn't bother.

Check them out, fixinrams.com

 

Since these vacuum pumps are, as stated, vane pumps, there is always the possibility that the vanes have worn out. But I highly doubt it.

I'd order a reseal kit and toss it in. Once it's apart you'll know for sure if the vanes need replacing.

 

got a '93 W250; had same problem - ordered seal kit from Cummins. Vane condition was not prominet: Cummins 6B5.9 motor.