Vacuum pump stiffness (?)

[Lightyear]

Pulled the serpentine belt on the Burb to R&R the p/s pump. I noticed the vac pump pulley is quite stiff to turn by hand. Is that normal? I have also noticed on a recent 500 mile trip that after about 250 miles highway cruising, the truck developed almost a cackle, and felt like there was some degree of drag on the engine. All gauges were ok, fuel consumption in the low 16s at 65-70mph. Any comments out there?

Thanks all!

[Lightyear]

Forgot to mention I/ve gotten an intermittent P0236 code, but no SES light while this weirdness was happening.

[Burning Oil]

vac pump seems normal. Put a gauge on it to see that its pulling a vac.

[Lightyear]

Thanks for the tip...but here's a dumb question: Where do I put the gauge?
Thanks

[Lightyear]

While I was in there, found the harmonic balancer/damper going bad. It was making that slapping/knocking noise. Next project!

[DmaxMaverick]

Thanks for the tip...but here's a dumb question: Where do I put the gauge?
Thanks

Ideally, on the pump outlet. Otherwise, you can also connect to the wastegate solenoid (more easily accessible, on the line from the pump). If you see less than 22", definitely check at the pump, and compare the numbers. This will eliminate a damaged line possibility. While you're at it, if the pump is pulling 22"+, check the wastegate actuator line as well. At idle, it should be about 15" (it's PCM modulated, not on/off).

22-26" HG pump vacuum is healthy. Less is a failing pump or leak.

[Robyn]

When you rotate the vacuum pump, it should turn easily then get stiff, and then rock over the stiff spot and turn easy again.

These are a diaphram pump with a cam setup.

If your vacuum gauge wobbles a lot while the engine is running, the pump is shot.

These pumps will generally pull 26" HG at an idle and this will show a steady needle on the gauge.

If the needle wobbles, it means that the valves in the pump are leaking or the diaphram is failing

Missy

[Burning Oil]

While I was in there, found the harmonic balancer/damper going bad. It was making that slapping/knocking noise. Next project!

I have the Fluid Damper harmonic balancers for $405 + shipping.
Not on my site yet so PM me if interested.

[Lightyear]

Well, the vac pump is now one step down on the project list. When I R&R the balancer, do I need to change out the pulley as well, or is just swapping the balancer acceptable?

Thanks again, everyone.