Engine/Transmission (1998.5 - 2002) Vac.pump..maybe?

[BoeingDiesel]

I'm getting a really strange (intermittent) noise in my 99'. It's almost like a low pitched groan and is most noticeable when pulling away from a stop. Strange thing is; the sound stops immediately when I apply light brake pressure and comes right back when I release the pedal. Pads and shoes are brand new so I'm sure that's not the issue. Also, new rotors, bearings, etc. I'm kind of wondering if it could be a failing vacuum pump and/or P. S. pump?? Fluid level is perfect on the PS pump and connections to the vac. pump look o. k. and the heating /cooling vents are working properly. Any ideas or suggestions are greatly appreciated.

thanks

gregg

 

[hsmith]

Your truck is hydraboost, operates by power steering pump instead of vacuum. These units have a bad track record of leaking. Check your ps fluid level. If ok, may be a weak ps pump. Don't think you would ever get a groaning noise from the vacuum pump. All it supplies is the hvac and cruise servo.

 

[BoeingDiesel]

Thanks hsmith. I checked the fluid level in the PS pump a few minutes ago and the reservoir was full up to the hot level. That doesn't seem right if there is a cold line on the dip stick. I checked for leaks, inside and out, and there are none. Anyhow, I'm driving the truck back to LAX this AM and see what happens.
thanks again.
gregg

 

[Dieseldemon]

Change the PS fluid and that should take care of it