Engine/Transmission (1998.5 - 2002) funny noise at startup and braking (vacum pump?)

[CRSmith]

It was 5deg this morning. When I started the truck, there was a groaning noise that got louder, vibrated the truck and the brake pedal when you turned the wheel or put on the brakes. This went on until I drove about 30 miles and the truck warmed up. Could this be the vacumm pump?

 

[poolguy]

check your power steering fluid. Mine did the same thing and it was low. As it warms it expands and the noise goes away. Good luck

 

[ntillm01]

Ditto the power brake/steering pump fluid. In these single-digit temps, none of the oils want to flow like they should. The noise you hear is air bubbles in the pump. It could be low because of the cold-contraction thing. I think, too, that because the fluid is so thick that it foams up in the pump.

 

[CRSmith]

Thanks. It looks like Valvoline Syn-Power is the stuff to use from searching.