05 Denali - Power steering loses assist at slow speeds when hot

[Brake_L8]

I've done a bunch of Google-fu and am not finding a ton of conclusive information, so was hoping some of you could provide insight.

2005 Yukon Denali, 134k.

I had the steering box replaced a few months ago due to excessive slop and leaking. All was well for a few thousand miles, and now I have two issues.

My P/S pump is starting to whine at idle and will whine at low speeds when the truck is cold. Whine changes with RPMs and goes away once the truck is warmed up and driven a bit. I figure the pump may be on its way out, I'm 90% sure it's original to the truck.

The bigger issue I'm starting to experience is that after the truck gets warmed up, steering input at low/no speed (i.e. pull into parking garage at work, stop, put in Reverse and back in to spot) takes a significant amount of effort.

Effort will be reduced when I start rolling a few feet, but it's markedly heavier compared to how easy the steering is on a cold start when I back out of my driveway.

I found this thread and it looks like there is a pressure control valve that needs replacing.

Not scared to turn a wrench, but I'm entirely unfamiliar with this whole "Hydroboost" steering/brake setup so I want to triple-check before I go about mucking in the engine bay.

Thanks!

 

[Freedom Motorsports]

It is indeed possible that you need a new pump, but to attempt to fix it on the cheap with about 30 minutes of work, check out the thread below and see if fully flushing the system will help it out.

http://tahoeyukonforum.com/forum/showthread.php?t=38353

 

[Brake_L8]

It is indeed possible that you need a new pump, but to attempt to fix it on the cheap with about 30 minutes of work, check out the thread below and see if fully flushing the system will help it out.

http://tahoeyukonforum.com/forum/showthread.php?t=38353

Good advice, thank you. I'll give that a shot (maybe tonight if I'm not too lazy) and see how things go...

 

[TheAutumnWind]

It is indeed possible that you need a new pump, but to attempt to fix it on the cheap with about 30 minutes of work, check out the thread below and see if fully flushing the system will help it out.

http://tahoeyukonforum.com/forum/showthread.php?t=38353

Thanks for sharing. I had been planning to do this @ some point.

 

[Brake_L8]

Update - while I'm still positive the system needs to be bled, I checked the level of fluid in the PS reservoir today and it was low. Filled it back up and my pump quieted down a lot, and steering effort/braking effort was consistent the whole way to work.

Guess it's time to look for leaks. The steering box is new as of this February but there seem to be some other common failure points in the Hydroboost system.

 

[Brake_L8]

Another update. Looks like both lines that run off of the Hydroboost unit (the hard lines that turn into soft lines ~6" down) are leaking. The hard lines are dry but the soft line bits are damp, and everything below them is really wet.

I think I need #6 here:



but not sure what the other line is. Any help?

The two hard/soft lines that appear to be leaking are the ones circled in red here: