2004 Yukon Denali Hydroboost Symptoms

[DrScottSmith]

All -

Latest issue with the Yukon...

Pretty substantial PS fluid leak. Return line was loose so tightened it but leak persists (now at box I believe).

Also - have always had the issues viewed below with Hydroboost. No visible leaks at HB unit itself. No brake fluid leaks. Brake fluid flushed and replaced about 5k ago.

When pushing brake pedal, listen for the sound of steering pump (that may be normal).

Video one below shows what happens when turning the wheel and when pushing the brake pedal.

Video two shows motion in the line to the HB unit moving as well as sound and HB unit itself moving up and down. The pedal has a kind of ‘bump’ about 7/8 of the way down, but pressing harder results in what happens in video 2 - nasty sound and you can feel vibration, etc in steering wheel at this point.

thanks all

-Scott

 

[rockola1971]

Is it wet on the underside of where master cylinder bolts to your Hydroboost? Been running the power steering pump empty or real low where it start making alot of noise? If you have been, remember that if/when that power steering pump goes that you will NOT have any brakes but emergency. Ask me how I know. I am still fighting a leak that I cannot find.
Here is what I have replaced so far: Gearbox (it was worn), power steering pump (it failed), power steering cooler and its 2 lines, line from gearbox to hydro boost.
What I ordered and am procrastinating to install: Hydro boost, line from hydro boost to power steering pump.

 

[DrScottSmith]

I feel like this may be the Hydroboost unit itself...but trying to get a better idea before diving in.

the PS fluid BHS gotten low but as soon as it makes noise (or before) I add fluid.

Everything still seems to work fine (power steering and brakes) but there is just a good bit of vibration in the steering that I don’t like.

 

[SnowDrifter]

Sounds like a worn p/s pump and the pressure relief valve triggering.

Not sure if the movement in the master is normal or not. Never seen mine under the hood before.

 

[DrScottSmith]

Ok got under there tonight and the leak is definitely from the bottom seal of the steering box where it attaches to the arm (can’t remember if that side is pitman or idler).

so I guess I will start there and see what happens.

will update. Thanks again all.