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When we apply the brakes, we lose power steering. Power

When we apply the...

When we apply the brakes, we lose power steering. Power steering works perfectly while driving until we hit the brakes

Mechanic's Assistant: When was the fluid last checked? Have you heard any whining noises while turning the wheel?

We topped the fluid off yesterday and still have the issue. With the wheels locked in either direction, there is a whine like you typically hear

Mechanic's Assistant: What is the model/year of your GMC?

2007 GMC Sierra 2500

Mechanic's Assistant: Are you fixing your Sierra yourself? What have you tried so far?

Yes we have our own shop and work on everything but vehicles. We work on our shop trucks as we just put a new transmission in this truck

Mechanic's Assistant: Anything else you want the mechanic to know before I connect you?

I pulled the return line of the hydro boost and I have fluid coming out of the nipple the return line connects to Other than that I think that is it

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Answered in 10 minutes by:
3/27/2018
JFN1
JFN1, ASE Certified Technician
Category: GMC
Satisfied Customers: 5,694
Experience: GM Master Technician
Verified

I've never run into this, but since the booster gets hydraulic pressure before the steering gear, it seems to me that the pump itself is suspect.

There are tests that can be performed, but they require a specialized power steering pressure/volume tester. What you're describing is a pump that can't keep up with the hydraulic demand when the booster is functional, and since there is a bias to booster before steering, I think the pump is the component at fault here.

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JFN1
JFN1, ASE Certified Technician
Category: GMC
Satisfied Customers: 5,694
Experience: GM Master Technician
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