We have 3 trucks with the same issue: a 2003 Gmc 8.1L 3500 4x4 manual and we have changed the ps pump and the brake booster and the steering box and nothing has fixed the loss of brakes and ps when coming or entering a turn. Same thing happens to our 2005 Gmc 2500Hd 6.0L 4x4 and our 2006 Chevy 6.0L 4x4. Just wondering why and what we can do to fix it and if it's a common issue. Thanks Cody

happened out of the blue now? or bought it like this?>
yukon , or yukon xl1500xl or xl2500 ? i guess left own here.
check fuses
and scan the car.
I am sure the scans will fail with DTC, so scan it see what fails.
check PS fluid levels and
for PS hoses leaking,
check loose belts to PS pump pulley
or have real shop look at it??? auto repair shop, even ASE rated shops, USA??
guess 3, hydro-electric- steering option in place, ?and or.
got rear wheel steering option?
find the, RPO code tell what it is there read RPO yet? (as built list)

read the service manual here on steering, a very complex system
check it out.

https://eautorepair.net/Marketing/Default.asp

I think it is called the hydraulic brake booster. It is on the fire wall, drivers side.

Unless you have a power steering assisted brake booster more common with a diesel, you may have a new pump issue like the flow control valve in the pump or air in the system yet, check for air bubbles or a milky looking fluid and the correct fluid. Try in a parking lot out of the way of traffic to put in neutral while moving,rev the motor slightly and brake as you would when the PS assist stops,by revving the motor just off idle this will increase the PS pressure it should act normal if it's a flow control issue and if the pump is capable of producing the correct pressure.

Does the air pump or power steering feel
seized or tight?

The belts came off for a reason

Lingo is o.k., but I think you may be confusing power steering with power brakes. Power steering has no master cylinder (brakes do) and no power booster (brakes do). The power steering pump is mounted on the front of engine and run by the fan belt or the serpentine belt. The p/s hoses are 2- a pressure line and a return line, and run from the pump to the steering box or to the rack and pinion steering gear.
It just sounds like you have a brake fluid leak at the master cylinder. If it is, you need a new or rebuilt brake master cylinder.
Good luck. Post back for more.

The brakes and the Power Steering are two different systems and two different problems. The brake problem is going to be a caliper or master cylinder issue which maybe a Vacuum issue if the Power Booster hose is leaking or disconnected from the master cylinder. The power steering is going to be low fluid in the power steering pump, faulty power steering pump (Obvious if you were hearing a whine that got louder as you turned the wheels, or the Power assist piston that connects to the tie rods.

diesels do not have conventional vacuum operated brake boosters. i am not sure what chrysler calls there system, but i believe it is similar to the gm hydroboost system, in which case pressure is created by a pump integral to the power steering pump gives you your assist, and fed to an accumulator on the fluid booster near the master. be very careful when tinkering when these systems, as they can have very high pressures in them even when the car is not running. are you experiencing any steering issues at the same time? check your fluid levels (PS fluid will effect operation) and all the associated hoses and lines, go from there. good luck!

First check any vacuum line going to the brake booster. The P.S. is assisted by the power brake booster. Check for leak or disconnected line.

Second, check P.S. oil level

Third, check the condition or your serpentine belt and how it fits to your P.S. pump pulley

These checks have to be done first, but my guess is that your P.S. pump is bad. If you make the decision to replace it, make sure you have the correct replacement part. I have been told that auto parts store have difficulties to find the correct match as long you don't put yours on the desk.

Not a tough job to replace.
No you don't have to bleed the new installation. Just fill with P.S. oil, start the engine turn your steering wheel from one extremity to the other and vice versa few times. Do not insist to push it to the limit when at extremities.

Stop the engine, check reservoir oil level and it should run ok
hope it will help
Dan

you have hydralic brake system.control by the power steering pump.check power steering pump fluid if low add.if fluid level good have the dealership check it out.your booster or power steering is going bad.

I'd bet you dollars against donuts that when the new MC was installed it was left with air in the lines. Bleed the brake lines to get that air out of there, and I suspect your brakes will firm up nicely.