Question about Hummer H1

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Have 2 Hummers ( both 1995) that have a Hydrualic 'boost' loss to steering when brakes applied. Steering power increases if I flip the throttle which allows me to turn the wheel when throttle is hit. Brakes also lose some power. Not noticiable at speeds over 15mph, only on slow turns. Fluid levels for both systems are normal and no leaks from the lines. Is there a proprtioner valve that controls pressure from the hydrualic pump that may have failed and if so, where would it be found ? Dennis

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At the back of the pump where the high pressure line attaches. I'm not saying thats your problem, but thats where the valve is. I think if you disconnect it, it should have full boost.

Posted on Aug 31, 2010

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1995 Chevy p30 chassis builds pressure and applies brake while moving or setting until you bleed front brakes


pressure build up in brake lines indicates a blocked compensating port in the master cylinder. The heat generated by brake operation is expanding the brake fluid which cannot return to the reservoir and so it is apply the brakes. If you have an ABS system on the vehicle have it checked out by an accredited brake shop for operation as well

Oct 28, 2014 | Cars & Trucks

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2001 Silverado 2500 HD Why Rear brakes don't work after I installed new hydro-boost power booster, master cylinder, calipers, and pads. I bled master cylinder before installing, and brakes beginn


Hello Patricia,

Have you checked the master brake cylinder reservoir for brake fluid loss?

I don't suspect the master cylinder as you have replaced it... but am more suspect of a leaking brake line or fitting which should have
been discovered when you had the system bled.

The only time I ever had a rear brake problem with a 2500 series Chevrolet was due to seized rear brake caliper guide pins...as your calipers are also new that is not your problem.

If your brake pedal feels spongy and travels to the floor board you have air in the system, a brake fluid leak or a failure in the power steering system, such as a broken hose, broken power steering pump drive belt, or failed pump, would result in a loss of pressure to both the hydro-boost and steering.

Find more information here:

. Hydro Boost Power Assist Systems Operation Diagnosis and Repair

Jul 23, 2017 | 2001 Chevrolet Silverado 2500HD

1 Answer

2001 chevy tahoe vacum hoeses for power steering


Hello! There are power steering fluid in/out hoses but no vacuum lines...It sounds as if the pump needs to be bled of air or the belt is loose...Belt should move about 1/2 to 3/4"...Bleeding is as follows...
Guru...saailer

    ImportantPower steering fluid level must be maintained throughout bleed procedure.
  1. Fill pump reservoir with fluid to minimum system level, FULL COLD level, or middle of hash mark on cap stick fluid level indicator.
  2. ImportantWith hydro-boost only, the oil level will appear falsely high if the hydro-boost accumulator is not fully charged. Do not apply the brake pedal with the engine OFF. This will discharge the hydro-boost accumulator.
  3. If equipped with hydro-boost, fully charge the hydro-boost accumulator using the following procedure:
  4. 2.1. Start the engine.2.2. Firmly apply the brake pedal 10-15 times.2.3. Turn the engine OFF.
  5. Raise the vehicle until the front wheels are off the ground. Refer to Lifting and Jacking the Vehicle in General Information.
  6. Key on engine OFF, turn the steering wheel from stop to stop 12 times.
  7. Vehicles equipped with hydro-boost systems or longer length power steering hoses may require turns up to 15 to 20 stop to stops.
  8. Verify power steering fluid level per operating specification. Refer to Checking and Adding Power Steering Fluid .
  9. Start the engine. Rotate steering wheel from left to right. Check for sign of cavitation or fluid aeration (pump noise/whining).
  10. Verify the fluid level. Repeat the bleed procedure if necessary.

May 03, 2012 | 2001 Chevrolet Tahoe

1 Answer

Power steering and brakes do not work when I returned from vacation


RECALL: 2003-2004 Hummer H2 NHTSA Campaign Number: 04V045000

www.nhtsa.dot.gov
Manufacturer GENERAL MOTORS CORP. Recall Date: 02/04/2004 Potential Number Of Units Affected: 68,875 Description SERVICE BRAKES, HYDRAULIC Summary CERTAIN SPORT UTILITY VEHICLES, PICKUP TRUCKS, AND PASSENGER VANS FAIL TO COMPLY WITH THE REQUIREMENTS OF FEDERAL MOTOR VEHICLE SAFETY STANDARD NO. 135, ?PASSENGER CAR BRAKE SYSTEMS.? SOME OF THESE VEHICLES WERE PRODUCED WITH AN OUT-OF-SPECIFICATION BRAKE HYDRO-BOOST HOUSING RELIEF VALVE BORE. Consequence CONSEQUENTLY, THE VALVE O-RING SEAL MAY FRACTURE. STEERING EFFORTS MAY BE SLIGHTLY INCREASED WHILE BRAKING OR PARKING. UNDER CERTAIN DRIVING CONDITIONS, A FRACTURED SEAL MAY REQUIRE A SLIGHT INCREASE IN THE APPLIED BRAKE PEDAL EFFORT TO ACHIEVE THE SAME VEHICLE DECELERATION RATE AS PRIOR TO THE SEAT FRACTURE. Remedy DEALERS ARE TO REPLACE THE HYDRO-BOOST RELIEF VALVE. THE RECALL BEGAN ON APRIL 26, 2004. OWNERS SHOULD CONTACT CADILLAC AT 1-866-982-2339; CHEVROLET AT 1-800-630-2438; GMC AT 1-866-996-9463; OR HUMMER AT 1-866-486-6376.

Jan 03, 2011 | 2003 Hummer H2

1 Answer

My brakes and power-steering are not working. The brake pedal is hard, but the brakes will not engage. The power steering was not working at the same time. It has brake fluid, but when I took the power...


Yes, your brakes are boosted by the power steering pump rather than by vacuum. I don't think it's air in the system. More likely your pump has failed, but you can try bleeding the pump. Here is a procedure from autozone.com:

Observe the following:
Use clean, new power steering fluid type only Hoses touching the frame, body or engine may cause system noise. Verify that the hoses do not touch any other part of the vehicle. Loose connections may not leak, but could allow air into the steering system. Verify that all hose connections are tight.


NOTE Power steering fluid level must be maintained throughout bleed procedure.

  1. Fill pump reservoir with fluid to minimum system level, FULL COLD level, or middle of hash mark on cap stick fluid level indicator.
    NOTE With hydro-boost only, the oil level will appear falsely high if the hydro-boost accumulator is not fully charged. Do not apply the brake pedal with the engine OFF . This will discharge the hydro-boost accumulator.
  2. If equipped with hydro-boost, fully charge the hydro-boost accumulator using the following procedure:
    1. Start the engine.
    2. Firmly apply the brake pedal 10-15 times.
    3. Turn the engine OFF

  3. Raise the vehicle until the front wheels are off the ground.
  4. With key in the ON position and the engine OFF , turn the steering wheel from stop to stop 12 times. Vehicles equipped with hydro-boost systems or longer length power steering hoses may require turns up to 15 to 20 stop to stops.
  5. Verify power steering fluid level per operating specification.
  6. Start the engine. Rotate steering wheel from left to right. Check for sign of cavitation or fluid aeration (pump noise/whining).
  7. Verify the fluid level. Repeat the bleed procedure if necessary.

Observe the following:



Use clean, new power steering fluid type only Hoses touching the frame, body or engine may cause system noise. Verify that the hoses do not touch any other part of the vehicle. Loose connections may not leak, but could allow air into the steering system. Verify that all hose connections are tight.
NOTE Power steering fluid level must be maintained throughout bleed procedure.
  1. Fill pump reservoir with fluid to minimum system level, FULL COLD level, or middle of hash mark on cap stick fluid level indicator.
    NOTE With hydro-boost only, the oil level will appear falsely high if the hydro-boost accumulator is not fully charged. Do not apply the brake pedal with the engine OFF . This will discharge the hydro-boost accumulator.
  2. If equipped with hydro-boost, fully charge the hydro-boost accumulator using the following procedure:
    1. Start the engine.
    2. Firmly apply the brake pedal 10-15 times.
    3. Turn the engine OFF

  3. Raise the vehicle until the front wheels are off the ground.
  4. With key in the ON position and the engine OFF , turn the steering wheel from stop to stop 12 times. Vehicles equipped with hydro-boost systems or longer length power steering hoses may require turns up to 15 to 20 stop to stops.
  5. Verify power steering fluid level per operating specification.
  6. Start the engine. Rotate steering wheel from left to right. Check for sign of cavitation or fluid aeration (pump noise/whining).
  7. Verify the fluid level. Repeat the bleed procedure if necessary.

Oct 24, 2010 | 2005 Chevrolet Silverado

1 Answer

Loss of brakes and steering


sounds like you've got a bad power steering pump. i'm not familiar with your vehicle, but some brake boosters run off vacume from the engine and others run off the power steering pump and it's called hydro boost. if you have the hydro boost type, this is most likely your issue.

Feb 09, 2010 | 2001 Chevrolet Silverado 2500HD

2 Answers

Power steering went out along w/brakes


Does it have a hydroboost brake booster? Is the belt still on the p/s pump? Have you checked the power steering fluid level? If yes and good to all, replace the Power steering Pump.

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1 Answer

I have a 1995 ford f250 with the 7.3L diesel. The vehicle makes a large sucking noise when cold, and the engine loses power. when the rpm's pick up, it regains power and drives well. Problem goes away when...


The problem is due to a lack of compression in the engine when the truck is cold, try using the engine block heater more, or allow more time for the truck to warm up.

Jan 02, 2009 | 1995 Ford F250

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