2nd Gen Non-Engine/Transmission Hydro-boost

[DValentine]

Well it seems that I have a bad booster. Both steering and braking are compromised. If I use the brakes the steering "locks up". I don't see any leaks. The peddle is hard, and with the engine shut off it has little or no reserve braking capacity.



Any one else have any issues with this system? I replaced the steering pump last summer at the time I replaced the vacuum pump seals.



I don't know how to diagnose. I am just going to start replacing parts and see what happens.



Dave

 

[jelag]

I'm confused with what you've said... you say that both the brakes and power steering are an issue... if so, do you have a brake circuit and power steering system powered by hydraulic pressure and the vacuum system has no effect... .

If on the other hand you have a vacuum booster it works the brakes, dash and AC vents and that's about it... . but the vacuum booster has no effect on the power steering...

If in fact you have a vacuum booster for the brakes, you need a vacuum gauge to test the system and it should see 25-27" of vacuum for the booster and brakes to work correctly... and on this old of a truck, you might have nothing but a bad vacuum leak. .

 

[Nigel]

Dave

If your 98 is a 12valve I believe you can turn your idle up a little bit to see if that helps. I remember reading about this a few years ago here and I am sure it applied to 12 valve trucks.



Nigel

 

[DieselDoghouse]

Jelag - just as info DV would NOT have ANY vacuum function related to brakes or steering…that was earlier vintage. Our trucks have a 'mini hydraulic' system powered by the P/S pump where the hydroboost functions as a hydraulic brake enhancer but with a 'power beyond' port that supplies the steering gear. So yes - stopping ranks above steering. With this system fault anywhere from the P/S pump, screens, lines down to the end devices could be at the cause. You are however correct that vacuum runs other stuff: HVAC controls, 4WD motor, Cruise… and thats it!. DV: alot of threads here on the hydroboost and its many malfunctions. I understand you can send it out for rebuild but its definitely not a DIY job. If you're facing a HB R&R I feel your pain. I started suspecting high heat was affecting seals in mine so when replaced I resorted to the old frame rail cooler on the P/S gear return line to try and preserve things.

 

[DValentine]

Thanks guys. After I posted, I went into the archive. I found some things. Led me around to the where I was before. I took the easy road. I pulled out fluid from the PS tank, to see how the fluid looked. Although I replaced it last summer, I think that the ps pump is to blame. The fluid is dark. The pump effort seems to be based on RPM and comes and goes. I will keep on it. Thanks for the replys.

Dave

 

[DValentine]

So, after reading and researching the power steering pump mods, pressure seems to be the problem. I have no dirt in the screen, and have checked the parts. The system works good when I first fire up the truck with new fluid. After the fluid warms up, 5 minutes both steering and brakes fail to work at idle. They work OK with the engine reved up. I am at a loss as to why I don't have the pressure at idle.

Any thoughts?

 

[DValentine]

I ran the truck 300 miles yesterday, so the system should have purged the air. Still acts funny after the truck has sat for a few hours.

 

[Bob4x4]

Unfortunately the only fool proof test requires a Pressure/flow meter. Not many shops will have one on hand. Here is a lil help on the flush procedure

FLUSHING POWER STEERING SYSTEM

Flushing is required when the power steering/hydraulic booster system fluid has become contaminated. Contaminated fluid in the steering/booster system can cause seal deterioration and affect steering gear/booster spool valve operation.



Raise the front end of the vehicle off the ground until the wheels are free to turn.

Remove the return line from the pump

NOTE: If vehicle is equipped with a hydraulic booster remove both return lines from the pump.



Plug the return line port/ports at the pump.

Position the return line/lines into a large container to catch the fluid.

While an assistant is filling the pump reservoir start the engine.

With the engine running at idle turn the wheel back and forth

NOTE: Do not contact or hold the wheel against the steering stops.



Run a quart of fluid through the system then stop the engine and install the return line/lines.

Fill the system with fluid and perform Steering Pump Initial Operation.

Start the engine and run it for fifteen minutes then stop the engine.

Remove the return line/lines from the pump and plug the pump port/ports.

Pour fresh fluid into the reservoir and check the draining fluid for contamination. If the fluid is still contaminated, disassemble and clean the steering gear and flush the system again.

Install the return line/lines and perform Steering Pump Initial Operation.

 

[Bob4x4]

POWER STEERING FLOW AND PRESSURE







1 - TUBE

2 - ADAPTER FITTINGS

3 - ANALYZER

4 - GAUGE HOSE





The following procedure is used to test the operation of the power steering system on the vehicle. This test will provide the gallons per minute (GPM) or flow rate of the power steering pump along with the maximum relief pressure. Perform test any time a power steering system problem is present. This test will determine if the power steering pump or power steering gear is not functioning properly. The following pressure and flow test is performed using Power Steering Analyzer Tool kit 6815 and (Analyzer With Tube and Adapter) Adapter Kit 6893.





FLOW AND PRESSURE TEST

Check the power steering belt to ensure it is in good condition and adjusted properly.

Connect pressure gauge hose from the Power Steering Analyzer to adapter 6826.

Connect tube 6825A to Power Steering Analyzer test valve end.

Disconnect the high pressure hose from the power steering pump.

Connect the tube 6825A to the pump fitting.

Connect the power steering hose from the steering gear to the adapter 6826.

NOTE: If fluid leaked from the steering system, it should be filled to correct level prior to starting the engine.



Open the test valve completely.

Start engine and let idle long enough to circulate power steering fluid through flow/pressure test gauge and to get air out of the fluid. Then shut off engine.

Check fluid level, add fluid as necessary. Start engine again and let idle.

Gauge should read below 862 kPa (125 psi), if above, inspect the hoses for restrictions and repair as necessary. The initial pressure reading should be in the range of 345-552 kPa (50-80 psi).

Increase the engine speed to 1500 RPM and read the flow meter. If the flow rate (GPM) is below specification, (refer to pump specification chart for GPM) the pump should be replaced.

CAUTION: The following test procedure involves testing maximum pump pressure output and flow control valve operation. Do not leave valve closed for more than three seconds as the pump could be damaged.



Close valve fully three times and record highest pressure indicated each time. All three readings must be above specifications and within 345 kPa (50 psi) of each other.

Pressures above specifications but not within 345 kPa (50 psi) of each other, replace pump.

Pressures within 345 kPa (50 psi) of each other but below specifications, replace pump.

Open the test valve and turn the steering wheel to the extreme left and right positions three times against the stops. Record the highest pressure reading at each position. Compare readings to the pump specifications chart. If pressures readings are not within 50 psi of each other, the gear is leaking internally and must be replaced.

CAUTION: Do not force the pump to operate against the stops for more than 2 to 3 seconds at a time because, pump damage will result.



PUMP SPECIFICATION ENGINE RELIEF PRESSURE ± 65 FLOW RATE (GPM) AT 1500 RPM

1500 series 11032 kPa (1615 ± 65 psi) 3. 1 - 3. 5

2500 & 3500 series 12400 kPa (1800 ± 50 psi) 3. 5 - 4. 0

 

[GAmes]

Did you replace the PS pump with one of the rebuilds that auto parts stores sell or a new one. After going through a half dozen of the bargain rebuilds, some of which had lifetime warranties, I finally bought a new one from mopar4less and haven't had a problem since.

 

[DValentine]

Yeah, GAmes, I saw that is the post on PS steering fixes and was going to pm you about that. I can't remember what steering pump I got at Napa. I will have to look at the receipt. I am close to your conclusion... go with new. I just don't have much time to be down right now.

Thanks for the responses, folks.

The thing that I can't figure out it why the system works when I first fire the truck up, with new fluid in it. It sat all night and shouldn't have had any air in the system to my understanding. But, when fired up cold this A. M. I had no steering until middle RPM.

Thanks again,

Dave

 

[GAmes]

I had to replace my booster a few years ago and IIRC the symptom was it puked the PS fluid out when I shut off the engine. It sounds like your NAPA rebuild has failed if you only have power at higher RPMs. When I finally bit the bullet and ordered a new pump it was only about $70 more than a rebuild. You may as well get a new seal kit from Cummins while you are at it.



I just went past Laurel on Friday, stopped at the Billings Cabela's, and drove into the snow showers up in the hills. Snow in May..... unreal.

 

[DValentine]

Did the seals last summer, when I put on the reman PS pump. Yeah, we have had a cold spring.

 

[GAmes]

The thing about seals is when you remove the sealed part and install a new part they tend to fail. It has had time to wear a little, and the rubber has had a year to get brittle. For $11 and 15 minutes, why not replace it?

 

[DValentine]

Drove the truck for something like 500 miles. The brakes and steering finally started to work at idle. I can't figure it out. Fluid level was fine. The systems would work fine above 1500 RPM. Now it just works.

I don't understand things sometimes.

Dave

 

[SMorneau]

FWIW, I replaced my ps pump with a NAPA rebuild years ago and it has never given me a problem.