Power Steering Systems, Remote Reservoirs &
What Breaks Power Steering Pumps
© Copyright 2000 - 2012 Chuck Kopelson 03/05/2003
Updated August 22, 2016
In a conversation I had with AM General I asked why they had gone to a Power Steering Pump with a remote reservoir? They told me that the standard pump with the reservoir set down low collected dirt that would get into the pump clogging a check valve that would cause the pump to seize and break the shaft. Locating the reservoir up high out of the dirt helped alleviate the problem. The photo on the left shows a pump with a broken shaft. If you do a pressure test, your pump should develop 1400-1500 psi.
If you want a sure shot way to break the pump get your engine tach'ed up around 1800 RPM and quickly crank the steering all the way to the right (or left) steering stop and nail the brake pedal all at the same time. The shaft may only last for a second!
Remote reservoir parts - pump 6003042 100.00 - Reservoir 6002107 33.00 - Cap 6002106 6.00
Remote Reservoir Setup. I had to make a mounting bracket for the tank.
The hose is 1" OD 12" long with 2 hose clamps to fit. When you get the pump etc just match up some hose. There is no pressure on the hose. The other low pressure hoses are 3/8" power steering hoses. The high pressure hoses are a dealer part but can probably be crossed with other vehicles since this is a generic GM pump.
The mounting bolts to the mounting bracket on the engine. The piece of steel is 1/4" thick, 1" wide and 6" long with 2 holes 3/8"? or 7/16"?drilled to fit the existing bolts. You can probably get a piece of steel at a Home depot or a Lowe's store. We may have welded a piece of metal on the tank.
Don't Assume Anything:
I received an email from a Hummer owner in Slovakia, Europe in 7/2016. This story illustrates that you can't assume that a butcher mechanic hasn't been working on your truck. The thing to take away is flow is everything in a PS system. All the hoses are part of the flow. Remove every hose and check the connections to make sure they are correct. Here's what happened..
I went wheeling, got stuck a bit, with the wheels turned fully to the left I needed to hit the gas to dig out.
Got out and everything was fine. In about 20 yards or so I needed to make a sharp turn while holding the brakes
and suddenly I lost my steering and brakes. I had to rev the engine to build the pressure in the system.
When I came back from the trail I thought to myself no big deal, the pump is worn, it has some miles....
I replaced the PS pump with an older but known good one, bled the whole system - I think I did it properly (at least 30 wheel turns, pedal down etc..., no air, no bubbles, no foam. Only a second or two after starting the engine the PS shaft broke causing the PS pulley to get loose and eat my serpentine belt.
Replaced the pump with a new after-market one and now i have the following issue:
I have a 2000 H1 6,5 turbo diesel.
Recently my PS pump went bad. No steering, no brakes.
The shaft with pulley got stripped inside the pump
Replaced with a new one, bled the system as per FSM
Started the engine - still no brakes or steering assist.
Now I think that the new pump has the same issue because when I remove the serpentine belt i can turn the PS pump pulley with almost no resistance and I do not have ANY flow from the hose which goes from PS pump to hydro-boost.
While I think the new PS pump is bad I don't want to install another new one without testing the hydro-boost some way because I have a concern that it will damage the new pump.
Today I did a small pressure test with my home made tool made with a high pressure gauge,
some hoses, a high pressure oil pump (actually a tractor hydraulic/steering pump driven by a small motor)
and a couple of shut off/ bypass and relief valves. It definitely looks like a hydro-boost issue because there is almost no return line flow from the unit. It also needs extra high pressure to make it work and it pulses back to the HP line.
Per your recommendation, I have replaced the PS pump and hydro-boost units with brand new original AMG parts.
Now when I press the brake pedal I have steady flow from the hydro-boost return line and the brake assist is working properly. The power steering still doesn't work. There might be an issue in the power steering gear, but I do not know where.
I think finally found the PS culprit.
The previous owner replaced the pressure hose which goes from hydro-boost to the PS steering gear with a custom made hose. During the replacement he damaged the hose seat inside the PS gear. Instead of repairing it properly he just stacked aluminum washers into the hole and used some weird screw-in coupler instead of a proper hose fitting.
This could have caused a flow restriction in the inlet port of the PS steering gear. My earlier tests showed there was flow but evidently not enough which mislead me in my first diagnoses. It's possible this restriction could have caused the PS pump to build up excessive pressure in the system which is why the hydro-boost and PS pump were damaged.
So now i need to remove the steering box and replace the hose seats and hose. I hope that helps because new gear is another fortune to buy.
I removed the steering box and discovered that a small check valve in the inlet port was damaged. it was jammed together and broken in 3 pieces blocking the flow.
The check valve in the inlet port of the steering gear should allow the fluid to flow only in one direction - into the gear. The broken valve restricted the flow of fluid into the steering gear killing the power steering. This also meant that there was little fluid returning to the PS pump. This could have caused a rise in heat and pressure taking out the PS pump. When installing the new check valve the shop manual calls for pressing it in using the old PS hose end. Since I didn't have the proper hose in the first place I had to fabricate a small 3" tool with a diameter a bit bigger than the PS hose seat with a tapered end. The valve goes in easy but it's quite deep into the PS gear and needs to be fully and evenly seated. I was able to lightly tap the valve in with no problem.
Make sure you route the pressure hose correctly. You need to thread it onto the hydroboost and PS gear first. Then check to see that the elbow at the gear side is pointing front-left. Tighten the hydroboost side and then the PS gear side.
We examined the hydroboost unit that was removed from the truck and found a piece of the check valve stuck inside.
After-market Steering Pump Setup:
Some owners are using a PSC 1405 pump (153.00) The 1400 series is a modified pump for more flow while the 1305 is a 'basic' pump. PSC recommends the 1405 for the H1. You NEED to make sure that you select the "hydro boost option" with the pump. They also sell a reservoir with a built in filter (SR100 122.00).
2000 Static Steering Issue
The "static steering" issue is found only on 2000 models for some strange reason. I have only heard of a few cases but enough that AM General was involved. A customer at Malmstrom Hummer had the issue and planned to sue AMG if his truck wasn't replaced. Basically, there is a complaint that the truck is hard to turn - even while driving - and in some cases it feels like there is no power steering at all. The entire steering system was replaced (pump, box, steering shaft, and lines) and it still isn't right. It turns about half way and then it feels like it is fighting you and will not turn lock to lock. AMG and they said it is a static steering issue a few trucks have had which is prone to 2000 models. There is no known fix.
Trouble Shooting Your Power Steering
First you should isolate the condition as being hydraulic or mechanical in nature. Lift the front of the truck just enough to allow you to turn the steering wheel with the engine off. The Hummer steering is 3-1/2 turns, lock-to-lock. If the problem is still there, then it is mechanical, probably a bad steering shaft joint. Greasing these sometimes fixes the problem but not always. There is a splined slip / sliding joint in the steering shaft. If it is seized up, that may cause some pretty weird things to happen in the spool valve of the steering gear.
I've also run across a binding steering wheel. In my case a Momo wheel was installed that has pickup rings for the center horn button. When the wheel was tightened down the steering wheel became very hard to turn. I found that the plastic pickup ring had come loose.
If it takes more effort to turn in one direction than in the other it's usually leaking seals in the steering gear spool valve. There was an instance where the problem turned out to be that a technician had removed the bolts that hold the steering column to the dash, and had not replaced them all. The steering wheel was at a slight angle, and the U-joint was binding in one direction. Make sure that the under dash U-joints are greased.
On the hydraulic side, normally low assist in one direction would indicate a problem in the spool valve of the steering gear. If you are sure it is not the gear, then check the output pressure of the pump. It should be around 1400-1500 psi.
Metal shavings in a power steering system almost ALWAYS come from deteriorating pump vanes. I always recommend using new factory pumps.
I have seen a few cases of a hydraulic hose deteriorating from the inside and little pieces of rubber hose would drop down every so often and block the steering fluid.
I have seen situations before where the pump output was adequate enough to give braking assist, but not enough to give proper assist to the steering. Proper diagnostic procedures whenever there is a low assist situation should always begin with a check of the source of the hydraulic power. While the gear may very well end up being the problem, this is where I would start given the questionable nature of the pumps.
With the cold weather setting in, I get some groaning with my PS system upon start-up. After it warms up it goes away. The fluid level is fine and looks like it's in good shape.
The groaning is usually from cavitation, and if it is really cold the fluid will be thicker and more prone to air bubbles. I live in Colorado, and I use cold climate power steering fluid to avoid this condition. You can buy it from any GM dealer, it is a field fix for exactly the condition you describe on late model full-size trucks.
One of my friends kept breaking the shafts on new power steering pumps. The problem turned out to be the hydro boost. The truck steered fine and was able to turn from lock to lock without any problems. This left the hydro boost. They used a Kent Moore tool to test the pressure and it read 300 psi when it should have read 75. My guess is that dirt plugged up the boost causing high pressure to build up. Combined with the pressure needed for the steering, the shaft broke.
Adjusting Your PS Box Free Play
Here is the procedure that GM Saginaw Division recommends to adjust the steering box.
Disconnect the pitman arm from the sector shaft, completely back off the sector shaft adjusting screw on the sector shaft cover.
Center steering on the "high point" then attach an inch lb torque wrench to the steering wheel shaft, the torque required to keep the shaft moving for one complete turn should be 1/2 - 2 in lbs. If the torque is not within these limits, loosen the thrust bearing locknut or tighten valve sleeve adjuster plug to bring the preload within limits.
Tighten the thrust bearing locknut and recheck preload. Slowly rotate the steering shaft several times, then center the steering on high point.
Now, turn the sector shaft adjusting screw until a steering shaft torque of 3 - 6 in lbs more is required to move the worm through the center point.
Tighten the sector shaft locknut to 35 ft lbs and recheck the sector mesh adjustment. Total steering gear preload should be 14 in lbs or less.
Install the pitman arm and replace back in vehicle.
NOTE: To try and adjust the sector shaft screw without doing the preceding will DAMAGE the steering gear. Most of the play is not in the sector shaft adjustment, it is the spool valve area.
My power steering seems to be leaking at the pump. It looks to be leaking thru the high pressure hose. I have replaced the original but still have the problem.. Not a huge leak but enough to drain it down and have to refill after a month or so.
When replacing a high pressure "BLUE" power steering hose assembly, I only use the AMG replacements and even then make sure it is positioned as far away from the exhaust manifold as possible. I've seen what the incorrect hose can do, and its not a pretty sight ...even if you succeed in getting the fire out quickly.
Replace Your Power Steering Pump
You want to make sure you have a split nut wrench. As I remember the high pressure hose is 19mm. I had two low pressure return lines going to the pump held by screw clamps (5/16 bolt heads), one from the hydro boost. and one from the cooler. The hydro boost. return has a 5/8 dual clip that hold it to the high pressure line which goes to the hydro boost., so they run together. From the hydro boost., a high pressure line then feeds the steering box.
I first disconnected the serpentine belt using a 1/2 inch breaker bar into the square hole in the idler pulley. Remember to note how the belt runs, i.e.: over or under the water pump. I then removed the belt tensioner so I could then remove the fan clutch and move the fan out of the way of the power steering pump. Removing the pulley is now pretty easy.
Some people remove the alternator (left the electrical connections but swung it out of the way and held it with a bungee cord) but it may not be necessary. To remove the bracket, I had one bolt under the truck, one in front of the engine hidden by a prominent rib in the front of the bracket (long socket with short ratchet, 9/16 or 15 mm ... can't remember), one stud to the exhaust and one bolt on the side. I had to loosen 2 bolts that held the pump to a second flat bracket that attaches to the back of the pump. This gives you enough movement to get the main bracket off the exhaust stud.
Once the bracket is off, the pump is held by 3 - 13mm bolts to the main bracket.
You need a steering pulley remover to remove the pulley. You also need a specialized installer to replace the pulley. This is a press fit and going on perfectly flat is a must. (a standard NAPA tool for under $30.00)
If you intend to replace the pump but use the original housing, watch out that you do not bend the case or you'll get a leak from the front of the pump. To remove the pump from the case, you remove 2 bolts with prominent shoulders and the 1 inch flange which connects to the high pressure hose. Using a rubber mallet and holding the pump shaft in a vise, tap off the housing and/ or gently pry with a small flat screwdriver. A spring and seat valve will come out of the flange connection hole. A rubber seal is internal to this flange hole. To reassemble, the hardest part is replacing the 1 inch flange connection. Replace the 2 shoulder bolts first but do not tighten. Then with your thumb, push the spring down and turn the flange connection to catch the threads. This is not easy for the spring is strong and the threads very sensitive to case alignment ... remember leave the two shoulder bolts loose.
Here's a little trick. Once you get the pulley more than 1/2 or 3/4 of the way pressed on with the installation tool you put the Serpentine belt on. The belt has enough friction to hold the pulley from rotating while you use a 1" open end wrench on the special press-on tool to push the pulley the rest of the way on.
Once assembled, you must prime the system.
Problems with the Power Steering Design
In my opinion there are two fundamental problems in H1 power steering design. First I want to say that the design is a standard one used in almost all cars and trucks.
First is the over pressure valve located inside pump. When the wheels are not turning freely in a situation where you may be jammed between the rocks the fluid circulates only inside pump and not through the cooler. This is difficult situation because there is no cooling at a time of maximum heat generation. You can boil power steering oil in this situation.
Second is flow regulator valve at steering box input. If sudden external force is applied to wheels this valve prevents free flow back over to the pressure valve. Pressure inside steering box can rise fatally. I have exploded one steering box hydraulically.
I have Milemarker Winch installed. With winch installation I also installed an industrial hydraulic filter in the loop and a debris collector magnet. I have also installed a permanent pressure gauge in the circuit. This is very useful with the winch. You can see pulling power from the pressure gauge.
BTW, the over-pressure valve operates about 100 bar = 1450 psi. When you start to hear a hissing noise when you are trying to turn the wheels this means fluid is flowing through the over-pressure valve (and heating very quickly). This doesn't require much steering wheel force. Brakes (hydro boost.) are another way to generate an over pressure condition. Light braking is usually between 20 and 40 bar but if you really step on the brake it is again 100 bar situation.
Another improvement is to replace the Dexron III transmission oil used in the power steering system with power steering oil or synthetic Dexron. John Ward at AMG suggested I use GM power steering oil because it won't foam as much as Dexron. This will prevent cavitation. I've also heard stories that Dexron turns into a waxy like solid under the right conditions and leaves this residue all over the place in the system.
Here's how it's done:
Use 6 quarts of PS fluid.
Drain - pull off bottom hose from cooler.
Pour PS fluid until it runs clear.
Start the engine and let any old fluid drain out while pouring new fluid in the Reservoir
If you have a hydraulic winch run it so the new oil gets into it.
Fill to capacity
Do the following if the system has been completely drained or you have replaced the pump or gear box.
The reason you MUST prime the pump BEFORE you start the engine is because it's dry. Initial moment of starting the truck will score the moving components in the PS pump.
You should jack up the front end and with the engine OFF, turn the steering wheel side to side while pressing on the brake repeatedly about 25 times to drive out the air from the high pressure side of the truck. After topping off the fluid, leaving the truck on jack stands you start the engine and at IDLE speed do the same thing again. Check the level of fluid. Finally, you take the truck off the jack stands, start it up and while stationary turn the steering wheel side to side GENTLY. If it feels good while turning and the pump is silent, you are done. If not, repeat ALL of the above.
I have replaced several pumps over the last 10 years. I replaced 3 this year because my Hydro boost. and my steering box was bad. This caused strain on the pump so I sheared off the shafts.
In line Filter
AMG performed power steering testing with an in-line filter a while back. For that test, they had to use a "transmission" in-line filter in lieu of a "power steering" in-line filter due to the Hummer's high flow (GPM) requirements at higher RPM's. The "SP/FILTRAN" filter did a great job of "cleaning up" the power steering system even on brand new HUMMER H1's!!! Don't recall the part number, but believe it is the in-line "transmission" filter FORD uses on its export vehicles.
Replace the Pump Cartridge
The pump cartridge used in the Hummer is the metric version of the pump used in GM trucks. Mine has "metric" cast into the pump body, right by the pulley shaft. They are available re-manufactured with a lifetime warranty from Parts America, number 7519606. The rebuilder is "Original Equipment Re-Manufacturer's".(NAPA NSP20860 $42.99 + $11.11 core) I'm sure there are other rebuilders also. The price is $50 exchange and a $10 core charge. If they need a cross reference, use a 2000 GMC Savana Van with the 6.5L diesel engine.
This cartridge definitely fits 92, 93 and 94 Hummers. I assume it fits all, but I have no way to verify that. If you are interested, you should look at the pump you have. On the back side, there are two studs sticking out. If this is the same pump, the stud nuts will be 18 mm. A 11/16" wrench will not fit, but just barely not fit. The outlet fitting that the outlet hose screws into will be 25mm. A 1" wrench will fit on with a little slop. Reservoirs (bodies) differ from year to year, but I don't think the pump cartridge does. It does not matter if you have an additional remote reservoir as in from 94 on. Replacing the pump cartridge in the reservoir is very easy. Remove the belt pulley with a small puller, remove the two studs on the back and the outlet fitting, push the cartridge out of the reservoir, replace the seals, (new seals come with the remanufactured pump) and put it back together in reverse order.
A Steering Problem That Nothing Would Fix
This truck came in with hard turning to the left which would lead you to believe that the steering gear was defective. The truck was in the dealer for a month and AMG had a field engineer come out to scope the problem.
Now, here is the verdict. Every component was changed, from hydraulic to mechanical, and the problem was still there. Never went away. Stumped everyone. From hoses to fluids, nothing was overlooked. When there was nothing left to change and the steering problem was still there, AMG said to take off my tires and put on new front tires and rims; problem solved. Why, no one seems to know. It makes no sense.
AMG replaced my four 16.5 rims with GSA's with all new 17" rims and MTR's.
The truck appears to be fixed, it certainly steers perfect and rides nice.
A Typical Story
I have had similar steering issues with my 1997 wagon ever since I bought it (new). AMG replaced the PS Pump and Steering Gearbox on more than one occasion. The truck was in the shop on several occasions to try and diagnose the problem. AMG sent down the experts to help. They never did resolve the problem. I have run MT's, GSA's, one-piece steel wheels, two-piece steel wheels, and alloy wheels. I even swapped the steering gearbox with the beefed-up AGR gearbox. The problem remained. Oddly enough, I installed the Cepek adjustable shocks (not due to steering issues) and much to my surprise, the difficult steering problem was solved (about 90% easier to steer when stopped or moving slowly).
IMHO, the Hummer power steering system is weak for the weight of the vehicle, the same Saginaw gearbox is used on many vehicles weighing less than half that of the Hummer. The pump doesn't appear to be a beefed-up version of the standard GM pump.
Power Steering Pump Blows Up
Power steering pump blows up while turning in my snowy flat driveway.
On a snowy day, I replaced the pump. I was able to turn the steering wheel maximum to right and left while on jack stands. Once on the ground I could turn left to the maximum with ease but right was very very stiff. Drove a couple of miles then parked it.
Put on jack stands. and once again made sure air was out of the system. Once on the ground, a right turn immediately snapped off the power steering pump shaft (2nd pump in 3 days). I thought replacement pump might have been a poor rebuild.
A peeved H1 owner during a non-rainy 45 degree MI day several weeks later, changed the power steering pump again, steering box, hydro boost. and all high pressure lines. Truck behaves better than new.
Turns out that the steering box sector shaft which has three teeth had one broken off and that loose tooth jammed the steering box leading to excessive pressure, hence blows the pump.
Dan, from Benchworks Steering Systems in Scottsdale informs me that my hydro boost. is shot and needs rebuilding. This also explains why 6 months ago I rolled down a steep hill when my engine stalled but put my foot to the firewall on the brake pedal. My nitrogen powered backup had no pressure thus no hydro boost.
Pump Blows Up 2
Upon tearing down the power steering pump, I discovered a very small, but definitely manufactured, piece of plastic lodged deep inside one of the Low Pressure inlet. It was so deep it could not be seen from the outside, but it lodged against the internal pump casing, blocking 90% of the fluid intake. This allowed pressure to build in the LP lines until burst pressure was reached.
Where did it come from? At the factory these pumps are all fitted with plastic caps which fit over the inlets to prevent debris from entering. The caps on the LP inlets actually have a small nipple protruding into the inlet tube. If your new pump has been in storage a long time, the caps get brittle. In my case, when the cap was removed, the nipple broke off inside the Low Pressure tube and ruined my day.
Why Steering Box Part Number Change in 1999
Can anyone advise whether the steering box is the same in all models 92-03. In approximately mid-1999 HUMMERs and HMMWV/HUMVEE's had a split in part numbers. The civilian HUMMER changed to steering gear part number 12460232 while the HMMWV/HUMVEE retained the old part number; 12339896. Part number 12460232 is currently the only replacement steering gear available for all '92 thru '03 civilian Hummers.
The later model gears use a different seal design for the sector shaft. It uses a single seal vs. the older gears using two seals. The casting has to be machined a little bit differently, so technically it is "different" part. Other than that, there is no practical difference between the two, and one is not really any better than the other.
I had fluid all over the reservoir no matter what the fluid level. It would actually get to the point where you could look down in there and hardly see any fluid, yet it would still get the reservoir wet after I wiped it clean and went for a drive. I took the reservoir out and inspected it. The bottom of it had what looked like a small crack, and the part where the cap locks in may have been slightly deformed. I chanced nothing. I replaced the reservoir, cap, and hose. The cap has a spring and rubber seal in it. Maybe the fluid just splashing around in there can overflow if the rubber seal is not tight. Either way, 40 bucks later (total) and no more leak. Fluid overflow from the reservoir (if not overfilled) is almost always due to air being present in the system. The source for the air may vary.
After a weekend of testing, I found two problems on my system. First off, I think that my improperly offset tires are putting extra strain on the steering components and my fluid is breaking down, or boiling as a result. When it happens it fills the reservoir with foam that overflows under the cap. I flushed and refilled with Dexron Synthetic fluid and don't seem to have the overflow problem, but the proper rims are definitely going back on. Secondly, I have a small crack in the outlet tube of the reservoir. I would have missed it without one of your shared insights. It is right where the tube meets the reservoir. I didn't see and had looked specifically for this twice before, but after a make-shift pressure test I saw it drip out.
Add the 4th Steering Gear Mounting Bolt?
Ever wonder what AMG's "reason" was for not using that 4th steering gear mounting location? Is it possible they know something about the HUMMER H1 we don't?
Hmmm .. possibly AMG's "reason" had something to do with an additional (4th) steering gear mounting point making the Left Frame Rail too rigid (reducing their design-in flexing in that critical transition area of the rail) thereby creating potential for cracks? IF .. indeed that was their "reason," then by utilizing that 4th steering gear mounting point the potential for cracks could be greatest around areas where the (rigid) steering gear reinforcement casting is welded to the (flexing) inner frame rail half.
As many of us have learned over the years, there are "always reasons for everything" on a HUMMER H1. Yes, they may not always prove out over time to be "THE BEST" reasons, but just the same, AMG decided to do this or that a certain way for a REASON ..not a WHIM !!!
Fix a Broken Steering Box Bolt Hole
The best prevention for breaking bolts and tearing up your frame is to make sure that your steering box bolts have not come loose. This happened to me at Durango. I had just completed a stressful climb and was driving over some nice flat rocks when I heard two popping sounds. It was 2 of my steering box bolts breaking. luckily the box and frame were fine.
This bracket is made from 1/4" thick steel. Grind off the paint and carefully weld around the crack. Grind smooth and weld the new plate to the frame. In my case I didn't have any cracks so I just bolted the plate to the frame. You may need to get longer steering box bolts.
Steering Went Out:
I had the steering go out on my truck. thank goodness it happened in a parking lot as I was going to hop on the freeway. The dealer said a valve went out in the steering box which caused the PS pump to go and the hydro boost. locked up the brakes.so now all have to be replaced.
I actually had a 99 open top in the shop for the exact same problem last week. And, yes, it did take replacement of all of those parts to fix it. What had happened was the needle bearings in the top of the gearbox (where the input shaft is) had come apart. They found their way out of the box and into the pump and into the hydro boost. Exact same symptoms: severe pulsating of the hydraulics, loose steering with and without power assist, brakes locked up (had to pull the pedal up with my foot to get it into the shop. Replaced gearbox, hydro boost., and pump, flushed cooler and lines, now all ok. Disassembled the pump, found 2 vanes seized in from debris going thru, a whole lot of rollers stuck to the magnet in the pump. The steering shaft on the box would actually move in and out while turning the wheels side to side; and no, the owner did not have an extended warranty. It cost about $2200. all factory parts.