Overactive steering pump?

[bleucrew6.2]

Lately I've been experiencing a weird/scary situation with the steering assembly in my truck. As I drive down the road, it seems like it will just veer a bit, and when I compensate for the veer, it oversteers in the opposite direction. Road surface doesn't seem to have any bearing on this happening. Tie rods, ball joints, and pitman arm ends don't have any play in them. I checked the wheel bearings, and found a little play which I corrected. Tire pressure is correct also. I had a friend check for bubbles in the power steering pump as I slowly turned the steering wheel, and could swear I saw the drivers side wheel kind of jump or lurch a little bit in the direction I was turning it. This looked like what I feel in the steering as I'm driving. The only time this has never happened is when I am driving at highway speeds. It seems like it tends to happen at speeds between 20 and 40 mph, and especially after I have come to a stop at an intersection and turned right onto the intersecting street.
I'm stumped. Anyone have any ideas?

John

[Subzilla]

Check for cracks in the frame at the steering pump. Because this is a common thing, there are bolt-on and weld-on kits just to resolve this issue.

http://www.offroaddesign.com/catalog/steeringkit.htm

I've been trying to fix a funky steering problem, similar to your symptoms, on my Blazer for the last 3 years. I basically rebuilt or replaced everything on the front end and I still have a weird steering wandering problem. I finally gave up and accepted it. My Suburban with the 4" lift and 35" tires actually drives and steers better than my stock Blazer!

Anyway, keep checking! It just might be the steering pump, I don't know.

[HH]

Also check the U-joints in the front axle half shafts.

[Subzilla]

HH, how would these u-joints affect the steering? Mine don't even turn until I manually lock in the hub.

Thanks.

[bleucrew6.2]

HH, I'm also curious about the effect the u-joints could be having on my steering if the hubs are unlocked. Can you explain further?
Wooee...the ride to work this morning was really scary. I almost ended up in the ditch a few times. I need more info about the steering box and steering pump relationship. Is there a direct connection between the steering column shaft and the pitman arm, or is it some sort of fluid\friction connection. My steering definitely felt disconnected from the input of the steering wheel this morning.

John

[HH]

If the u-joints are worn (rusty internally) and binding they can cause a pull to one side or another. Although the axles are not locked in they still have to turn left and right. I mentioned this because you stated it appeared to happen after you made a turn.

[Subzilla]

John,
Something else to check - the rag joint on the steering column there in the engine bay. My Suburban was very loose and worn and causing some "wander". With the steering wheel unlocked, grab the column with Visegrips and wiggle it (carefull there). Look for play. I found a good used at a steering gear rebuilding shop.

[bleucrew6.2]

Thanks for the suggestions! The thing is, I can cause this problem to happen with the truck parked. Standing outside the drivers door and SLOWLY turning the steering wheel from lock to lock. At some point past center, in either direction, the front wheel seems to jump/pop/lurch a little bit in the direction of the turn. I can feel this happen as I drive. At one point this morning, after turning onto a side street, I had to compensate for this problem by holding the steering wheel a quarter turn past center. Then, of course, the steering system "corrected" it's position- leaving me heading for the ditch. When I tried to straighten out the beast, I ended up swerving the opposite way- across the center line of the road. I am going to drive very carefully home and park it until this gets sorted out. It is just to dangerous to drive it like this.
Can this maybe be caused by some fluid pressure fluctuation from the steering pump? Fluid in the pump looks dirty, but doesn't smell burnt. Pump runs quietly with no moans or groans.

John

[DmaxMaverick]

A few possibilities come to mind....

Variable assist steering, if your truck has this.

Steering pressure regulator in the hydroboost unit. Controls hydraulic flow to the steering gearbox. Your problem isn't likely the pump, as you would have similar issues with the brakes (you don't, do you?).

Upper/lower control arm bushings and knuckles. I had a similar issue with a '92 model. The upper control arm bushing disintegrated, causing really bad steering pull and wandering. It would also "clunk" in turns.

[JohnC]

Check for a frozen ball joint, tie rod end, etc. while you're in there...

[bleucrew6.2]

I spoke with a truck mechanic yesterday. I work for a school, and he does the work on our busses and trucks. I hate bothering him... he doesn't make money answering questions on the phone.
He also suggested checking the u joints. His other suggestion was that I have a sticky valve in the steering box that isn't controlling the fluid pressure the way it should. His description of the symptoms associated with this valve problem seem to totally match my situation.

I'll keep y'all updated.

John

[Subzilla]

Yikes! Don't drive that thing! That sounds scary. Please let us know what you find.

[More Power]

HH, I'm also curious about the effect the u-joints could be having on my steering if the hubs are unlocked. Can you explain further?
Wooee...the ride to work this morning was really scary. I almost ended up in the ditch a few times. I need more info about the steering box and steering pump relationship. Is there a direct connection between the steering column shaft and the pitman arm, or is it some sort of fluid\friction connection. My steering definitely felt disconnected from the input of the steering wheel this morning.

John

With or without hydraulic power assist, the linkage between the steering wheel and the tie rods on each spindle is a direct one. The steering wheel would have to also jump if there's no defect in the mechanical connection between the driver and the front tires. Your description sounds like some component in the system is bad, be that a steering shaft, steering gear, tie rods, drag link, etc.

Jim

[97-6.5TD-F]

I am pretty sure he has an old body style crewcab truck.

I would look at your steering linkage while you get someone to vigorously move the steering wheel back and forth and watch for any loose parts. I agree it could be a cracked frame around the steering box, but it could be anything.

Inspect the front leaf springs carefully, also. The bushings tend to hammer out and move around.

[bleucrew6.2]

Thanks for all your suggestions! I have checked tie rods and pitman arm rod ends. No noticeable play at all. Can't find any cracking around steering box area- the box is now out of the truck, so inspection is easy. U-joints and locking mechanisms on both sides have checked out. I supported the truck with both front wheels off the ground, and used a jack under the steering knuckles to check for vertical play, as well as a long bar to check for vertical and side play. All seems well in these areas.

The one symptom related to a bad steering box the truck mechanic mentioned that really hit home with me was that "sometimes the truck will just steer itself"....mmm hmmm... now that really sounds like my situation I think. He claimed that the valve could stick until the fluid pressure built up behind it and opened it causing an overeaction in the motion of the box. He also asked if the truck had developed any problems with the steering gear returning to center- yes it has, and as near as I can tell, about the same time as the swerve thing. He is a Chevy diesel pickup guy, and claimed that this is not that uncommon a problem.

I'll be picking up a rebuilt steering boc today at NAPA, as well as a pump(what the heck, right?), and will be waiting for a break in the Baltimore weather to install it. Wife is coming around to the idea of a garage in the near future.

John

[bleucrew6.2]

Jim, I do feel this through the steering wheel. It feels like one or both the front wheels just jumped into a turn- further than I wished, of course! Joshua, yes it is the older body style. Sometimes its a bit of trouble getting the correct parts for it. It seems to better fit the description of a 1987 one ton 4x4 crew cab... or suburban. Apparently, these trucks weren't updated until 1991(?).

John

[Subzilla]

You know John, you got me thinking that maybe my steering pump might be my culprit. As I earlier stated, I replaced or rebuilt everything including spring bushings, stabilizer bushings, tie rod ends, drag link ends, ball joints, adjusted bearings, ... but I don't think I replaced the steering box. I need to dig through my reciepts and check as this was 3 years ago or so. I'll add it to the list of chores. Let us know if that fixes your situation.

[DmaxMaverick]

If it were the pump, the brakes would be equally "quirky".

[bleucrew6.2]

Regarding the brakes on this truck.. No real problems there. Slightly warped passenger side rotor (not yet a serious issue), but no variation in braking power or pedal feel. I'm only replacing my steering pump because of the age/mileage on the truck- about 110,000 at this point, and because I didn't like the color of the fluid much. Considering the low cost of the part, and that the only mechanic I'm paying is me (?!), I figured I would just eliminate future work on this system as much as I can. All hoses look really good, or I'd replace them too.

John

[DmaxMaverick]

PS pumps can be funny animals. The OEM on your truck, even with the miles, may be better than any reman you get. They work, til they don't. I thought, like you, on my '85 pump. Way back when, I bought a new GM pump and stored it. It's still stored, in the box. The OEM with over 1/2 million miles is still going strong. No abnormal noise, no leaks. At the same time, there are some that don't go 50K, and some that have to be replaced regularly at less. If belt and pulley health is always good, and the fluid is changed regularly, it should last a long time. I installed a cooler in the return on mine, so heat is less an issue. And, I've always used Dexron III in it, synthetic from about 200K on.