Steering Freeze Up

[bobedson]

I suspect you are using reman parts. For the PS pumps either get NEW or pull one from a wreck in a junkyard. The junkyard one was likely working at impact. Reman is something that was ruined and maybe repaired properly or not. If not the debris from a possible pump burn up will dust the entire system. Last reman pump I will ever use was a snow globe in the oil and the shaft quit touching the seal. So in 30 min it had dusted the system and started leaking from grinding new clearances. I had to replace the HB, PS pump, steering box, hoses, flush the cooler, and added a in line filter.

Off the cuff fluid flow goes from pump to the HB unit: then to the steering gearbox. This means the brakes get dibs on pressure and can take it all leaving nothing for steering.

IF the brakes worked you could look at the steering box, but, they don't. Pump or HB...

So something like a kinked return hose off the hydro booster keeping the brakes applied is possible. So is a leaking accumulator in the HB. Are the brakes soft or firm to apply before engine start after sitting overnight?

If the accumulator is leaking down it's going to want to be charged up as soon as the engine starts. A weak pump may not be able to generate enough pressure and they sit fighting each other. Pump can't get any flow and accumulator has the flow blocked waiting on pressure.

The internal pressure relief valve on the pump may be wrong: for a gasser with PS only and set too low. Rebuild outfits don't take the time to care about special diesel settings in the PS pump for the HB. So the pump may be bypassing through a weak gasser relief valve until the HB accumulator can charge up and release the pressure to the rest of the system.

What oil you running in the system? Had a GM that had a TSB to use a revised synthetic fluid due to stiff steering.

Some outfits can put a pressure gauge on the pump. IMO start with verifying proper oil then replace the PS relief valve to make sure it's the proper diesel pressure part. If it's a reman pump odds are good it's just a junker with a poor paint job: replace it with better.

All good stuff, and pretty much have tried it all, hence the frustration. The problem was there before, for many years with the OEM pump. Pump failed a year ago, replaced with not one but two remans so that is why I stopped suspecting the pump since it had the same issue. Cold weather got me tracking it down again so replaced the hydroboost, master cylinder and of course flushed the system again for the 5th time. Same problem, when freezing temperatures occur both steering and brakes freeze up on start up, brakes are not applied, truck will move, just hard pedal and don't work. I guessed the same thing, pressure spring, accumulator, etc. so HB should have solved those issues. Fluid is Amsoil synthetic, changed from the OEM oil, no help there. Actually during the HB change found the return line fitting a little loose, thought maybe it was sucking air and creating a bubble lock on start up but after replacing the HB, bleeding, new fluid, again no help. Hard to suspect the steering box since the problem affects the brakes as well but not much else to turn to at this point.

 

[Tuesdak]

Pump is submerged in the tank so it can't airlock. (Unless the fluid was foaming at shutdown.)

It is possible something is blocking flow in the steering box, but, IMO you should have brakes. (Fiction has to be plausible the truth does not.) Again even in warm weather an accumulator test is possible: 2-3 pumps of the brakes before pedal gets hard engine off.

Not clear on this exact drive setup, but, isn't the vac pump driven off the same assembly? Do you have vacuum when this happens? Aka is something slipping till it warms up (aka no pump RPM)?

 

[bobedson]

Pump is submerged in the tank so it can't airlock. (Unless the fluid was foaming at shutdown.)

It is possible something is blocking flow in the steering box, but, IMO you should have brakes. (Fiction has to be plausible the truth does not.) Again even in warm weather an accumulator test is possible: 2-3 pumps of the brakes before pedal gets hard engine off.

Not clear on this exact drive setup, but, isn't the vac pump driven off the same assembly? Do you have vacuum when this happens? Aka is something slipping till it warms up (aka no pump RPM)?

Yeah, I get no brake pumps at all before the pedal gets hard. New accumulator with Hydroboost so don't suspect that. Yes the PS pump and Vac pump are driven from the same assembly. Have vacuum because the heater controls work, not much else runs on vacuum. Thought about linkage freezing up but pretty much trashed that idea since I have no brakes in addition to the steering locked up. I am not sure but I think the pump assembly is gear driven from the accessory case so no belts to slip. I wish stuff would just quit working, much easier to fix. This entire system works fine until the outside air temp falls below freezing and the truck has to sit out in it more than 3 or 4 hours. Soon as I crank it up and let it warm a bit I can forcefully turn the wheel enough to turn the truck but it takes all the strength I have then suddenly it breaks loose and all is normal again. Seems like when something breaks loose warm fluid is then getting through and everything fine. Even suspected there was water getting in somewhere and freezing but several flushes revealed no contaminated fluid.

 

[Tuesdak]

Yeah, I get no brake pumps at all before the pedal gets hard. New accumulator with Hydroboost so don't suspect that. Yes the PS pump and Vac pump are driven from the same assembly. Have vacuum because the heater controls work, not much else runs on vacuum. Thought about linkage freezing up but pretty much trashed that idea since I have no brakes in addition to the steering locked up. I am not sure but I think the pump assembly is gear driven from the accessory case so no belts to slip. I wish stuff would just quit working, much easier to fix. This entire system works fine until the outside air temp falls below freezing and the truck has to sit out in it more than 3 or 4 hours. Soon as I crank it up and let it warm a bit I can forcefully turn the wheel enough to turn the truck but it takes all the strength I have then suddenly it breaks loose and all is normal again. Seems like when something breaks loose warm fluid is then getting through and everything fine. Even suspected there was water getting in somewhere and freezing but several flushes revealed no contaminated fluid.

"I get no brake pumps at all before the pedal gets hard"

The accumulator has leaked down at this point. New parts do NOT mean "good parts" or it ate some debris. Do you get any reserve "soft pedal" after engine shut off? How about 5 min later?

So the "discharged" accumulator is attempting to charge up and is asking for 100% of the fluid flow/pressure at this point. So the pump may not be able to provide enough pressure to "charge" the accumulator, the relief valve has popped open due to a wrong or weak spring or other blockage. the accumulator itself may be jamming and unable to release the line pressure/flow. The hose to the HB unit and it's return hose should be replaced outright. Weird, but, ANY restriction on the HB return line can keep the HB stuck "on" taking all the pressure/flow. This includes an in-line filter: filters go on the return line from the steering box ONLY.

Does the PS pump make noise like it's at full steering lock during the condition? This would indicate the relief is open and pump is at full pressure.

Some HD vehicles have a PS fluid cooler: is there any damage to the one (if equipped) on yours?

 

[bobedson]

"I get no brake pumps at all before the pedal gets hard"

The accumulator has leaked down at this point. New parts do NOT mean "good parts" or it ate some debris. Do you get any reserve "soft pedal" after engine shut off? How about 5 min later?

So the "discharged" accumulator is attempting to charge up and is asking for 100% of the fluid flow/pressure at this point. So the pump may not be able to provide enough pressure to "charge" the accumulator, the relief valve has popped open due to a wrong or weak spring or other blockage. the accumulator itself may be jamming and unable to release the line pressure/flow. The hose to the HB unit and it's return hose should be replaced outright. Weird, but, ANY restriction on the HB return line can keep the HB stuck "on" taking all the pressure/flow. This includes an in-line filter: filters go on the return line from the steering box ONLY.

Does the PS pump make noise like it's at full steering lock during the condition? This would indicate the relief is open and pump is at full pressure.

Some HD vehicles have a PS fluid cooler: is there any damage to the one (if equipped) on yours?

Well, some good ideas here I haven't tried yet. I always get good soft pedal after shutoff, have not tried 5 minutes later. But of course the problem is freezing in cold temps so even an hour after shutdown it is still a warm engine compartment and start up again is normal. I don't remember the PS having a cooler but will look again for sure.
I am going to change out all the lines next and see if any difference. The current lines are OEM from 1998 and the problem has been there since new. Will also try to install a filter in the PS return line although with the multiple flushes and new pumps I don't suspect debris blocking the lines. I did clean the small screen on the pump but found no debris in that screen.
Of course anything I do can't be tested until the next cold weather which we now probably won't see until next winter.