intermittent power steering? 2019

So the power steering dropped out as if the vehicle had stalled.

This has just happened twice, two days ago, no hint before or since.

I was driving about 15 MPH and it just stopped working mid corner. Full fail, as if the motor had stalled, but no hint of a stall.


I was able to muscle through the corner, and then it came right back, as if it never left.

I didn't use the brakes during this short power loss, so I dot know if they were affected.

Happened again 20 minutes later, but after a key cycle for a ten minute pit stop.

Neither local dealer has heard of this issue.

Obviously it won't likely duplicate at this point, so I cant think of anything they could diagnose, but this is a huge safety concern. These trucks are all but un-driveable without assisted steering, and this causing an accident is easily envisioned.

I am running 35" tires, but I see no way this can be contributing, let alone the cause.

Anyone have thoughts?

Thanks.

Dave

 

Really need to know if the brakes were effected or not… so
when it happens again I would check the brakes.

Fluid full?

 

Dave, it may be a water pump bearing or a tensioner bearing about to fail. As you turn it applies torque to the belt and bearings. The belt loses tension, and you lose power steering. Shawn. Dave, I had this happen 30 years ago on an old truck. The water pump bearing went with no other issues and ended up in the neighbors front yard. The fan at that point was hitting the radiator. I forgot to mention the idler pulley in your case as well. If you are able to remove tension on the belt, you should be able to shake each of these to find the culprit. Or at least rule out some issues. Shawn

 

Thanks John, and Shawn. Shawn, this sounds super plausible; I appreciate the reply.

John, I guess I don't actually know how the brakes are powered, but presumably not via the power steering pump, correct?

Dave

 

The brakes are powered by the power steering pump.

So if you lose brakes too it’s points to the pump, but if you don’t lose brakes it points to the steering box.

If this was the case, which is plausible, you would also see voltage drop and should get a check gauges indication.

 

I don't have access now to look, but I want to say 19 was the first year of electric assist. Run your vin on the options page and see if it says electric assist steering.

 

Yes, 19 was the first year of adaptive steering.

Even if the electric assist fails there should still be hydraulic assist.

 

Not necessarily, "if you don’t lose brakes it points to the steering box". Still could be the power steering pump because there is a charged accumulator in the brake hydroboost unit ready to supply oil for brake boost if a brake application is needed. So, the brakes could feel normal even if the power steering pump failed momentarily.

I believe that when the engine is first started and the power steering begins to deliver oil, charging the hydroboost accumulator has priority - delivering oil to the steering gearbox is secondary. Since almost 100% of the time the accumulator is already in a charged state, this event will go unnoticed by the driver.

Unfortunately, it is probably going to be difficult to diagnose this particular symptom because it happens infrequently and there are several sources for the cause of this problem. To list a few:

* faulty flow control / relief valve in power steering pump
* faulty hydroboost operation
* faulty steering gearbox valving
* oil contamination affecting steering gearbox valving or power steering pump flow control / relief valve operation.
* inside liner of a hose collapsing
* and as mentioned - possible failure of a belt driven component (also, don't forget about possi le failure of the de-clutching alternator pulley that I believe is on the 6.7 Cummins).

@DFrank , if by chance your truck is still covered under some kind warranty, it might be worth a trip to the dealer. Definitely let them know of your concern for safety.

- John

 

I understand that the accumulator is for ABS use, and not normal braking.

That is why you need to cycle the ABS pump on a brake fluid flush.

 

Thanks team. I am still under (extended and power train) warrantee.

I figured dropping it off would
Be almost guaranteed waste of time, as the condition isn’t likely to duplicate on a rest drive.
If I had a good list of things to suggest they test, it might be worth it.

any further suggestions on what they should test?

 

From the 2002 FSM:

ACCUMULATOR LEAKDOWN
(1) Start the engine, apply the brakes and turn the
steering wheel from lock to lock. This will ensure the
accumulator is charged. Turn off the engine and let
the vehicle sit for one hour. After one hour there
should be at least two power assisted brake applica-
tion with the engine off. If the system does not retain
a charge the booster must be replaced.

As stated here, the accumulator is providing power brake assistance which is exactly what it would do in a situation where the power steering pump failed and the brakes were applied. I have performed this test many times and it is not even necessary to turn the steering wheel from lock to lock. With the accumulator completely drained, I can start the engine and the accumulator immediately charges without touching the steering wheel because the accumulator has flow priority. I can shut the engine off and one hour later pass the brake test using the procedure stated in the FSM.

To my knowledge this would be true because you would want to remove any entrained air in the brake fluid hydraulic system. But, this is not relevant to the accumulator operation in the hydroboost unit as it is a separate hydraulic system using the power steering fluid from the power steering pump.

If I am not understanding correctly what you are saying, please let me know.

- John

 

Nope you need to report that ASAP, that it goes into the recorder of the truck. Even if it isn't reproducible right now there is a chance that the warranty pay for it later on.