Power Steering Issues - update 5/20

[rv_safetyman]

Thanks guys.  Yes, Ed, you have seen me talking to myself.  Indeed, I sometimes answer myself .

Just so we are straight, my PS is always in the system.  The other port/circuit is EITHER the jacks or the fan.  I switch to one or the other via a quick connect.

Bob of the North called the other night and we went over some of the possible issues.  He came up with an interesting thought.  If the motor is switched to the high speed, there could be more restriction.  I will finish that wiring when I am in Iowa and do some playing.  I could easily switch to high speed when I am on tight roads at slower speeds.

Kent Widdison also called and we went over the complete system (I got it from him).  He had it on his bus and it ran fine.

My guess is that I have plumbed too big of lines to the fan and am losing flow in that circuit.

BTW, I have been chastised a time or two about telling folks not to go to a small steering wheel.  Well, if I had had a small steering wheel a couple of corners would have been interesting .  I won't chime in again on those threads, as you all know my opinion. 

Jim

[Len Silva]

I always talk to myself because I'm the only one who knows what the hell I'm talking about.

[Kenny]

Jim, Can you provide the complete part number of the pump you are using? Can you provide a schematic of the system including line sizes? Part number of the hydraulic fan motor?
Having a hydraulic background, my initial confusion is you mention it being a 2 stage pump. According to the manufacture this is a fixed displacement gear driven pump which will deliver X number of cubic / inches of hydraulic fluid per revolution regardless of pressure. The faster it spins, the more volume it delivers. The slower it spins, the less volume it delivers. Pump pressure is a product of downstream flow resistance. In other words if a pressure gauge was installed at the pump outlet and the pump outlet was piped directly back to tank, the only flow restriction would be the piping back to tank. Therefore the pressure gauge would indicate very low pressure to no pressure depending on the line size back to the tank. In this case the smaller the return piping, the higher the resistance thus higher pressure.
Now as in any hydraulic system using a fixed displacement pump, there must be a safety relief or regulator to limit the maximum system pressure or there will be a disaster.
Depending on the circuit design you have, my initial thought to your comment on hard power steering at slow speeds is, low engine rpm means low pump volume and the hydraulic fan being the path of least resistance is passing what little volume the pump is outputting which in turn will cause the pressure to drop.
My suggestion would be to add a restricting orifice to the inlet to the hydraulic fan motor. An orifice size could be calculated based on system components, piping sizes and lengths or you can simply experiment by installing an orifice to the inlet of the fan motor and installing a gauge visible from the drivers area but connected to the inlet of the PS box underneath you. As you drive with the fan running and making a turn, you will want to size the orifice so the gauge pressure does not fall below the PS box min pressure needed. The smaller the orifice the more pressure you will have to the PS box. Now there may be more to you system that meets the eye like volume and pressure requirements needed for the hydraulic fan motor but without a complete schematic and part numbers of the components in your system this is my only my initial thoughts.
Kenny

[rv_safetyman]

Kenny, thanks for offering to help.  I wrote to Haldex with part numbers that appeared on the pump and motor.  Here is their reply:

These are special W900 Series products we make for Daimler Trucks North America.  

Daimler P/N 61280126 is our model number W9A126L3G24C03AXS  - W900 Series pump
Daimler P/N 61280121 is our model number WM9A125R3R64VNBJS - W900 Series motor


They are a system (pump/motor) designed for a Thomas bus from what we can tell.

The PS plumbing is unchanged from before the hydraulic pump/motor change. I did route the return hose from the old reservoir to the new reservoir.  Per the BK thread, I am dumping the return into the top of the reservoir.  Kind of wonder if that adds air to the fluid somehow.

My fan circuit is very simple.  3/4 hose to a quick connect, 3/4 hose to the motor, and then 3/4 hose to the reservoir (with spin on filter in the line).  I just guessed at the hose side.  The ports are pretty large, so I figured that the motor need a lot of flow.  I ran a fairly straight 1 inch supply line from the tank to the pump.

Here is a photo of the pump:

Jim

[luvrbus]

Jim, isn't the power steering a open center hydraulic system and the fan a closed hydraulic system or the other way around not for sure 

good luck

[rv_safetyman]

Clifford, I am pretty sure that both are open center systems (fluid flows at all times through both circuit).

In the case of the fan, the fluid is always doing work.  In the case of the PS, I think the fluid flows to the return until the PS calls for assist.


Jim

[rv_safetyman]

OK guys, we left on our trip today.  I felt as nervous as a whore in church!!  First is the whole engine/transmission situation given my track record.  The next was the issues with the new hydraulic system.

Bottom line, all went well.  My blood pressure dropped to its normal boarder-line level after about an hour.  The engine and transmission ran very well.

I was really nervous about the power steering.  However, there was not problem one.   I even went a round about way to get to the highway so that I did not have to drive on our tight twisty canyon road.  Turned out that I did not need to take that route.

I did change the spin on filter for the PS circuit.  Can't believe that would make that big of a difference.

I shot the temperature of the reservoir and it was always in the 120-130* range.  And it is not full.  The charge air cooler fan did a good job as well.  I can tell that I will need to wire up the high speed for the really big hills, but I won't see those till I get back home.

We have about 350 miles to go tomorrow, so we will see if we have a repeat of today's good results.

Maybe it is about time that something goes right

I do plan to put dip tubes in the return lines so that fluid is returned into the fluid.

To show you how well things went today, we found a truck stop that had $2.96 diesel (no charge for CC)  *AND* red diesel for my auxiliary tank (for Aqua-Hot and generator) at $.44 off the normal diesel.  I needed 30 gallons so that worked out well.  Our local station has a price differential of 20 cents - what a ripoff!!!

Fun reporting a good day for a change!!!!

Jim

[robertglines1]

have been following along and learning...you deserve to have the problems worked out....more fun to drive and enjoy than to worry and work on.....

[Brian Diehl]

Jim, I'm so glad you were able to actually get down the road and have no engine/transmission problems!  Way to go!


I don't think I saw where you mentioned exactly what it was that caused your original transmission ECU to fail.  What was the root cause analysis on that?

[rv_safetyman]

By Brian Diehl:  Jim, I'm so glad you were able to actually get down the road and have no engine/transmission problems!  Way to go!


I don't think I saw where you mentioned exactly what it was that caused your original transmission ECU to fail.  What was the root cause analysis on that?

Brian, I am not exactly sure how the ECU got screwed up.  As I approached Raton Pass on the way home from Albuquerque, I made a quick decision to pull over and turn on the misters (charge air cooler issues).  For some reason, I kicked the transmission into neutral (a normal process for me at very slow speeds).  When I kicked it into neutral, the transmission seem to react strangely.  When I went to take off, the transmission did not want to shift.  I tried it a couple of more times and after about 4 times, it shifted and we went on down the road.  About 100 miles later, the transmission would not shift out of 10th.  I nursed it to a rest stop and did a bunch of trouble shooting with my Pro-Link.  The results were that the ECU had "failed".  That is when I put the replacement ECU on and ran into the gear ratio incompatibility and got to go home behind the hook.

I am not sure if the ECU has gone belly up or if there is a software issue.  I have taken it along with the wrong gear ratio ECU to the Eaton rep to have them reprogrammed.  My hopes are that the original ECU is not toast.

I still have a hard time understanding how my kicking the transmission out of gear would cause the ECU to "fail"

I will also post this on the thread about the AutoShift problems to keep everything together.

BTW, we just traveled 700 miles and did not have any problems - what is wrong with this picture Grin

Jim