[jdkskyking]

                                           

[johnkosir]

Every Newell is different
712 built Nov 2004 DD 60 series ZF steering
gold hydraulic junction block 
For sure no low fan, high fan when solenoid denergizes @ around 210 on silverleaf, off at 195, allways towing 20,000 lbs stacker, never have had problems overheating,  but I limit throttle to 15 gallons a minute on hills and manually down swift so the transmission won't hunt
I lost my power steering in Ocala on the way home 2 years ago and Richard came up and helped me patch it up to get it home, we both though that I probably damaged something when the solenoid valve for high fan come loose and I lost my hydraulic oil, lost power steering about 600 miles later, when steering started to fail, I pulled over at the next rest area and checked hydraulic oil it was ok, I don't think any had leaked out, was 9:00 at night and I did not feel like dealing with it then, when I got up it the morning there was  3 gallons of hydraulic oil on the ground.
We were able to patch it up so I could drive it home with no power steering, it was a challenge, but doable a lot of effort for gentle curves on the interstate, and very very difficult to get in and out of rest areas and truck stops. I never had any power steering it did not matter if motor was hot or cold fan motor on or off. 
Because of Jeffs post on accumulators I checked my accumulator pressure, it was 40 psi, it still was turning the back wheels properly when I backed up, because accumulator is hazmat no one would ship it across the border, so I charged up my 20 year old accumulator up with nitrogen and had a new one shipped to Florida, it is still holding pressure I checked a week ago I am a refrigeration mechanic so I always have nitrogen and the pump to add oil with me so changing it will not be a problem. 
712 has a piston motor with a brass wobble plate for the fan motor, After many calls to Newell and Hydraquip, I was able to figure out that it was the fan motor by capping the 2 lines to the fan motor, Newell told me to put gauge in series with the hydraulic line to the steering box to check for pressure, (did not have to do this because 712 had a gauge in the distribution block, the gauges would eventually leak so Newell stopped putting them in)  nobody told me there would only be 500 psi pressure until you turn the steering wheel it took me many tries to figure this out, when you think about it, it makes sense. Probably like a pressure washer and the block unloading if nothing is calling for pressure with the fan being priority if there is not enough volume. This is just a guess if I am wrong can someone please correct me. I finally tried the steering wheel with the lines capped and found that I had power steering, so I took the fan motor and overhung load adapter apart, the front seal for the load adapter had distorted so much that it blew the spring out of it and the lip was no longer touching the shaft that it was supposed to seal against, the back seal was damaged, the seal between the motor and the load adapter was hard as a rock. The wobble plate had small gouge in it, was only 0.003" deep (months later I bought a surface plate for something else and was able to measure it, it had some deep groves that were part of the design that I thought were damage, It was $500 if I had of known I would of ground 0.003" off it on my surface grinder and got it lapped) but I think it was enough for the motor to bypass so much oil that the return line could not handle it and distorted the front seal causing it to leak, and put the block into fan priority, and loosing power steering.
 Replaced the wobble plate, had the end of the piston that rides against the wobble plate lapped, changed the seals, put it all together and it is still working

[jdkskyking]

Is yours a ZF suspension?

[johnkosir]

Yes ZF steering and suspension

[orbit1957]

It’s been a few years since I marched down the gold hydraulic block path but I’ll try to recall what I know. I have a spare block… part of the di$covery phase of my journey… 

My coach is a little different with a Cat-13 engine and VICKERS 20 hydraulic pump but I’m betting the manifold is the same. I’ll speak to mine

You’ve been introduced to the spool valve and the orifice used to determine fan RPM in either low or high speed. It’s been a while since I tried to chase down manifold info. 

The manifold was designed by HydraQuip in Tulsa OK. The designer has moved on. 

In addition to the spool valve system there are two pressure relief valves, RV5 and RV6. The RV5 valve is the overall system pressure regulator while the RV6 valve protects the ZF Steering Gear box.
The ZF Gearbox also has its own internal pressure relief system, the RV6 is an extra measure of protection. 
On mine… if I recall, RV5 should be set somewhere around 2250 psi and the RV6 is set at a lower pressure, 1800 psi ish. On the forward side of the block you should find the values stamped in the block. Your pressures may be different, I’m assuming a DD60 and a different hydraulic pump.

On mine, LOW SPEED FAN is equivalent to 1/2 the engine RPM. If the Engine ECM calls for HIGH SPEED FAN the ratio is 1 to 1.

If I recall, my orifice disc was stainless steel. 

Eliminating the orifice disc could change behavior of the fan RPM system. 

I do know that the system was designed to share hydraulics and in LOW priority goes to the ZF Steering Gearbox. In HIGH…. The fan is the priority and the gearbox gets what is left over. 

BTW
The ZF RAS System hydraulics is a separate closed loop system that incorporates a hydraulic pressure accumulator to function properly. 

The forward “MASTER CYLINDER” utilizes gearbox hydraulic pressure for assistance moving the internal components of the cylinder but is not directly involved in moving the TAG tires. I’ve posted extensive information about the ZF RAS system. 

The ZF RAS Pressure Accumulator has a 10 year life span. If you have an original it should be replaced or the TAG steering system will not funny properly and can become inoperative to the point you will not be able to back up your coach in certain circumstances. The TAGS will caster forward but not backwards like the front wheels of a shopping cart. 

I’m here to help if you need anything. 
JK

Hi Jeff, Great info to help understand our hydraulics better.  I'm lacking any low speed fan operation.  I thought I read that at some point it was suppose to be that way. If you or anyone else have any information on the low/high speed configuration please pass it on. Thanks for sharing.  Kevin

[jdkskyking]

If I recall…. 

When the engine coolant temperature is in the normal range, the engine ECM provides a 12v DC current to a relay in the engine bay electrical box, mine is accessed from the right side engine bay door. 
The relay then provides 12v current to the spool valve solenoid and in turn the system runs on low. On my 2005 version, during normal/low speed operation the fan rpm is 1/2 the Cat-13 engine rpm. I used an optical rpm gauge to determine my fan speed. 

Note: During our discovery phase, Joplin Missouri Caterpillar found that my C-13 ECM was NEVER programmed to provide the 12v DC current to the relay. 
Newell jumped the solenoid relay and guess what…. My fan ran on low speed. In other words mine too always ran on high…. And I also know why… hint, fan blade pitch set to the minimum pitch because the VICKERS V20 hydraulic pump can’t handle anymore pitch… not enough fan pitch = not enough air to cool the system…anywho… Cat programmed the ECM and at a coolant temp of 217° the 12v is removed to the solenoid system and the fan goes to high. On my rig 217° is way past the point of no return so I installed a temp sensor in the coolant system that catches it at 212°… I also re-pitched the fan blades to 25° but there are consequences to doing that that you should be aware of should you choose to do the same.

Back on topic. 

On mine, high fan speed equals the engine rpm. 

The first thing I would check is if you have power to the solenoid. 
If I recall, Newell replaced my Solenoid during the early days of troubleshooting. 

If the solenoid isn’t functioning the system will always run on high, the failsafe mode in the event of a failure in the solenoid system… 

If there is no power, then more investigation must occur.

So you know… in my 2005 version “Gold Block”. In the normal mode the steering circuit is prioritized. Thats a good thing right? I have video of the cooling fan stalling as I make turns. 

In “HIGH MODE” all of the hydraulic fluid/pressure/flow is redirected to the cooling fan motor and the Steering Gearbox gets what is left over…. 

Two additional items to know, the gold block has two pressure relive valves, a RV5 that protects the entire hydraulic system by sending fluid back to tank, and a RV6 valve that protects the ZF steering gearbox. The pressure values are stamped on the block body. 

SIDE NOTE: The ZF Steering Gearbox has built in internal pressure relief valves so the RV6 is an extra measure of protection. 

Start with 12v power and go from there. 
JK

[johnkosir]

712 Nov 2004 ZF suspension and steering,DD 60,  gold distribution block. No low fan, fan comes on when there is no power to the spool valve in the distribution block turns on @ 210 off at 195 on Silverleaf

[orbit1957]

It’s been a few years since I marched down the gold hydraulic block path but I’ll try to recall what I know. I have a spare block… part of the di$covery phase of my journey… 

My coach is a little different with a Cat-13 engine and VICKERS 20 hydraulic pump but I’m betting the manifold is the same. I’ll speak to mine

You’ve been introduced to the spool valve and the orifice used to determine fan RPM in either



low or high speed. It’s been a while since I tried to chase down manifold info. 

The manifold was designed by HydraQuip in Tulsa OK. The designer has moved on. 

In addition to the spool valve system there are two pressure relief valves, RV5 and RV6. The RV5 valve is the overall system pressure regulator while the RV6 valve protects the ZF Steering Gear box.
The ZF Gearbox also has its own internal pressure relief system, the RV6 is an extra measure of protection. 
On mine… if I recall, RV5 should be set somewhere around 2250 psi and the RV6 is set at a lower pressure, 1800 psi ish. On the forward side of the block you should find the values stamped in the block. Your pressures may be different, I’m assuming a DD60 and a different hydraulic pump.

On mine, LOW SPEED FAN is equivalent to 1/2 the engine RPM. If the Engine ECM calls for HIGH SPEED FAN the ratio is 1 to 1.

If I recall, my orifice disc was stainless steel. 

Eliminating the orifice disc could change behavior of the fan RPM system. 

I do know that the system was designed to share hydraulics and in LOW priority goes to the ZF Steering Gearbox. In HIGH…. The fan is the priority and the gearbox gets what is left over. 

BTW
The ZF RAS System hydraulics is a separate closed loop system that incorporates a hydraulic pressure accumulator to function properly. 

The forward “MASTER CYLINDER” utilizes gearbox hydraulic pressure for assistance moving the internal components of the cylinder but is not directly involved in moving the TAG tires. I’ve posted extensive information about the ZF RAS system. 

The ZF RAS Pressure Accumulator has a 10 year life span. If you have an original it should be replaced or the TAG steering system will not funny properly and can become inoperative to the point you will not be able to back up your coach in certain circumstances. The TAGS will caster forward but not backwards like the front wheels of a shopping cart. 

I’m here to help if you need anything. 
JK

Thanks JK, The fan on mine has high only mode and good voltage to the solonoid for it's operation.

[orbit1957]

I am dogpiling on this post, just in case an owner with steering problems stumbles upon this thread using a search engine.

Let add a couple of key points that are covered in other posts on similar topics.

One, if you have the gold anodized aluminum block that controls the hydraulic pressure to the fan and steering gear box, you must understand that the priority is to the fan when the high fan circuit is activated by the engine computer. That prioritization can have unintended impact on the steering gear box IF there is a problem with the hydraulic fan motor.

So what you say? IF the internal seals are blown in the fan motor, it will negatively impact the steering. There is no outward or visible sign that the seals are blown. Here is how it will manifest. The coach will have steering until the engine reaches operating temperature, and then the steering will suddenly degrade when the engine computer activates the fan. When the internal seals are blown, the hydraulic pressure flows around the gears in the pump without restriction, and flows out the return line. None goes to the steering gear box when this happens. One owner replaced steering gear box and hydraulic pump before finding the root cause.

There is a derivative of this fail mode. The fan motor can fail at the front seal. In that case, you will know you have a leak because of the mess in the engine bay. It is hard to tell if the leak is the fan motor or the overhung load adaptor. Again the symptom is noticeable loss in power steering.

For those of you with steerable tags, either of the above situations will make the coach EXTREMELY hard to drive. Part of the steerable tag system has an independent hydraulic system to recenter the tag wheels. It takes the power of power steering to overcome the self centering feature. The coach will be almost impossible to turn the wheel at slow speeds.

Again, all the above info is contained in other threads that posted over the past ten years. My summarization was an effort to help someone in the future, and not to steal other’s post or pose as the subject expert.

Good additional information Richard.  Thanks for chiming in! Kevin

[orbit1957]

712 204 ZF suspension and steering, gold distribution block. No low fan, fan comes on when there is no power to the spool valve in the distribution block turns on @ 210 off at 195 on Silverleaf

Thanks John for the info. I wish there was a low speed.  My FOCS (Fan Overide Cockpit Switch) is a nice control function. Always like playng with switches, the kid in me always wants to see what this one does!  Kevin