Hydraulic fan speed controll

[ranger magnum]

Hey all...

This may be a bit of a long winded post, done on my phone. Apologies in advance for anything autocorrect says...

1993 Fleetwood pace arrow 38? pusher. Cummins C8.3 backed by an Allison MD3060

Problem:

Getting intermittent coooant overtemp warnings. Idiot light on dash comes on at 220*F. Dash gauge is not graduated. Only numerical indicators are 160 and 250*F. Light comes on. Temp rises to an estimated 225-230. Stays there 60 seconds, then falls to an estimated 185. This cycle repeats itself over and over.

Diagnosis:

Driving through the Nevada desert in August, I opened all engine compartments to extract any hot air. Driver window was down, when all of a sudden I heard the telltale sound of a fun clutch engaging. Within moments, temps fell. Once temp fell to estimated 185, fan clutch kicked off. Temps rose, clutch kicked in, same thing.

The issue is that the fan clutch isn?t kicking on when it should, and instead allows the engine to rise to a dangerous level. This fan needs to be more consistent.

However, there is t a fan clutch that I can see. It is a hydraulic system with a direct drive. Thus, there needs to be a priority valve that sends more fluid when engine temps require. But I cannot find any such valve or any means by which the fan is sent the info it needs to spin faster.

Fleetwoood has been no help. I mean maybe they could be, but they never answer the tech line, and instead you are put in a que of callers. I?ve waited over 30 minutes,  it to no avail. Oshkosh has no info, and tells me it is a coach issue, and Cummins says the same.

Anyone have any insight? I?m about to start taking the whole bloody thing apart, and randomly replacing parts.

FYI, the radiator is not clogged, the thermostats are new and were tested prior to installation, the water pump is pushing water, the entire coolant system has been gone through and functions as it should. Fan shroud is intact, and there is no debris in the cooling fins are between the radiator and charge air cooler. There is no air in the system, and I have installed a coolant recovery tank.

I Am absolutely positive it is fan speed issue, and have verified this. I simply cannot tell how the fan speed is controlled.

 

[Henry J Fate]

Certainly sounds like the fan clutch assembly isn't responding to thermal changes as it should. The thermal spring is responsible for activating the valve gate. The spring responds to temperature and is designed to open and close the valve gate. My guess would be a bad spring and I would probably start with that. At the same time, you will be a able to inspect the rest of the assembly and look for anything that may be causing resistance to the spring and valve gate.

I am not sure what the temperature differential should be on your specific unit but would guess it to be about a 20-30 degree swing and no lower than 180 on a flat road drive. Hopefully someone with specific knowledge of your RV can offer more accurate info.

 

[Gary RV_Wizard]

I doubt if a 1993 vintage has a variable speed fan control - those didn't get common until the early 2000's.  I'm even a bit surprised it is a hydraulic fan drive that switches on/off.  It may be that the fan drive comes on after the engine reaches normal operating temperature (thermostat opens) and after that it relies on a viscous clutch in the fan hub for temperature management. That would be a common approach for a mechanical-control diesel of that vintage.  I've not heard of a system from that era where the fan cycled as you describe. In fact, a common upgrade for those system is to add a fan controller to improve fuel economy. Maybe yours has an aftermarket upgrade of some sort?

 

[Utclmjmpr]

I have the same system as the OP.. The power steering pump drives direct to a hydraulic motored fan that has no controller that I know of. Fan speed is controlled by engine speed. I had to reseal the fan motor with an "O" ring kit imported from Italy 7 years ago and no seepage or problems since.. The fix for over temp is to gear down to unload the engine as needed and this increases the fan speed at the same time,, if that isn't enough then pull over and go to neutral and increase and hold the RPMs at 1800 or more until temps decrease.. Been working for me for 127000 miles.>>>Dan
To the OP: have you checked the hydraulic reservoir or changed the internal filter??>>>

 

[ranger magnum]

Some clarification here...

Firstly, I am well aware of how and why a fan clutch operates, but thank you for the suggestions. I?ve been a mechanic for 30 years, though my specialty is 50?s-70?s GM. I did rebuild the engine in this rv a few years ago; liners, slugs, rings, big end bearings. But that?s another story....

As I mentioned , I do not see a fan clutch assembly. It would need to be a pretty big unit, and I dont see one. Now granted, I?ve not pulled the fan/hydro unit out yet, as that requires removing the trans cooler, charge air cooler, and radiator. I?m not opposed to that, however there is no sense in doing unnecessary work if it can be avoided.

I?ve only read about priority valves/blocks for this type of application, so I?m not sure if I have one. There is a distribution block, so there may be something to that...

There is absolutely, positively something that engages the fan as engine temps increase. It is *not* simply a direct drive that is dependent on engine speed. I?ve been scratching  my head over this for a year, until last month, when the bay doors were open, and the driver window was down. I could hear the fan engage at a constant engine rpm, and increasing/decreasing engine speed had no effect. Only when engine temps fell to a certain threshold did the fan disengage. So something is locking the fan.

There may very well be a fan clutch, but I can?t see one from any vantage point, and given the size of one in my BB Chevy, the rv would need a massive one. I?ve felt around the the fan mounting bolts, and do not feel the telltale ribs of a clutch.

I?m going back to my shop tonight, and come hell  or high water, I?m gonna know if there is a clutch.

If there isn?t, then out comes all the things until I expose the hydraulic motor. I?ll yank it and do a rebuild just because.

And yes, I replaced the filters in the system and filled with fresh Dexron.

Thank the powers that be that I have the tools/space/time/knowledge to do all this stuff. I shudder to think what a shop would ding me with....

 

[Henry J Fate]

Maybe is uses a controller which I think is just a valve that regulates the flow of hydraulic fluid to the fan based on a temperature sensor.

Based on your description of the problem, the fan seems to know cooling is needed but doesn't quite get it right.

 

[ranger magnum]

Exactly Henry!

Now to find out why the fan isnt getting it right!

 

[Gary RV_Wizard]

There are multi-speed fan controllers, but I am all-but-sure a '93 Pace didn't have such a thing. Fleetwood didn't even spec variable or multi-speed fans in their high end coaches (American Dream/Tradition/Eagle) until around year 2000.  I don't remember the diesels using a viscous clutch either, but it's possible.

Ranger has solid observational evidence that the fan engages and disengages at some fixed threshold, but doesn't vary with engine rpm once operating. That's consistent with hydraulic drive rather than engine shaft direct.

Multi-speed hydraulic controllers need management and are usually controlled by an engine computer that can take various parameters into account, but a simple thermostat and one or two speeds is certainly possible. Just a more expensive system that was typically employed on an entry level diesel like the Pace. Will be interested to see if Ranger can find evidence of one.

I'll throw in one more possible wrinkle:  It's a common design for the fan to be 100% engaged while the a/c compressor is running. That's because the fan usually also serves the a/c condensor and air flow is needed for that whenever the compressor is working.
The multi-speed hydraulic fan in my 2004 Fleetwood American Tradition did not begin to spin until the engine reached minimum operating temperature, i.e. the cooling system thermostat opened at 160. When the thermostat opened, the fan began to spin at its slowest rpm, barely moving it seemed. Fan speed increases were based on heat loading from the engine, transmission, and the a/c. The fail safe mode of the fan controller was on at full speed, so if no control inputs were received, that's what it did. So far Rangers observations are consistent with a multi-speed fan control that has failed and runs at full on.  That's why I'm wondering if his cooling system was upgraded from OEM.

 

[Utclmjmpr]

I also have been a mechanic for the most part of my life,,that said, my American Tradition ( on a Spartan chassis), build date 6-97
has a side radiator with a fixed fan bolted directly to the hydraulic motor shaft...Mine was a simple job of unbolting the fan from the motor,, removing the in and out hydraulic lines to access the motor and bingo... After resealing the motor (due to oil seepage)
I set up a test to determine how the system worked..I pasted a reflective spot to one fan blade and measured the RPM movement
with a rev counter,, with the wife's help I varied the engine speed to determine the fan reaction.. The fan speed was dependent on engine speed,,, I knew then how to control temps with my foot and the transmission gearing,, a simple system that works well when understood..  It would be a normal assumption to expect this system to cost you at the pump, but I normally get 10 miles per gallon
+ or - depending on terrain with an 8.3 12 valve mechanical engine and 3060 trans. at 31K all up weight,,Go figure.>>>Dan

To be fair, I have made some changes..I removed the 70 pound muffler,, removed two 90 degree elbows from the exhaust system
and installed a straight thru stainless 4" in 4" out resonator,, and wrapped the system from the turbo out with heat wrap.. This improved exhaust flow and reduced heat transfer to the bedroom area.  I also replaced trans fluid, rear end fluid and front hubs with synthetics .>>> Wish you luck with your dilemma.>>>D

 

[ranger magnum]

Ok, I have more information...

There is no fan clutch. The fan is directly mounted to the hydraulic motor.

What I have is a valve block that takes pressurized fluid from the pump, diverts it to the fan, steering, and brakes. From the valve block it passed through a filter, into the reservoir, and back to the pump. Pretty much a typical system.

On top of the valve block are two electrical connectors, with two wires to each, for a total of four wires. Both wires enter the same loom, and from there to what appears to be something on the top of the transmission. It?s hard to see, and will take some contorted positions to fully examine.

Also on this valve block are some bypass hoses about 3/8 to 1/2? in diameter. These are steel braided lines, so I am assuming they are pressurized as well. One hose goes from the  valve block to a frame mounted valve/pressure switch/whatchamacallit, then back to the valve block. I have some suspicions this is somehow a part of the fan, and this may be a type of priority valve. I am unsure of this, and can only speculate.

The fan definitely engages when coolant reaches a certain temp. At that point, it then spins at engine speed. It will continue to spin in this ?locked? condition until coolant temps drop to a safe level. (I am installing Two electric AutoMeter temp gauges; one on the radiator inlet tube, and one on the outlet. This way I will know not only accurate engine temps, but also the variance between the two.  This way if there is a blockage in the radiator, it will show up. Also, I?m curious as hell as to the differential temps in hot vs cold weather)

As an aside, I too though there may be a correlation between this problem and the aircond, however the ac condenser is located under the rv, and is cooled by two massive electric fans. An odd configuration to say the least.

I could identify and resolve this issue quickly if I could get any help from Fleetwood, but they won?t even answer the tech line, let alone call me back.

And if this were not enough, the Alison TCM took a dump, so I had to sent it out for a rebuild, further delaying my progress. Damn MD3060 WTecII...

Fortunately, the Harley in my living room needs some love, so at least I have something to do in the evening....

 

[ranger magnum]

Also of note, the cooling system does not appear to have been changed or modified, at least from all outward appearances. But again, without any schematic, I have no way to confirm this.

What I do have are service records dating back to the second owner. I?ve seen no reference to any cooling system mods. The third owner was my aunt, but when her husband passed away 3 years ago, she offered the coach to me, which I now have. I asked her if she could recall any instance where the cooling system was an issue, but she had no clue what I was even talking about.

Get an RV they said. It will be fun they said.....

 

[ranger magnum]

Gary,

Excellent points you bring up.

What I believe is going on is some type of lock/unlock system. Almost like the hydraulic fan motor is acting like a viscous coupling. In the unlocked  state, I think the fan spins slowly as a result of fluid passing lazily through the valve block.

Somehow, something ?wakes? up the valve block.

 

[Utclmjmpr]

Which chassis is your coach sitting on,, and do you have a side rad or rear rad.??>>>Dan

 

[Gary RV_Wizard]

I could identify and resolve this issue quickly if I could get any help from Fleetwood, but they won?t even answer the tech line, let alone call me back.

Fleetwood today is literally a different company than the one that built yours, now just a brand name owned by the Rev Group.  I doubt if they even have schematics and records that go back that far, and Rev has drastically curtailed Customer Service and Parts vs the old Fleetwood Corp.  They are pretty much restricting it to coaches less than 5 years old and even those owners are complaining about lack of response.

There is a Pace Arrow Owners Club that may have some info archived or a member who has a coach like yours. You might check it out:
http://www.pacearrowclub.com/

 

[Gary RV_Wizard]

Ranger... Thanks for the additional info - enlightening even though it hasn't [yet] solved your problem.

I'm guessing you have the Oshkosh rear diesel chassis and a Cummins 8.3L, right? If Freightliner Custom Chassis can't help you with the Oshkosh motorhome chassis info, you are probably out of luck.  FCCC bought Oshkosh (which itself bought the chassis from John Deere) back around 1995.  I doubt if Fleetwood ever had a clue about how the engine cooling system actually worked. They were the body builder, not chassis people.

 

[Utclmjmpr]

That's why I asked, I doubted that Fleetwood would have the info because most of the chassis parts were install when Fleet recieved it.. I have gotten better response over the years from Spartan.>>>Dan

 

[ranger magnum]

Success. Les at Freightliner emailed me the schematics for the chassis electrical and the hydraulic schematics as well. And, as I suspected, there is a fan control module. Actually there are two, though they work opposite of one another: if one is energized, there is flow. If the other one is energized, there is no flow.

So now I need to determine which one is which. Also, there is a temperature control switch which tells these modules what to do. I need to see which of these systems is at fault. Fortunately, these parts are available from Vintage Parts, so I may just buy both the sending unit and the modules.

Well, off to study the schematics. I lead an exciting life....

 

[Henry J Fate]

That's good news. Given the importance of the cooling system, it may be a good idea to replace all three components if it is affordable. What kind of money are the control valves ?

 

[ranger magnum]

It is great news. This has taken a lot of my time, and given I was simultaneously dealing with a failing Alison 3060 TCM during a recent two week trip, I was not in the best of spirits.

Now that the TCM has been rebuilt, and will soon regain company with the coach, I can begin the cooling system repair.

There are three parts that are likely in some way responsible for the problems I?ve experienced: the engine temp switch (there are three: the one for the in dash gauge, the one for the coolant overtemp light, and the one that tells the solenoids to open the fluid valves, which is the one in question) and the two solenoids. I?m guessing the temp switch is the culprit, however I?ll not know for sure until I R&I said pieces and bench test.

With any luck by this time next week I?ll know for sure.

As far as cost, I have to order from a licensed Daimler dealer, so you can bet it won?t be cheap when juxtaposed with what I?m actually getting.

I?d be curious to see if this switch cross references with anything else.

 

[Gary RV_Wizard]

Last I knew, you could order parts direct from Freightliner Custom Chassis. I used to call the HELP number to get a part identity, then ask to be transferred to the Parts guy.  Of course, parts this old may not be in stock or even available.

There are some places that handle Oshkosh parts:

https://www.millsupply.com/stepvan-parts/chassis-suspension-steering-driveline/chassis-parts-freightliner-oshkosh-john-deere/chassis-parts-oshkosh-john-deere/

And Advance Auto claims to have an Oshkosh parts catalog:
https://shop.advanceautoparts.com/find/oshkosh-motor-truck-co.-parts

NAPA too:  https://www.napaonline.com/en/heavy-duty-parts/oshkosh