[MrE]

Interesting thread, the mechanic doing my re-power talked me out of using the hydraulic setup from the donor bus.
"The fan is going to be belt-driven so as to move more air than the hyd system the city bus set up could. I got a fan gearbox from Prevost. Almost done with that and then will pull rad back out and have it recored"

   

[ccjohnson]

You should be up and running pretty soon!

[Richard]

Well……rats.

The seal started leaking for the third time during our summer trip. ATF really does make a mess. You know the engineers definition of insanity, doing the same thing over and over but expecting a different outcome.

I had some communication with the engineers at Zero Max, the manufacturer of the OHLA. The version we have is a Newell special. They normally come packed with grease, instead of having an flow through lubrication system. Newell did it in a very clever way by routing the drain hose from the hydraulic motor through the OHLA and then routing the outlet from the OHLA to the hyd reservoir. So, taking the OHLA out the loop will mean the case drain from the hyd motor will now go directly to the hyd reservoir. 

But I am tired of cleaning up that mess in the engine bay, so here is my conversion to grease filled OHLA. I used Mobil 1 SHC grease, that is why it is red in the pics.

The first pic is of the OHLA with the original JIC hydraulic fittings. These are kind of different fittings than I knew about, but I learned they are JIC on one end and ORB on the other. ORB stands for O ring boss. It is supposedly a tighter seal, but only if you can tighten the nut to make the seal between the O ring and the case. Picture two shows the old fitting removed. Those marks on the nut are where someone in the past tried to tighten it with a hammer and a punch. No way a socket or wrench is getting in there because of the right angle.

Anyhoo, I replaced the right angle fittings with a #10 ORB plug. I drilled and tapped a hole in both the plugs and installed zerk fittings prior to installation. I removed the drain plug on the top and replaced with a vent plug. I did spring for new seals although that may have been overkill with the grease.

I will provide an update after next years tour of the country.





Oh yeah, one more thing, if you ever try this. The original plug on the top of the case was 1/4 NPT with an Allen recess. After breaking two Allen wrenches, I knew it wasn’t coming out. So I found a big nut that would just fit over the plug, and plug welded the nut to the plug. No problem removing after that. This is technically known in the south as the mo powah technique.

[Latitude 28]

Richard, Great news.....looks like another project coming my way. When you separated the OHLA from the Hyd Pump, what kind of shaft arrangement is on that end of the OHLA?

[Richard]

Tapered and keyed shaft on the fan hub side. Splined slip fit between the hyd pump and the OHLA.

[Georgeb]

engine hydraulic fan is not turning
Should it run at slow speed and speed up as engine
Temp rises?
My fan runs at high speed if I unhook at the control
But nothing at idle I’m I’m

[Richard]

Many of them barely spin at idle. It may or may not spin as you increase RPM. If it goes to hurricane mode when you unplug the solenoid, the control system is working properly.

It does NOT increase speed with temperature UNTIL the Temp reaches 203, then it goes to HIGH. It is a two speed control system, not a proportional one.

Are you overheating?

[Georgeb]

Not overheating
I started it up this AM ran at high idle for a while, it’s 
Way hot here, temp on dash gauge went up to 200. 
I walked to rear of coach and didn’t hear fan. I opened
Rear hatch and fan was not turning. I unplugged the wire
To control and fan went to high speed.
I thought fan should be moving???

[Richard]

Dash gauges are notoriously inaccurate.

Fan may not turn on low speed control. Keep in mind air is drawn in radiator and exits rear hatch while going down the road due to low pressure area behind the coach

[kaptain]

Thanks to Richard and all who shared useful information in this thread.
I discovered I have a hydraulic leak at the fan motor too. Initially, it looked like a coolant leak because the leaked fluid was red, the same color as the coolant, and the coolant tank is on top of that fan. A tip from Richard responding to my post convinced me it's a hydraulic leak.

I first cleaned that area and returned the next day and saw leaked fluid there again. Now it's clear to me it came from the gap of a hex screw or Allen socket screw.
According to the manufacturer of this OverHung Load Adapter, Zero-Max, this socket screw has 1/4-18 thread, but no documentation showing how long this screw is, and overtightening it could result in the screw touching or blocking the bearing of the adapter.

I was considering replacing this screw today, but I realize removing this hex screw will result in some mess due to a lack of a valve to shut down the drain of hydraulic fluid. So on the 2nd thought, I'll order a set of Hex Head Pipe Plug Fittings (which contains 1/4 size, and I hope the thread matches).
https://www.amazon.com/gp/product/B095YCY85S/

I was hoping to find some plugs with an o-ring and a larger head to achieve a tighter seal, but I didn't find any.
I will provide an update with the final results later.

Leak Found
   

Leak Fluid Cleaned
   

I came back the next day and saw the same leak again. Now it's clear the leak came from the edge of the hex screw on top of the Overhung Load Adapter.
       

Cleaned again and sing a 6mm (better with 1/4) hex wrench to tighten this screw.

   
Replacement plugs ordered
   

Zero-Max made Overhung Load Adapter specifications.

L600130-OCR.pdf Size: 25.88 KB  Downloads: 19