I also have a hydraulic fan motor in my bus. My old motor was showing some slight signs of internal leakage, so when I completely rebuilt my entire cooling system to solve some serious overheating issues I took the opportunity to replace the motor and fan. MultiWing made me a new 9-blade fan that moves a lot more air with a lot less power and noise than the original old metal 6-blade fan that looked like it came from a pre-war Russian farm tractor or something equally archaic, and to help airflow I also reversed the direction of its rotation. The old Webster YC motor was replaced by another YC, custom-made by Quality Control Corporation, but on the first test-drive after installing it the entire motor casing split apart after just six miles! It took a month of arguing with QCC until they finally agreed to make me a replacement, only because they couldn’t prove that the failure was of my making. To ensure that nothing like that ever happens again I installed a Prince RD-1875H pressure relief valve that prevents the motor getting more than 1500 PSI, and I also replaced the Danfoss 7WA110-2 solenoid directional control valve assembly that controls the motor speed - I found someone on eBay selling them for only $35 each (originally they were almost $800 each!), so I bought his last three and now have two spares for the future. To ensure the new motor receives as much flow and pressure as possible, I also replaced the old Webster KB hydraulic/PS pump with another (only $135 from eBay!) and reused the priority flow divider valve assembly off the old pump that was still good; if I had bought exactly the same complete pump as before it would have cost more than $1000, so using the old flow divider saved me about $900. Yeah! The old pump’s drive gear and gear coupling were very badly worn: I’m glad I changed them out when I did otherwise they could have failed on the road with dire consequences. I replaced some of the low-pressure hoses and both the high-pressure hose assemblies, moved the hydraulic fluid cooler to a new location next to my new transmission fluid cooler, added a Baldwin 10-micron filter to the motor’s return hose just before the reservoir, and put two pressure gauges on the motor’s feed and return lines to tell me now exactly what pressures it’s seeing.
Yes, it was a lot of work, along with having a new high-efficiency radiator core made by Atlas Radiator, powder-coating the radiator tanks and the coolant surge tank, reinforcing the radiator’s mounts, thoroughly re-sealing the radiator shroud to prevent any air from leaking past the core, adding three new temperature gauges to tell me the temperature of each cylinder bank and the radiator outlet, replacing both thermostats and their seals and housing gaskets, and finally making a distilled-water mister system for the radiator just in case I still need some extra cooling when climbing long grades in hot weather. At this point the engine cooling is where I want it to be, but I’m still toying with the idea of adding an entirely separate second radiator on the opposite side to take care of unusually hot conditions, such as climbing I-15’s Baker Grade in 115-degree heat, not uncommon in the Mojave Desert. We’ll see - there’s always another project or two to think about!
The subject of replacing stock cooling systems’ fans with electric fan motors is perennially discussed on the BCM forum and elsewhere, and the general consensus of thought is that they will not provide sufficient cooling capacity for over-the-road use, especially in hot weather. What works for city transit buses in stop-and-go use will not be adequate for continuous long-distance use, and everyone who’s tried electric fans has not had happy results (or worse). A RE bus fan takes as much as 40 HP to drive it - there are no electric fans that will move as much air continuously as an OEM system, regardless whether it’s direct-drive with a torus such as GM used for their V-drive buses, belt-drive such as used by MCI, shaft-drive used by Eagle and others, or hydraulic drive used in school buses and transit buses. Many folk have tried over the years to make an effective electric fan drive for RE buses, but I’ve never heard of one working well. Remember that what is OK for a front-engine truck is not OK for a RE bus that has no ram-air effect at speed - all the bus's air must be pulled in at 90 degrees from its flow direction, a very hard task.
John
