Cat 730 Fan Motor Slow B1M Serial

[Company Wrench]

The fan is too slow on my B1M prefix truck. With the fan solenoid unplugged it only turns 780 RPM at low and high idle. The hydraulic pump has 300 hours on it; I tested the pressure and it's good (3,000 psi) on both pumps 1 & 2. I exchanged the diverter valve on the MCV and put a new o-ring kit. The fan solenoid entire assembly was replaced with new. The relief valves were both rebuilt with new o-rings. I attempted to pull 1 of the 3 screens but the cap was stripped so I am working on that. Wanted to see if anyone has experience with this? Thinking I could rebuild 2 shuttle valves and 2 check valves because if they are washed out they could be letting fluid by. Also, the main control valve was super hot the other day when I noticed the fan not kicking on a during operation. The o-rings removed so far have been brittle and broken in some cases- washed out. This circuit is pump 1; brake/fan/hoist. Thinking it could also be related to be lift hoist if some orings are washed out there also allowing fluid back to tank but it functions fine. There were not other symptoms other than slow fan speed and thus heat, creating some oil leaks from the heat.

 

[DieselFit]

I haven't looked at the schematic again, but that main control valve block under the cab has a few shuttle valves underneath the fittings that tend to get little pieces of hardened o-ring in them which jams the ball from moving, which may be stopping the fan circuit from upstroking the pump. If the hydraulic system has been hot for a while, it may be best to remove that valve block & change the million o-rings in it & clean out the passages.

 

[nikthewho]

Hydraulic schematic would help a lot

 

[Company Wrench]

Hydraulic schematic would help a lot

https://www.heavyequipmentforums.com/attachments/renr8034-03-hydraulic-schematic-pdf.354936/

 

[Company Wrench]

I haven't looked at the schematic again, but that main control valve block under the cab has a few shuttle valves underneath the fittings that tend to get little pieces of hardened o-ring in them which jams the ball from moving, which may be stopping the fan circuit from upstroking the pump. If the hydraulic system has been hot for a while, it may be best to remove that valve block & change the million o-rings in it & clean out the passages.

Thank you sir, I posted a schematic compliments of Nige.. Page 8. I agree it's best to pull it and rebuild it but I am trying to get the unit operational and have done a significant amount in the field. Rather try the last few options before pulling it, as it is quite the job in the field.

 

[Company Wrench]

Hydraulic schematic would help a lot

Thank you sir, I posted a schematic compliments of Nige.. Page 8.

 

[nikthewho]

https://www.heavyequipmentforums.com/attachments/renr8034-03-hydraulic-schematic-pdf.354936/

Cannot open the link.

 

[Gary Layton]

Same here...I get the same message.

 

[Nige]

Here ya go.