5 ton 923A2 overheating

[CARMAN]

Took the local Boy Scout Troop out yesterday to put out flags down the main street in town. No ladder required when standing in the back of the 923. It's 100+ degrees here and the truck was running hot. When I got home noticed fan not spinning. Question...If the truck is parked and has been drained of air should the fan be locked up? I think that is what I read? Worried because I am to have it in a parade Wednesday.

Edit...Looked through other threads. Looks like I need to start with the bypass. Assume the fan should free wheel when no air is applied.

 

[simp5782]

Took the local Boy Scout Troop out yesterday to put out flags down the main street in town. No ladder required when standing in the back of the 923. It's 100+ degrees here and the truck was running hot. When I got home noticed fan not spinning. Question...If the truck is parked and has been drained of air should the fan be locked up? I think that is what I read? Worried because I am to have it in a parade Wednesday.

Edit...Looked through other threads. Looks like I need to start with the bypass. Assume the fan should free wheel when no air is applied.

Free wheel unless its engaged. Go to your local hydraulic shop and ask for a #6 jic union. It will allow you to hook the hoses together. If you need a shutterstat let me know I've got a few takeoffs.

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[CARMAN]

Won't have time to diagnose till tonight when I get home. With only 16K on the truck should I have you send me one? Have to drive truck south tomorrow for parade on Wednesday.

 

[simp5782]

Won't have time to diagnose till tonight when I get home. With only 16K on the truck should I have you send me one? Have to drive truck south tomorrow for parade on Wednesday.

You should get a jic union anyway for emergency and put in your map box. Doubt it would get there in a day. The jic would allow your fan clutch to stay on all the time. So you should be fine on overheating. You did check your coolant level correct? You also verified the engine temp with an temp gun over trusting your dash gauge correct?

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[CARMAN]

Yes, and yes. Also want to add that cut off to the heater core cause i'm getting fried in the truck. Can I just put a cut off on one side?

 

[74M35A2]

The fan pulls 15hp when running at 2,000rpm. You really only want it running when it needs to. In a parade, OK, but on the freeway, it is going to suck a lot of power and fuel, and for no reason. Should not take long to diagnose. Also, when you say it was running hot, was it over 200F? The fan switch for an A2 turns on at about 200F, and back off at 190F or so (the NHC-250 switch has slightly lower trip points I believe). Could there be a chance it is not really running hot, but instead just hotter than you think (stock thermostat setting is 180F). Could also be a thermostat issue, of which constant fan engagement won't help much.

There are self storing bolts in the fan clutch, you change their position to create direct drive if you want, air bypass of thermal switch is probably easier though if your thermal switch is the issue. Modern trucks have a pneumatic fan clutch, but it defaults to locked-up with no air pressure, and takes air pressure to release it (fail-safe).

Yes you can block just one hose path of the heater core, there are valves for both in case it leaks to stop coolant loss.

 

[CARMAN]

At fleet pride. These guys say they don’t stock #6 jic union. Act like I’m crazy. What’s the thread size. #6 says 3/8. Another thread said 1/4

 

[CARMAN]

Truck was a constant 210 yesterday and fan never engaged

 

[simp5782]

At fleet pride. These guys say they don’t stock #6 jic union. Act like I’m crazy. What’s the thread size. #6 says 3/8. Another thread said 1/4

You need to call a hydraulic shop. Not fleetpride. It's a #6 jic Male union. The hose is 1/4" the shutterstat uses 1/8" pipe fittings in its body. JIC is the hose fittings though. Or you can remove both fittings from the shutterstat and use a 1/8" female coupler and put both of those fittings together like that. Takes longer and alot more work

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[CARMAN]

Cool. At Tipco

 

[CARMAN]

Ok. Found the heater core shut off. Thanks. Going to bypass shutterstat. Should I blow air down the lines to clean out?

 

[CARMAN]

Ok. So fan locked up almost immediately. So that’s good. Going to put it back to normal until parade.

 

[CARMAN]

You need to call a hydraulic shop. Not fleetpride. It's a #6 jic Male union. The hose is 1/4" the shutterstat uses 1/8" pipe fittings in its body. JIC is the hose fittings though. Or you can remove both fittings from the shutterstat and use a 1/8" female coupler and put both of those fittings together like that. Takes longer and alot more work View attachment 733111

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A2 truck uses #4 JIC

 

[simp5782]

A2 truck uses #4 JIC

Weird. Mine has a #6. Nhc250 trucks use a #6 and #5 jic

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[CARMAN]

I’m glad I bought both as I don’t live close to those stores.

 

[1 Patriot-of-many]

https://www.steelsoldiers.com/showthread.php?143231-92-shutterstat-fan-clutch-actuator/page5 Mine turned out to be a clogged up elbow at the shutterstat.