LMTV Cat 3116 Issue >> Fan always on <<

[Alexandninasdad]

I have been on You-tube trying to get a rudimentary understanding of how that Air pressure regulated fan system and control switch works. I thought it wise to post here and see if anyone else had a simple troubleshooting advice for > Fan always on < Issue.

So far I have:

> Found the solenoid my the Pax kick plate and during a recent Highway Run .. tapped it to get the fan to come on ( when temp was climbing ) .

> Disassembled and lubed that solenoid with PTFE

> Tested the Fan switch which does turn "off " or disconnect at 200 F

> Replaced the Thermostat ( 80 C )

> Checked the Fan ( Engine off / no air pressure ) and the fan is rock solid no give or wiggle whatsoever.

> Gone thru the entire Air charging system and replaced various and sundry items to include the Governor , unloader valves and the Dry-er .

Any thoughts , shortcuts , wisdom or dry humor is appreciated.

Email: Adversityrevealscharacter@gmail.com

 

[frank8003]

wow, I remember this subject was just about beat to death in SS
Look around in here.................

 

[Alexandninasdad]

wow, I remember this subject was just about beat to death in SS
Look around in here.................

Okay .. will do .. ThanQ

 

[Andyrv6av8r]

> Found the solenoid my the Pax kick plate and during a recent Highway Run .. tapped it to get the fan to come on ( when temp was climbing ) .

So you're saying at one time the fan was off, as in free-wheeling? Tapping the solenoid made it engage and " come on "?

 

[Alexandninasdad]

OK to clarify .. here is the rest of the story. I previously omitted these details to protect my pride. So here goes ! Im on a highway run and bringing the truck back from the shop that mated the Living Module to the Chassis in South UTah. Everything is Great .. until it isnt. Temp gauge climbs but the placement of the gauge is hidden by the steering wheel and i dont see it right away. I pull over to let things cool down to limp back to home base .. and I notice oil all over the drivers side / Battery Box. However I'm clueless and limp on to the nearest Diesel Shop up the way.
Well ! The shop seems to have plenty of work going on and the Old diesel guy looks and diagnoses a stuck injector. .. which was over-fueling. Recommends NEW Injectors. Those @$^*%#@$ took a whole month to pry $3700 out of my pocket. I feel like a complete idiot.

So NEW Injectors IN .. All my Money >> OUT ! I'm not smart enough to know whether overheating caused the stuck / over-fueling injector or if the overheating was the result of the injector sticking and over-fueling. What I DO know is that heat will destroy my Engine so I religiously keep tapping the Solenoid every time the temp climbs and i make it back to Home base.

More light on the subject .. im clearly a half wit in the weeds .. and in over my head. It's my first time digging into a Electric & Air driven clutch cooling system that connects when current is off. Its a lot to get my head around. BUT i do learn best with my hands dirty and grease up to my elbows.

My most recent Inquiry : Master power on, Air System Charged, Engine > OFF =
RESULT the Fan spins freely and there is no wobble or give. I THINK according to posts i've chewed thru here my Cooling System is good to go ( Or no ?? )

 

[NDT]

News flash: FMTVs are like a Harley, every few hundred miles you have to stop either for repairs or to reassemble them. Best to learn how to turn wrenches and perform diagnostics.

 

[Andyrv6av8r]

My most recent Inquiry : Master power on, Air System Charged, Engine > OFF =
RESULT the Fan spins freely and there is no wobble or give. I THINK according to posts i've chewed thru here my Cooling System is good to go ( Or no ?? )

Not really. In that configuration the fan should turn. It doesn't mean that the solenoid is venting properly and locking the clutch/fan. You need to do more troubleshooting. My phone number is in my sig line if you need help.

 

[frank8003]

Where is the guy that said it is all in the TM,s
I think He be a general or above. Follow orders.
Understand the TM's
No one has enough money, why blow yours away too.

 

[Alexandninasdad]

Not really. In that configuration the fan should turn. It doesn't mean that the solenoid is venting properly and locking the clutch/fan. You need to do more troubleshooting. My phone number is in my sig line if you need help.

ThanQ I will look thru the Tm's to assess that Solenoid for proper function.

 

[Ironcladz]

Having the same issue my fan is always on. My water temp gauge also just stays at 250 on or off.

 

[Andyrv6av8r]

Having the same issue my fan is always on. My water temp gauge also just stays at 250 on or off.

Done any troubleshooting? If your temp stays at 250 with the fan on, you have other issues.

 

[Mullaney]

Done any troubleshooting? If your temp stays at 250 with the fan on, you have other issues.

.
250 is kinda warm for sure!
Maybe the gauge is wrong?
Maybe the sending unit is lying...

Maybe a cheap thermometer gun so you can zap the hose or a few spots on the cooling system to see what the real temperature is?

 

[Autocar]

I don't know the slightest thing about Cats, but my Cummins M916A1 had the same problem. I assume all the trucks use the same air clutch made by Bendix. How it works is there is a spring loaded cone clutch that presses against the inside of the fan pulley locking the fan hub to the fan pulley. There is also an air piston inside the fan hub. When air is applied to the piston, the piston moves the hub forward which releases the fan clutch from the hub so it freewheels. When the engine gets up to temp, the fan thermostat valve shuts off the supply air off to the piston and simualtaneously dumps the existing piston pressure. The clutch engages the hub and fan so the fan spins. It spins until the engine cools below the thermostat setting at which point, it opens up and supplies air to the piston thereby moving the hub and freewheeling the fan again. If it sits for any amount of time, the clutch frictions rust or stick to the fan pulley so the fan won't freewheel.

Remove the air line to the fan clutch and attach 100-130 PSI shop air directly to the clutch with the engine off. You should be able to spin the fan by hand. If not, the fan pulley is stuck to the clutch hub. You will have to remove the fan and fan clutch unit and disassemble it to clean and lube everything up. You may have to hammer the pulley get it loose from the clutch frictions. If you don't use the truck often, it will lock up again. It sounds complicated, but it is really straightforward when you get into it.

 

[Mullaney]

I don't know the slightest thing about Cats, but my Cummins M916A1 had the same problem. I assume all the trucks use the same air clutch made by Bendix. How it works is there is a spring loaded cone clutch that presses against the inside of the fan pulley locking the fan hub to the fan pulley. There is also an air piston inside the fan hub. When air is applied to the piston, the piston moves the hub forward which releases the fan clutch from the hub so it freewheels. When the engine gets up to temp, the fan thermostat valve shuts off the supply air off to the piston and simualtaneously dumps the existing piston pressure. The clutch engages the hub and fan so the fan spins. It spins until the engine cools below the thermostat setting at which point, it opens up and supplies air to the piston thereby moving the hub and freewheeling the fan again. If it sits for any amount of time, the clutch frictions rust or stick to the fan pulley so the fan won't freewheel.

Remove the air line to the fan clutch and attach 100-130 PSI shop air directly to the clutch with the engine off. You should be able to spin the fan by hand. If not, the fan pulley is stuck to the clutch hub. You will have to remove the fan and fan clutch unit and disassemble it to clean and lube everything up. You may have to hammer the pulley get it loose from the clutch frictions. If you don't use the truck often, it will lock up again. It sounds complicated, but it is really straightforward when you get into it.

.
Nice writeup Autocar !

That's a lot like the S & S trucks and their brake shoes that rust to the drums.
Same story if they sit around too long without being driven.

 

[Autocar]

.
Nice writeup Autocar !

That's a lot like the S & S trucks and their brake shoes that rust to the drums.
Same story if they sit around too long without being driven.

Thanks. It locks up very quickly. Didn't start it up for 6 months and it locked up again even though we're in California with dry air so there should be minimal rust. Only good thing is it didn't cost anything to fix. Just be careful not to ruin the o-rings or damage the bearings.

 

[HDN]

I don't know the slightest thing about Cats, but my Cummins M916A1 had the same problem...

Thanks for the explanation! I have a Cat 3116 in my M35A3 and it seems to work the opposite you describe. When I first start the truck, it has no air in the system and the fan freewheels, so I think air is needed to actuate the clutch to engage the fan. The fan clutch is a grease point on my A3, although hard to get to It looks like making sure that clutch is well-greased is key to keeping it from malfunctioning!

 

[frank8003]

Thanks for the explanation! I have a Cat 3116 in my M35A3 and it seems to work the opposite you describe. When I first start the truck, it has no air in the system and the fan freewheels, so I think air is needed to actuate the clutch to engage the fan. The fan clutch is a grease point on my A3, although hard to get to It looks like making sure that clutch is well-greased is key to keeping it from malfunctioning!

and was designed to use GAA?

 

[HDN]

and was designed to use GAA?

According to the lube order, yes. The LO calls it an "Accessory Drive Pulley".

 

[Autocar]

Thanks for the explanation! I have a Cat 3116 in my M35A3 and it seems to work the opposite you describe. When I first start the truck, it has no air in the system and the fan freewheels, so I think air is needed to actuate the clutch to engage the fan. The fan clutch is a grease point on my A3, although hard to get to It looks like making sure that clutch is well-greased is key to keeping it from malfunctioning!

Sounds like a dumb design doesn't it? The Bendix unit is a "fail safe" design. Since the clutch is spring loaded to engage, loss of air pressure for any reason results in the fan being on. If air is required to engage the fan, loss of air pressure results in the fan being off which would cause overheating.