Fan Clutch Troubleshooting

[NMC_EXP]

Last winter the M1009 cab did not warm up too well. This winter it was worse. I could drive the 30 miles to town at 55 MPH in 25 degree weather and the radiator and hoses were barely warm.

Replaced the thermostat with the correct 195 deg hockey puck and that made a very small difference but still no good for cabin heat.

Been real cold around here so I put cardboard in front of the grill. Couple of days ago it was 7 degrees. I started the M1009 and when I put the cardboard in place I noticed the fan was drawing enough air to suck the cardboard in against the grill.

Made me think of the fan clutch. Checked the -20 TM and all it says is "check fan clutch" and "replace fan clutch". The TM does not explain how to "check fan clutch".

Just found a thread about a cold CUCV. Someone said with the engine cold and off the fan should spin freely. This makes sense and I'll assume it is correct. I'll give that a try.

Questions:

1. How does the CUCV fan clutch work? I'd just like to know

2. Does the CUCV fan clutch contain a fluid which can be topped off or changed to get it working rather than replacing the fan clutch?

Seem to recall the fan clutches on vintage Toyota Land Cruisers contain a fluid which if low can cause it to be inop. The fluid can be topped off to get it functioning.

Thanks

Jim

 

[doghead]

http://www.haydenauto.com/fan clutch tutorial-part 1/content.aspx

It is not serviceable.

I question your radiator and heatercore. Have you flushed them?

 

[Skinny]

If the engine hoses are not warm this is probably the place to start. With the engine cold and not running is the fan very stiff to turn or able to move at all? This would indicate the clutch being seized up. I would venture as far as to remove the fan and drive it to see if it warms up. Of course the Cucks have no temp gauge so do this at your own risk. If it heats up you found your problem. I wouldn't hesitate to backflush the heater core just for good measure.

I will tell you that my M1031 makes good heat in that temperature with no grille cover while driving at low and high speeds so you should be having no problem maintaining engine operating temps.

 

[scottladdy]

Let's start simple. The stock heating system on the GM Square Body trucks is dead simple.

1. Coolant is always running through the heater core on a properly functioning system regardless of cab temp setting.
2. The cab temp setting changes the position of an air blend door that directs more or less outside air over the heater core.

Back to the first point. After the engine has warmed up, the heater hose running from the passenger side of the coolant crossover should be warm. It should actually warm up fairly quickly. The crossover should be nice and toasty on the passenger side as well.

Be careful of the fan!!!!!!!

Let's start there. Test and let us know what you find.


FYI, The nipple on the crossover has a flow reducer in it.

 

[Skinny]

The OP has a new thermostat and the hoses are cool after warm up and drive time. It sounds like the engine can't generate heat at this point.

 

[scottladdy]

The OP has a new thermostat and the hoses are cool after warm up and drive time. It sounds like the engine can't generate heat at this point.

Respectfully, let's see what he finds doing careful methodical testing. One step at a time.

If that engine is running, it is generating waste heat. No ifs, ands or buts. That heat must be going somewhere. No choice. Otherwise that truck would be overheating. You cannot defy the laws of thermodynamics.

If the thermostat is properly installed and functioning within tolerances, there are no issues with the water passages in the block, there is sufficient coolant, and the water pump is moving coolant, that crossover must be getting hot. Not an option.

Now, if the thermostat is stuck open or not functioning ...

New parts can be installed incorrectly and can also fail.

Let's follow a methodical diagnostic trail to find the issue. Making an assumption that a replaced part is good without proving it almost always leads to many extra hours of diagnostics and wasted money.

Respectfully submitted ...

 

[NMC_EXP]

http://www.haydenauto.com/fan clutch tutorial-part 1/content.aspx

It is not serviceable.

I question your radiator and heatercore. Have you flushed them?

To bad re: fan clutch being non serviceable.

The cooling system has not been power flushed - drained and fresh fill only. They may well be cruddy.

My first impulse is overcooling because after driving 30 miles at 55 mph in 15 to 20 degree ambient temp the radiator, hoses and engine are what I would call just warm to the touch.

I checked out the link you provided - thanks. I've managed to learn something about fan clutches. The tutorial did raise another question though: Is the CUCV fan clutch the "non-thermal" or "thermal" type?

From what I read if it is non-thermal it will suck air when the engine is cold (my M1009 does this). If it is thermal the fan is disconnected when the engine is cold.

Thanks

Jim

 

[doghead]

They are non-thermal.

Here's a thread that has some good info also. http://www.steelsoldiers.com/showthread.php?105566-Radiator-Fan-Shut-off

 

[NMC_EXP]

If the engine hoses are not warm this is probably the place to start. With the engine cold and not running is the fan very stiff to turn or able to move at all? This would indicate the clutch being seized up. I would venture as far as to remove the fan and drive it to see if it warms up. Of course the Cucks have no temp gauge so do this at your own risk. If it heats up you found your problem. I wouldn't hesitate to backflush the heater core just for good measure.

I will tell you that my M1031 makes good heat in that temperature with no grille cover while driving at low and high speeds so you should be having no problem maintaining engine operating temps.

I'll do some troubleshooting tomorrow. Doghead attached a link to a tutorial about fan clutches so I learned something but it also raised another question - is this one a non-thermal or thermal fan clutch?

This unit has been my DD for 3 years now. Cabin heat has never been anything to brag about but is worse this winter than before.

I'll reserve removing the fan as a last resort. If I had a coolant temp gage I'd give it a go.

Just thought of something else - this truck loves hot weather. It acts like a different machine when air temp is 80 deg or better. The engine is quieter, smoother, more power, and higher MPGs. Once air temp drops below 50 deg I notice a big difference. Could be it has been overcooling all along.

Thanks

Jim

 

[Nuke113]

For what its worth my M1028 was doing exactly as you describe being just warm to the touch after a long drive and this was cured by a thermostat. If your cross over remains cold I would pull the thermostat and throw it in a pot of water and make sure its working right.

 

[NMC_EXP]

They are non-thermal.

Here's a thread that has some good info also. http://www.steelsoldiers.com/showthread.php?105566-Radiator-Fan-Shut-off

CUCV = non-thermal fan clutch.

Therefore it will suck air when the engine is cold - just like this one does now.

From what I've seen a non-thermal clutch is purely dependant on RPM and has nothing to do with temperature.

Thinking out loud:

--If the fan clutch failed such that the fan ran full speed at high engine RPM seems like the thermostat would just stay closed more and still maintain the coolant temp at 195 deg.

--If the fan clutch failed such that the fan free wheeled all the time then overheating while idling the engine/vehicle would be a possibility.

Question: Assuming a 195 deg thermostat was installed right and functioning would you expect the coolant temp to reach 195 deg after driving 30 miles at 55 MPH with an ambient temp of 20 deg.?

Thanks again

Jim

 

[doghead]

Yes, I would expect that to occur.

 

[scottladdy]

Yes, I would expect that to occur.

I concur ...

 

[NMC_EXP]

Let's start simple. The stock heating system on the GM Square Body trucks is dead simple.

1. Coolant is always running through the heater core on a properly functioning system regardless of cab temp setting.
2. The cab temp setting changes the position of an air blend door that directs more or less outside air over the heater core.

Back to the first point. After the engine has warmed up, the heater hose running from the passenger side of the coolant crossover should be warm. It should actually warm up fairly quickly. The crossover should be nice and toasty on the passenger side as well.

Be careful of the fan!!!!!!!

Let's start there. Test and let us know what you find.


FYI, The nipple on the crossover has a flow reducer in it.

I appreciate this and your post #6. I will go thru the steps you mentioned ASAP.

Doghead provided info on fan clutches and based on that info I now doubt that is the problem - seems like the thermostat ought to be able to compensate by staying closed to keep the coolant at 195 deg even if the fan is running 100% at highway speed.

1. The cab temp setting changes the position of an air blend door that directs more or less outside air over the heater core.

I looked at the -20 TM section 10-13 for the cabin heater. I see the where the tmp control cable and temp control shaft are located on the heater assembly.

Question: is it necessary to remove the heater assembly from the firewall to get at the temp control door? The TM does not go into detail.

Thanks

Jim

 

[scottladdy]

Is the CUCV fan clutch the "non-thermal" or "thermal" type?

You can easily tell if your clutch is the thermal or non-thermal type. The face of the clutch closest to the radiator will have a bi-metallic thermostatic coil spring at the axis (center) of the clutch. Coil spring = thermal. No coil spring = non-thermal.

AC Delco online catalog replacement indicated for our trucks (3 speed auto) is as follows:

CLUTCH ASM-FAN BLADE
Part Number: 15-4599
Product Notes:
Engine Cooling Fan Clutch
Radiator,Heavy Duty,Includes Heavy Duty Transmission Oil Cooler (V02); Code Dt ; Thermostatic ; Transmission 3 Speed Trans Automatic ; Trans; Code: THM400 ; 1 Per Veh

Per Vehicle: 1; Years: 1983-1986

Both my CUCV's have a coil spring up front.

Hope this helps ...

 

[NMC_EXP]

Yes, I would expect that to occur.

doghead and scottladdy

If the new thermostat was installed upside down would it act as though it were wide open all the time?

Regards

Jim

 

[scottladdy]

Question: is it necessary to remove the heater assembly from the firewall to get at the temp control door? The TM does not go into detail.

I guess it depends on what you are trying to do.

If you want to check to see if the cable is actuating the door, you just need to look under the dash and watch as you move the lever.

If you want to see what condition the door is in then I see no other options but to remove the assembly from the firewall.

Maybe some others on the forum have had a different experience?

 

[NMC_EXP]

I guess it depends on what you are trying to do.

If you want to check to see if the cable is actuating the door, you just need to look under the dash and watch as you move the lever.

If you want to see what condition the door is in then I see no other options but to remove the assembly from the firewall.

Maybe some others on the forum have had a different experience?

If the cable is moving the shaft then it is probably OK. I suspect there is some sort of seal on the door which is crumbling or long gone and would let air into the core.

I'll check the door situation as well.

May not be able to do this stuff tomorrow - have a wedding anniversary conflict. We'll take her 4Runner rather than the M1009. The heater in that thing works fine.

Jim

 

[scottladdy]

If the cable is moving the shaft then it is probably OK. I suspect there is some sort of seal on the door which is crumbling or long gone and would let air into the core.

I'll check the door situation as well.

May not be able to do this stuff tomorrow - have a wedding anniversary conflict. We'll take her 4Runner rather than the M1009. The heater in that thing works fine.

Jim

Let's start by checking how hot that crossover and heater hose are getting. That will narrow down where to look next. Should take 15 minutes or so.

Enjoy the anniversary celebration!

 

[doghead]

doghead and scottladdy

If the new thermostat was installed upside down would it act as though it were wide open all the time?

Regards

Jim

I'm sorry, I can't answer that.