Fan Clutch

[nspctr1]

I was following another post about low power in the 6.2 and someone mentioned that either the cadillac valve was bad or the fan clutch was stuck. I checked the voltage at the valve and have 24V so I am assuming it is operating as it should. I tried turning the fan by hand and it is stuck? in position. I put a bit of pressure on the back side of the fan at the clutch and got it to move a little but its not free. My question is, should the fan turn freely when the motor is not running? When the truck is running the fan powers on at about 210 or so, so it appears that it is operating correctly.

Thx

 

[3jacks]

It should not free spin with engine off.

 

[orgnal]

I was following another post about low power in the 6.2 and someone mentioned that either the cadillac valve was bad or the fan clutch was stuck. I checked the voltage at the valve and have 24V so I am assuming it is operating as it should. I tried turning the fan by hand and it is stuck? in position. I put a bit of pressure on the back side of the fan at the clutch and got it to move a little but its not free. My question is, should the fan turn freely when the motor is not running? When the truck is running the fan powers on at about 210 or so, so it appears that it is operating correctly.

Thx

Based on what you are stating, it sounds like it is working like it should.

McReddy

 

[nspctr1]

Just want to make sure because I read in another post that said if you unplug the cadillac valve that the fan clutch should move about a half an inch. When I unplug it, nothing happens. There is power to the valve also.

 

[Bravojmc]

Just want to make sure because I read in another post that said if you unplug the cadillac valve that the fan clutch should move about a half an inch. When I unplug it, nothing happens. There is power to the valve also.

sounds like it's compressed air time! Like the clutch isn't working.

 

[Action]

Do you hear a loud noise when you unplug that connector? Do it on a cold engine so you know the fan shouldn't be engaged when you do the test.

 

[nspctr1]

no noise. engine cold. I pulled the hose from the fan shroud and its full of PS fluid. how do you blow air through the system without making a mess?

 

[86humv]

Make sure eng. is running before you unplug connector...doing so without truck running wont do anything.
With eng. off fan is engaged, so it wont move.
Hydralic pressure disengages fan when cold if working properly.
When eng. is hot and system working properly....cadillac valve cuts hyd. pressure to engage fan.

 

[nspctr1]

I see. That makes sense. Thx. Will try this evening and report back

 

[Action]

If you want to put air in the clutch, leave engine off.

 

[kcobean]

I've been trying to figure out this system as well. Is this summary of operation correct:

- The default condition of the clutch is "engaged" so when the engine is off the fan will not turn because the fan is "linked" to the engine via the clutch (and belts, of course).
- When the engine is started and cold, the cadillac valve takes hydraulic fluid pressure from the power steering pump and uses it to disengage the clutch so that the fan is effectively free-wheeling (NOT stopped)
- When the engine gets warm enough (based on coolant temp), the time-delay module cuts power to the cadillac valve, which relieves the pressure on the clutch, allowing it to re-engage the fan
- As the engine temp fluctuates up and down, the cycle of clutch engaged/disengaged continues as needed to keep the coolant below about 215 degrees F.

What signals the TDM to interrupt or supply power to the cadillac valve? Is it the the same sensor that provides signal to the coolant temp gauge?

 

[nspctr1]

I fired up the HMMWV this afternoon, unplugged the power cord from the cadillac valve and the fan didn't move forward/backward. I guess I need to try and free it with air. How big of a mess does this make with the lines full of fluid? What is the optimal location to blow the air into the system from. Do I need to purge the air from the system after doing this? Is there a specific part/tool I can use to make this easier/less messy? Can you spray lube in this location to prevent it from freezing up again? If so, Where do you spray it? If you have a pic of the location to blow air into this system please post.

Thx

 

[85 USMC M998]

Please don't take this the wrong way, I am not trying to sound like a jerk. But have you looked at the TM's I cannot remember where they are posted on this site but you can find them here: https://real4wd.com/manual/ among other places. The Military spent a lot of our tax dollars on the manuals and they include step by step troubleshooting. Look at Service Vol. 1 page 2-155 that is where the engine cooling troubleshooting starts.
Now to answer your question, no the coolant gauge sensor is different and in a different location and is not tied to the fan sensor.
When my fan failed on I found that the TM provide me the information needed to identify that I had a bad temp sensor and time delay module.
I also made up a Compressed air hose adapter to rotate the fan so I could remove and service the fan clutch. I recall I never had a big mess and never had to bleed air from the system. Hope this helps.

 

[nspctr1]

Didn't take it the wrong way. Just that being new to HMMWV's and trying to understand some of the new terms, parts etc is going to take me a while. Whereas, I can ask questions here and some helpful guys will even post pics to help along with ID of the part or provide alternative methods for testing etc.