First things fist.....
you would know if the fan clutch is working cuz when it kicks in you will hear and feel the loss of power.
********While driving, i can hear what i assume is the fan clutch engaging once it gets to 240. I know i hear a high pitched squeek then everything gets really loud and there is some power loss. I had hoped to check it, but while it's stationary it doesn't seem to get hot enough to kick on the fan for me to see. Before, i was convinced it was working at it was spinning when the engine was on, but i guess thats just it free wheeling.
with engine running cold...unplug the TDM wire...it's the plug with 2 wires not the one with 4.
the fan should move in and out....it fails in the engaged mode, the fan spins regardless, its just then when the fan clutch is engaged it is not free wheeling and its moving air. Also, I find them engaged on most customer trucks...even when everything is working, you need to take a dead blow mallet and whack the crap out of the fan clutch housing...the clutch plates get stuck...I do this on brand new NOS units out of the box...I apply 100psi of air and they won't move in and out till I unstuck them.
*******Ok so then fan will move towards and away from the engine when i unplug the tdm wire? I will check tomorrow morning and see. Thank you.
2nd, change the thermostat....most are marked which way they go...you need to get one that opens at 180 degrees, order it from kascar.
********this is the one thing that i had planned on doing anyways so i was way ahead of you. I figured that even if it wasn't the issue, eventually the thermostat would go bad and i'd have a back up. I called Kascar as i wanted to make sure i had the right part. The guy i talked to told me i didn't need one as HMMWV's run really hot and as long as i wasn't having cylinders shutting down or coolant blowing out everywhere then i should be ok. He cautioned that i should check my radiator by holding a flashlight behind it and seeing if it's clogged. I explained that the radiator was "NOS" and that the temp gauge reads 240 before it cools down to 220. He still said that was normal. My reply was, "if normal is on the far end of the gauge, then how do you know when things are abnormal?" He reassured me i didn't need to buy anything, so i didn't. Do you have a part number for the 6.5 from Kascar? I'll order it tomorrow and send you one as well for your help. PM me your address.
3rd, how's the coolant
**********Coolant looks fine. It's at the cold fill line and doesn't look discolored.
4th, you say the motors new? Rebuilt? New? Seen plenty of New motors that are painted junk...cost one of my customers 3k for the bad motor and 6k for a new motor.
***********It was a NOS motor that was inside one of those plastic crates.
5th' your radiator...is it new? The hmmwv radiator is a PITA, I get them rodded but more then half the time they are toast, remember, they are 28yrs old.
***********Radiator is NOS as well, i'm sure that doesn't mean that i couldn't have rust on the inside while looking all shiny black on the outside after sitting in a damp .Gov storeroom. The coolant doesn't appear to be rusty colored though.
6th, 240 IS NOT NORMAL...Nor is 220, all my trucks...and I have quite a few, plus all my customer trucks I work on and drive, run at 200 with the fan clutch coming on at about 215 which will take it back down to 200 quickly.
it is going to run hotter opinion town then on the open road, you will notice the Fan clutch coming on frequently, it will startle you at times....it's that load at higher speeds.
*********It certainly is startling and hard to talk during it's cycle. I figured 240 wasn't normal. I keep getting told otherwise by folks and i can't wrap my head around a gauge that is set up to tell you that everything is good-normal, but not tell you when something has gone awry. That being said, i even find it odd that they don't read normal as dead center for people with "normal" operating temperatures.
7th, your gauge is bad....use a thermometer in the overflow tank to see the real temp.
********That is what i am hoping for most of all, I will employ disconnecting the TDM to check that as well as temp checking the coolant. Work got a little busy for me today and i didn't get the opportunity to do anything. Will the overflow tank provide an accurate reading?
Hope this helps....call me if you need any help.