Deuce overheating help.

[Beerslayer]

The oem gauges are usually very accurate. Check your sending unit, wiring and get a new military one.

That looks like an easy test, I will give it a try. Thanks!

 

[Rolling_Eudaimonia]

Have you tried to flush out the engine block??? Even with all the fun stuff you've put on the engine if the flow in the block has some flow constriction it will overheat and even cause excessive wear on the waterpump. I would take off everything and try to see if the block itself is actually circulating the coolant properly... then I would look to the water pump and then the new coolant filter and finally get a priest.

 

[Beerslayer]

Have you tried to flush out the engine block???

Thanks for the suggestion. I had the radiator shop flush out the block too.

Now I have gone from one extreme to the other. The temp guage is reading 240 but with the trusty Harbor Freight IR temperature checking thing, the motor is actually running around 160. I suspect the new thermostat might be stuck open as after running the truck hard with a two ton load, pump turned up, hard pulls, stop for a bit and it is staying at 160 or so depending on where you measure it.

Can that tight fitting thermostat seal prevent the thermostat from closing?

Bought a new temp guage, got a SW mechanical unit.

 

[cranetruck]

A reading of 240°F is full deflection on the temp gauge, which would indicate that the connection to the sending unit is shorted to ground.

An engine temp of 160 is pretty normal under a lot of driving conditions in a cooler climate. When you installed the T-stat, it was closed and unless you observed the temp going above 180-185, it has yet to open.

I have a permanent radiator cover installed to keep the temp up. It was removed only when hauling the 8x8 from OK to VA and when pulling the 9,000 lb laundry trailer through the Rockies a couple of years ago. Even then, the temp stayed below 195 degs ( I use a digital thermometer to monitor the engine temperature in some situations and it agrees very well with the dash gauge).

Edit: Added image

 

[Beerslayer]

Thanks for the pictures Bjorn!

Tested the sender. I assigned it to my Chief Nerdy Computer Technician as a Science Project. He loved it! He was all in the kitchen with multimeter, boiling water, a candy thermometer, and an IR temp guage to verify.

The sender wasn't shorted but was WAY OFF. There was a linear progression as it heated up, which was what had me fooled, but it was so far off as to be completely whacked.

I installed a Stewart Warner mechanical gauge today. After a 45 minute warmup the temperature was barely over 100. Took her for a drive with the radiator half blocked with cardboard and the temperature finally got up to 175. Don't think the thermostat ever opened.

At least now I know it isn't heating and does get up to a reasonable temperature.

Thanks everyone for all the help with this, I really appreciate it.

Overheating Case Closed!

 

[bigtruck]

Cranetruck,

From which manual are you pulling these troubleshooting illustrations...? I haven't noticed these in the basic TM 9-2320-361-20.. Please advise. Thanks

 

[cranetruck]

They are in my xm757 TMs (TM 9-2320-230-20), but the M809 TM 9-2320-260-20 has some very similar illustrations. The xm757 has the multifuel engine like the deuce, so much the same applies...

Edit: Oh, the manuals are from the late sixties or early seventies and the illustrations may not be the same in newer TMs. For one thing, the old Simpson VOM is no longer used.

 

[bigtruck]

Well,,, if the conversion chart above (resistance to temp) is applicable to my deuce's LDT-465 (which seems to be the case), my temp gage is reading 50 deg F higher than it should... Which is comforting,, because i just made a 100mi trip with it reading hot (~240F)... I stopped several times to let it cool down,,, and from feeling the engine/radiator i suspected the gage or sending unit had to be malfunctioning;; however,,, it is certainly a relief to confirm this.... Plus, this conversion chart was very helpful in pinpointing the problem (gage or sensor)..

I can't find any replacement 24v temp gages (without ordering)... I could install a 12v gage and add a resistor (of the appropriate value to adjust voltage to work with the 12v gage) but such resistors with the correct power ratings are difficult to find (not available at your local radio shack);;;; so i've opted to go with a $16.99 mechanical gage from autozone....

 

[bigtruck]

FYI to all---

I installed the new mechanical temperature gage (sunpro CP8217) last night.. Gage fits the instument cluster panel hole well,, as expected,, and it was easy to snake up to the intake manifold;;; HOWEVER, i do have some words of advice to anyone who choses to use the same gage as i have--------- the original coolant sensor port is too shallow to accomodate the longer probe that this gage comes with.... The smaller bottom port is also too shallow... The port right above the heater hose outlet is just deep enough,,, so use that one and save yourself some hassle!

As for the temperature readings that i derived from my previous resistence check,,,,, they agreed perfectly with my new gage! So,,, i can personally confirm the accuracy of the conversion chart in cranetruck's previous post... Not that i questioned the chart's accuracy,, i just wasn't absolutely sure that it was applicable to the LDT.... IT IS!! (not surprising,,, i know)

Thanks cranetruck!! You saved me some time!!