Temperature Gauge question

[Thumper580]

1986 M998, original gauges....
Radiator flushed, new thermostat.
Temperature gauge never went above 160 deg. on the gauge. Cooling fan would engage on warm days.
Replaced the gauge, but still not above 160.
Replaced the temp sending unit, now it goes up to about 215-220 and stays in that range, so I assume the sender was the problem.
The cooling fan has not kicked in however the weather is cool here now @ 45-50 deg.

My question is this seems too high of a temperature reading on the gauge...... I can assume everything is fine and the new reading is due to gauge inaccuracy. Haven't changed anything else.

Thoughts????????

 

[Action]

Put the old gauge back in and see what it reads.

 

[Thumper580]

Put the old gauge back in and see what it reads.

I was sitting here thinking about doing that tomorrow.... To eliminate that variable. Thanks.

 

[Daves86]

And Check your grounds!

 

[Thumper580]

And Check your grounds!

I will...and I also installed one of the additional grounding assemblies.

 

[Thumper580]

Update...
Put the old gauge in and it reads the same as the new gauge, so it wasn't broken. The sending unit made the difference.
Still reads about 220 on both gauges while driving.
I got my infrared gun and shot the thermostat housing after my test drive and still running.
The aluminum housing read about 183F.... I know there is a slight loss through the housing but not much.
I've tested the infrared gun and it's only about 1.5F off of a good test source.
So, I guess 220F on the gauge is my new "normal" 185-190F actual temperature......

 

[Thumper580]

One more thing.... I did put some pipe dope on the threads...... Was that a bad idea???

 

[DREDnot]

I just installed a few sets of gauge and sender and fan switch and thermostat.
Running some road tests today to verify fan engagement cycles and burnishing the rusty/dusty brake rotors.
78 degrees outside.
Kinda daring the trucks to overheat.
New gauges performed identically. Came alive promptly and would hang around 190 idling then while driving would head up to 225ish and the fan would kick on for maybe two minutes and the gauges would lag showing the amount of cooldown to maybe 210 and basically cycle back and forth to either side of the 220 hash mark.
Shot it with my HF temp gun and was consistently close in the water pump/thermostat area than the gauge was reading at the head.
This was the hottest spot I could find that wasnt exhaust related.
One truck was turbo and the other was N/A and both performed identically

Sounds like you are reading more correctly/realistically now.
At least with the replacement parts commonly available in these unprecedented times.

This has been my vaguely scientific experience with about five of these temperature control/monitoring sets.

Any thoughts from others on their observations of these aftermarket gauge parts?
Similar? different?

The temperature that these thing seem to run at gives me anxiety

 

[DREDnot]

One more thing.... I did put some pipe dope on the threads...... Was that a bad idea???

Pipe dope is the way to go for the temp sender.

It allows the threads to make metal to metal contact that a one wire sender needs to ground properly. The liquid pipe sealer fills in the voids in the threads sealing the assembly.

Teflon tape more often than not will act as an insulator even with one or two neat wraps. Not an issue with something like the fan switch though. It has two wires...in and out...and doesnt have to rely on grounding through the housing

 

[911joeblow]

Guys, these temperatures are all normal. Remember that these diesels need heat to achieve full burn of the air/diesel mixture. Dont fight to drop the overall system temps. That being said though these engines have a LONG history of overheating at the back of the blocks around cylinders #7 and #8. The rear overheating issues cause head gasket failures, cracked heads and scored cylinders. Consider a balance upgrade kit for your cooling system to fix that issue.

Military HMMWV, HUMVEE Cooling Upgrade System

PARADOX HMMWV 6.2/6.5/6.5T COOLING UPGRADE KIT (patent pending)This is simply the best bang for the buck upgrade you can make to your truck, period! Must do before any performance or horsepower mods.All HMMWV HUMVEE trucks with GM Detroit Diesel V8 6.2/6.5/6.5T engines all share an inherent...

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[Action]

Guys, these temperatures are all normal. Remember that these diesels need heat to achieve full burn of the air/diesel mixture. Dont fight to drop the overall system temps. That being said though these engines have a LONG history of overheating at the back of the blocks around cylinders #7 and #8. The rear overheating issues cause head gasket failures, cracked heads and scored cylinders. Consider a balance upgrade kit for your cooling system to fix that issue.

Military HMMWV, HUMVEE Cooling Upgrade System

PARADOX HMMWV 6.2/6.5/6.5T COOLING UPGRADE KIT (patent pending)This is simply the best bang for the buck upgrade you can make to your truck, period! Must do before any performance or horsepower mods.All HMMWV HUMVEE trucks with GM Detroit Diesel V8 6.2/6.5/6.5T engines all share an inherent...

paradoxbydesign.com

here we go again...,

 

[springer1981]

All I can add is I have recently updated my temp gauge to a newer style and with it I had to replace the sending unit because they are different. They look the same but function differently. Make sure you have the correct sending unit for the gauge. I don't know how to tell the difference because I didn't look when I had them out.

 

[86humv]

All I can add is I have recently updated my temp gauge to a newer style and with it I had to replace the sending unit because they are different. They look the same but function differently. Make sure you have the correct sending unit for the gauge. I don't know how to tell the difference because I didn't look when I had them out.

Black rubber boot unit is for all gages, except gage with light inside...its the latest and takes the sending unit with a grey boot.

 

[springer1981]

Black rubber boot unit is for all gages, except gage with light inside...its the latest and takes the sending unit with a grey boot.

Interesting because I just bought the one with the light and it came with a sending unit specifically for that and it had a black rubber "boot" that I assume in the connector the wire plugs into.

I guess I'll have to double check it ... Just looked it up online and the picture shows a gray boot.

 

[Milcommoguy]

It has been said that the turbo 6.5l run a little higher ??? With all the variables... Stuck fans, rust and crud, leaves, bent up fins, poor or little repairs, maintenance.... clearly the cooling system should be on the list.

YES, gauges and senders not the most accurate. Got to believe in something when one gets a good set paired up.

I have the 6.2L and went thru all the in's and out's with my rig. At first never could get the temp above 180. That went on for a week. Time to dig in. Stuck fan clutch, fixed that, Now it was running high 220 and holding. Jacked up Cadillac valve. Replaced. Now cycling but running high than published temps and cycle times, more on than off.

Best thing I did was and for the years of unknown service... flush and flushed. Ran it around a week with chemicals and 2X flushed again. While a bit messy and pain in the butt, cheap insurance... it now cycles like a champ. 50/50 mix on the antifreeze, system pressure test 16 PSI and holding. Desert DOG rig. Hell hot in summer, freeze in winter.

My normal "Cruisin along in my 86" switch opens at 220 +/- and on comes the fan. (open is ON) A minute or two, later and temp slowly coming down to just above 190. Engine loading and outside temperature, back up it goes... and the cycle repeats. Lots of hysteresis with time, loading and temperatures. When switch hits the mark it works. Riding along. after some time, back up to the 220 range... repeat cycle. Make sure your switch is of quality. Best is this one by REM Industries. The blue metal tag is the one for me, IMO.



Sure all the trucks have there own personally. "Woo Nellybelle" I call it the "heart beat " of the HumV cooling system. If one is paying attention to operation you know what I say. I even went to the trouble of adding a cool LED. LED on, for the COOL OK nerdy.



WAIT BRAKE COOL LAUNCH

It's just another "thang" to stay on top of Humv, CAMO

Again... TM's your BESTest friend. "86humv" OK TOO.

 

[Action]

The -387-10 manual lists 185 - 250 normal operating temp for the 6.5 turbo. I havent seenone get to that temp, though. The newer guages do not get to the red until 250.

 

[Action]

280-10 shows n/a at 190 - 230 degrees normal operating temp.