1991 HMMWV overheating

osteo16

Active member
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Location
Evansville, IN
Can't say for sure... I don't think it's out of your league. You're just on first base and heading to second. Big hitter on the bench here. Just be clear on sending the correct signs. (symptoms) Can't get home without runing the bases in order while playing smart and hard.

Watch out for less than top quality parts. Good way to get put out. OUCH

Check the play book (TM) to clear the possibility of grounding out and not seeing the gauges or anything working right. Really want to have them property grounded. Easy to execute before spending money.

When was the last time the waterboy check the cooler. That stuff could be nasty. Auh !

Lots going on here. We understand the need for a designated runner too.

Up in the peanut gallery rooting for team SS, and bmdupont, CAMO
Out of his league??? Had HMMWV for 5 years and not sure how anything works... Wow.. Radiator fluid.....That would be COOLANT.. Must be an Oregon thing. Id say you best pay VERY CLOSE attention to everything that is in this post.. YOU will need it.. Test your sensors, make sure your RADIATOR FLUID (coolant) is at the Correct level. And LEARN about your vehicle..We don't need another non educated person causing public issues that could hurt our hobby and further impair our ability to keep our rigs on the road. Next thing you know, your wheel falls off because you haven't checked your hubs and someone gets killed.. Please be a responsible owner.. Cmon Man

Sorry if I hurt any feelings... Rough day... Good Luck..
 

TOBASH

Father, Surgeon, Cantankerous Grouch
Steel Soldiers Supporter
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These are not the vehicle to not understa
Appreciate the replies, had the truck for 5 years. My first guess is the temp sensor.

Just thought it was an interesting coincidence the gauge just stopped working this spring and this happened.

I lack understanding of how the temp sensor, gauge and fan are connected or aren’t connected. I read some older posts about other users with over heating issues and still did not understand If there was a connection between gauge and fan. Does not sound like they are based on replies.

My first step will be to clean the gauge connections, have had this problem before with other things not working due to bad connections and dust.

Have a new temp sensor, gasket and radiator cap on order. Then it will be replacing the sending unit. If it goes beyond that I will have to take it to someone as it’s out of my league.


Sent from my iPhone using Tapatalk

A temp sensor WILL NOT cause overheating!!!!

Low radiator fluid, clogged radiator, bad radiator hose that got soft and collapses under use, bad thermostat (NOT TEMP SENSOR), bad fan clutch, driving too fast will all cause overheating.

Learn your vehicle or sell it and buy a car under warranty.

Best,

T
 

MattNC

Member
91
25
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Location
Raleigh, NC
You guys are a tough crowd! I wanted to share what I've learned with him as I only learned by asking a lot of stupid questions to patient people and reading info I was pointed toward. I give him credit for wanting to learn. It could be way worse, he could be that whistlindiesel guy on youtube and filling the bed with cement and running it off a cliff!
 

GMVguy

Member
179
6
18
Location
Utah
My 6.5 got hot today because the fan did not engage over 220. The Cadillac valve verifies good (properly engages fan clutch when unplugged from harness), but the Thermostatic Switch has no effect on fan clutch, whether plugged in or unplugged. Does that confirm that the thermostatic switch is bad? Also, shorting the A & B wires on the harness also does not effect the fan clutch.
 

TOBASH

Father, Surgeon, Cantankerous Grouch
Steel Soldiers Supporter
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Location
Brooklyn, NY
I think I've had enough of the Cadillac valve and I will be converting my system to a traditional GM clutch.

I don't ford water and I have no need for a fan clutch. The HP loss can't be greater than 1%, and honestly, the idea of a thousand dollar system to control an engine fan that can also dump all my power steering/power braking fluid when it fails is stupid.

IMHO
 

Bulldogger

Well-known member
Steel Soldiers Supporter
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Location
Woodbridge VA
I think I've had enough of the Cadillac valve and I will be converting my system to a traditional GM clutch.

I don't ford water and I have no need for a fan clutch. The HP loss can't be greater than 1%, and honestly, the idea of a thousand dollar system to control an engine fan that can also dump all my power steering/power braking fluid when it fails is stupid.

IMHO
I've had similar thoughts, either a rubber balded fan or electric. The fan system is mentioned far too many times on this Site as a point of failure and we've all had to work on ours, or so it seems. Glad mine still works!
BDGR
 

GMVguy

Member
179
6
18
Location
Utah
Had a similar issue yesterday.... Thankfully I was watching the gauge when the truck went over 220 and fan did NOT kick on, so some coolant started boiling over and I pulled over to let it cool. Unplugging the Cadillac valve and the TDM causes the fan to engage properly to cool the engine, so that was the temporary fix to drive home.

My first thought is the Thermostatic switch (12338596) is bad, so with the engine running, I disconnected it from wires 458 A & B and the fan clutch did NOT engage. I jumped the two wires from the harness (458 A&B) to imitate an activated thermostatic switch, and the fan again did NOT engage. That has me thinking the Thermostatic switch might be doing its job but something else isn't? Where would you start?
 
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