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LMC 1500 running too hot what is the correct thermostat?

hansoni

Member
We have the AMC 4.0 in our machine. After running it heavy this past weekend I would say it's running too hot at 210 degrees. Finding conflicting results online, most Jeep forums say this is right, wondering if it's right in our rig.
I did find in the manual and in the list of parts it calls out a 160 degree thermostat.
Can anyone confirm this?
Steve
 
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300 H and H

Bronze Member
GOLD Site Supporter
Not sure about your 1500 specifically, but I do know lots of Gasoline fired industrial engines have 160 deg thermostats in them. Back in the day medium duty trucks had them as well. These engines see lots of high loads, and the 160 gets the coolant moving sooner, and this helps some what with temp control. It may not help your situation as radiator condition, dirt accumulation, and other things with in the cooling system all have an effect. For instance, a former owner might have had to replace a water pump, and decides the fan shroud is just a headache to get in there with the fan, due to tight clearance, and bingo suddenly this machine has a critical part no longer on the playing field... Just an example mind you...

Regards, Kirk
 

Snowtrac Nome

member formerly known as dds
GOLD Site Supporter
I will give you my 2 cents worth as a jeep owner 210 is border line to hot for a carbureted engine and way to hot if you have the plastic valve cover. you likely have a 258 engine not the 4 liter the 4 liter has a renix efi system and a shorter stroke than the 258 and I believe first saw service in Cherokees and comanchies around 1990. if you are getting to hot some one might have taken the thermostat out or the radiator is plugged also check base timing and fuel mixture these can have an effect on how hot the engine runs if yours is a carbureted 258 than you should be running around 180. and an electric fan wont work as well as the belt drive fan been there already.
 

hansoni

Member
Thanks guys, I am planning on changing over to a 180 thermostat and flushing the system. Our engine has a aluminum valve cover. It is also missing the shroud. Got a shroud coming from Summit should help. Some guys on the Jeep forums talk about 210 is normal any less may not run right, we'll see.
 

Snowtrac Nome

member formerly known as dds
GOLD Site Supporter
also check which way the fan is blowing I have seen industrial engines with reverse fans which with a front mounted radiator would limit the amount of air going through the radiator
 

Snowtrac Nome

member formerly known as dds
GOLD Site Supporter
food for thought that 258 amc 6 is like a ford 300 6 with 7 mains but they also weigh a lot more than a small block chevy v-8
 
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