water temp issue

[jacksauto]

my water temp when warmed up would got to 180 then back down to 160 once the thermostat would open,I checked the level and found it to be low on water by about 1 gallon maybe less .so I topped it off and now the temp only gets to 130 ,shouldn't it get to a higher level ,wondering if the thermostat is stuck open,why am I getting such a low reading? puzzled!!!!any ideas out there.thanks jack

[ZGjethro]

They are cold blooded vehicles. My guess is your cooling system is working better now that you have the right amount of coolant in it.

I have been wondering if anyone is running modern temp gauges on their trucks. I have one sending unit which pegs my gauge, and another NOS one which barely register any heat. I am not sure I trust my gauge and sending units.

[8543bob]

GOOD MORNING, I installed a 160 thermo in my M, also installed a mechanical temp unit the same time. The truck runs at 160. I would Put a mechanical unit in or test it with a non contact thermometer. The not contact thermometer are cheap at harbor freight, they are a great tool to have in your bag.
BOB

[tbone1004]

agreed with Bob, use an IR thermometer on the head and block. You have to remember that when the thermostat opens you will get a slight drop in temp as the VERY large radiator capacity is now in circulation. I would put an engine block heater in there if you don't want to have to wait for it to warm up. Even my Jeep WJ with the 4.7L takes a good 4-5 miles of regular driving to get up to temperature and the M37 has another half gallon of capacity with 2 less cylinders at much lower RPMs. Combined with a significantly larger iron block and head where my Grand Cherokee has aluminum heads and a lighter block. My water temp gauge is currently nonfunctional but I also use the block heater before I fire it up to help the engine a bit. I'd put a 180 or 190 thermostat in there and just let it go. Odds are something in your sender or gauge is off and the higher temperature it runs the happier the engine is going to be.

To test the sender you can take put a multimeter on the gauge and measure resistance that way which will give you readings to which is right. You can also take the senders out and put them in boiling water to see which gauge is measuring properly *they should both obviously be reading somewhere in the 210 ish range

[jacksauto]

again you guys have great responses,it sure makes me feel a lot better knowing u guys are willing to sharte your knowledge about these beasts,cant wait for my next problem LOL..I am sure learning a lot about these trucks and might I add ...LOVING IT.....will put your info to use right away thanks Jack