t-stat or something else?

Magus2727

New member
So my jeep regardless of the weather outside only gets up to 160F (per my dash gauge) and only under heavy use does it ever only get to the 210. Does this sound like the t-stat might be stuck open? Or perhaps the fan clutch going bad and is stuck on the "high speed" setting?
 

Tim_MN

Freakish Hand Strength
NAXJA Member
Test your temps with a touch-less Infrared Thermometer.

Replace thermostat if needed. If the thermostat works correctly, the fan cannot over-cool the engine,
 

joe_peters

New member
Test your temps with a touch-less Infrared Thermometer.

Replace thermostat if needed. If the thermostat works correctly, the fan cannot over-cool the engine,
Absolutely correct.

The standard OEM thermostat is 195 degrees--that is the temperature the coolant must reach FOR THE THERMOSTAT TO BEGIN OPENING.

The AIR FLOW through the radiator and against the bi-metal spring has to be in the 170 degree range for the spring TO BEGIN OPENING THE CLUTCH FLUID RESERVOIR. When the air passing through the radiator and hitting the fan clutch bi-metal spring is 170 degrees the engine coolant is at least 30 degrees hotter, usually more in a stock system.

Water boils at 212 degrees. Add in engine coolant and that raises the boiling point. Pressurizing the system increases the boiling point even further.
 

Magus2727

New member
Don't have a touch less thermostat. However I do have a thermocouple and a volt meter. What would I measure look at to see the temp? The outside of the housing that the t-stat is in?
 

heshhash

New member
my 89 is the same way, runs at 160 unless under a load, then it will hit 210, thermostat opens, i get a burp of heat and the temp drops to 160 again...
 

Magus2727

New member
Do the non OBD 2 controlled have a open loop and closed loop fuel curve that it followed? Will staying at 160 cause any issue with fuel economy? Or will the heat output from the heater core just not heat the cabin as fast?
 

Shorty

Gone but not forgotten...
fuel demand is determined by engine coolant temp and air charge temp (among other variables) -- cold engine will net higher fuel consumption.
 

sandsgg

New member
I think that's the big reason my mileage sux, i don't even jab an aux fan on my mj and it stays cold
 

Ecomike

NAXJA# 2091
NAXJA Member
Do the non OBD 2 controlled have a open loop and closed loop fuel curve that it followed? Will staying at 160 cause any issue with fuel economy?
Yes and yes. A good T-stat and good working electric heater in the O2 sensor are critical to getting max fuel economy in the winter.
 

Magus2727

New member
Put the thermal couple on the aluminum housing (used duct tape to secure it) after a 45 min drive home and let the car idle for about 10 min after putting the temp sensor on. I measured 178-179 degrees. Assuming a few degree difference... puts me around 185? Should be more like 210 right? So going to replace the t-stat this weekend.
 

Magus2727

New member
Replaced the T-stat with factory 195 thermostat. Did I a quick drive 2mile one way to get gas. And the temp now got up to the 210 per the gauge but then would drop down to about 170 ish or so. Of would then work its way back up. Is this normal? Guessing the motor was not fully warmed up so the t-stat was opening and closing as it reached steady state. So is this normal?
 
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