65 L79

[brumbach]

What is the correct operating temperature for the L79? Mine runs a little cool, around 140 degrees. Shouldn't it be closer to 180?

 

[JohnZ]

Yup, should run at about 180* with a 180* thermostat. Shoot the upper radiator hose just above the thermostat housing with an I.R. gun and compare that against the gauge reading so you know what the gauge is really telling you - the gauges are notoriously inaccurate, especially if the original sending unit has been replaced.

A correctly-functioning thermostat won't allow the engine to operate much below the thermostat's rating; that's what they do - they determine the MINIMUM operating temperature.

 

[Rowdy1]

John............

Is there any one particular replacement sending unit that is the closest to original?

Thanks

 

[brumbach]

Yup, should run at about 180* with a 180* thermostat. Shoot the upper radiator hose just above the thermostat housing with an I.R. gun and compare that against the gauge reading so you know what the gauge is really telling you - the gauges are notoriously inaccurate, especially if the original sending unit has been replaced.

A correctly-functioning thermostat won't allow the engine to operate much below the thermostat's rating; that's what they do - they determine the MINIMUM operating temperature.

I hadn't received your response before I purchased a stat from advance auto. The one I bought is 195 degree. They said it was correct for the car but I trust your opinion more, obviously. Anyway, I installed it and could tell an immediate difference. Outside temp is 43. The car went into fast idle as it's suppose to and the temp gauge began climbing shortly there after. The gauge rose to just over 180. Pumped the accelerator, idle dropped to 750 and went for a quick run. When driving, cruising at about 45 mph, temp gauge dropped to 140. After returning home let the car idle for about five minutes and the gauge rose to just under 160. As you said the sending unit or gauge may not be correct so I'll look into an IR gun to make sure everything is good. It's definitely running warmer and for winter ops, that's what I want. Thanks --

 

[Vetsvette2002]

Yup, should run at about 180* with a 180* thermostat. Shoot the upper radiator hose just above the thermostat housing with an I.R. gun and compare that against the gauge reading so you know what the gauge is really telling you - the gauges are notoriously inaccurate, especially if the original sending unit has been replaced.

A correctly-functioning thermostat won't allow the engine to operate much below the thermostat's rating; that's what they do - they determine the MINIMUM operating temperature.

John,
Should the IR gun be pointed at the hose or at the T-Stat housing metal?
Don

 

[JohnZ]

John,
Should the IR gun be pointed at the hose or at the T-Stat housing metal?
Don

The hose is better, as it's a matte surface; shiny/reflective surfaces can cause inaccurate IR gun readings.

 

[JohnZ]

Is there any one particular replacement sending unit that is the closest to original?

Thanks

Some folks have reported good results with the Wells TU-5 (AutoZone) or the Standard ST-6 senders, some have not; it's a crapshoot. That's why an I.R. gun shot is a good idea, so regardless what sender you have, you'll know what the gauge is really telling you from then on.