Coolant temp sensor

[Wietse]

Hey guys,

I have a '69 Coronet 440, temperature meter is always showing very low.
I've checked the engine with a infrared gun and find the cilinder heads are around 180* F.
But the temp sensor of the car barely shows 120* F, my additional installed temperature gauge (VDO) shows 104* F.

After installing a new temperature sensor (and the additional VDO sensor) i noticed there are 2 sensors from original.
There was one installed on top of the water pump and that is where i installed both new sensors on a Tee piece.
The other sensor sits on the front of the pump housing and is accesible through a hole from the alternator bracket.
Do these sensors both measure the same coolant?
Or shows one the cooled inlet water and the other the hot outlet from the engine?
If so i guess i need to change the position of the sensor to get a proper reading.
Running a "cold" engine is not really good so just want to make sure there is a good water temperature supplied to the engine.

Any thoughts?

 

[oldbee]

The original location is housing behind alt.bracket. Could be bad or ur gauge.

 

[Wietse]

Sensor is new, also have a new OER temp gauge and new wiring harness.
So all that should be good, just wondering if the 2 locations measure the same water flow, or that they measure the engine block inlet and outlet temperature separate.
Behind the alternator bracket sits an old sensor, which does not work as i tried it, but before draining coolant and all that i thought better ask first if it is worth the effort and get a good reading.

 

[Yatzee]

Hey guys,

I have a '69 Coronet 440, temperature meter is always showing very low.
I've checked the engine with a infrared gun and find the cilinder heads are around 180* F.
But the temp sensor of the car barely shows 120* F, my additional installed temperature gauge (VDO) shows 104* F.

After installing a new temperature sensor (and the additional VDO sensor) i noticed there are 2 sensors from original.
There was one installed on top of the water pump and that is where i installed both new sensors on a Tee piece.
The other sensor sits on the front of the pump housing and is accesible through a hole from the alternator bracket.
Do these sensors both measure the same coolant?
Or shows one the cooled inlet water and the other the hot outlet from the engine?
If so i guess i need to change the position of the sensor to get a proper reading.
Running a "cold" engine is not really good so just want to make sure there is a good water temperature supplied to the engine.

Any thoughts?

If their not in the actual water flow path the readings will be erronius. If their in the return passage the same applies. If their in a "dead end" fitting like a branch tee they won't read right. The bulb of the sensor needs to be in the coolant flow, prior to the thermstat in a discharge passage. Gauge resistance and sensor resistance must match.

 

[Wietse]

The question is, are both locations measuring on the same side of the coolant system.
I have a suspicion that the sensor behind the alternator bracket measures the "hot" coolant from the engine and the one on top measures the "cool" side of the system that is returned to the engine after the radiator.

 

[oldbee]

The question is, are both locations measuring on the same side of the coolant system.
I have a suspicion that the sensor behind the alternator bracket measures the "hot" coolant from the engine and the one on top measures the "cool" side of the system that is returned to the engine after the radiator.

I think you're correct, I'd go with the sensor behind bracket; that's where they all were located.

 

[PurpleBeeper]

Yes, sensor behind alternator bracket is the correct location. Use your IR heat gun on the thermostat housing at motor side of the upper radiator hose. If the gages read low then "maybe" you have a poor ground....maybe clean the threads where the sensor screws in. Anything you screw into a "T" will read low.

 

[Wietse]

I will put the original sensor behind the alt bracket and keep the VDO sensor on the current location.
So i can see water temp coming out and going in!
Another plus is i can ditch the Tee and put the sensor how it supposed to be.
So far seen installing it like that did not make much difference because checking the temp on the gauge and compare with the IR gun it matches.
The coolant inside and the metal fittings get just as hot as the rest of that section so it's not like it gives a false reading.
But anyway, less connection and components...the less chance of leaks

 

[MoparLeo]

Use your IR gun to check the coolant flow in the radiator and at the inlet and outlet radiator hoses. Check the top and bottom parts of the core for temp change. This can diagnose any blockage in the core. The cylinder head temperature should be the highest of any part of the engine.