engine temperature gauge not working...

[RamTrac1990]

So I recently changed my thermostat housing and all the parts to it, but for a few days now my gauge reads on C and barely ever gets above the line. It never reaches the middle. I changed the sensor as well so I don't think that's it. Does anyone know what it could be?

 

[RamTrac1990]

It's a 2004 Sport Trac if that matters

 

[2000StreetRod]

new thermostat?

Did you install a new thermostat when you replaced the housing? Did you fill the block with coolant up to the thermostat level before installing the top cover? Do you have a failsafe thermostat?

If you didn't prefill the block with coolant than the engine can overheat until the air gets out of the system. A failsafe thermostat will stick open when it's upper temperature limit is exceeded. Does the temperature gauge move at all?

Do you have the ability to read the engine coolant temperature via the OBD-II port?

 

[RamTrac1990]

Yes I replaced the thermostat I installed a failsafe one. I didn't fill the block with coolant until after it was installed. And the needle moves just barely but not much at all.

 

[2000StreetRod]

stuck open thermostat?

If the thermostat is stuck open and you're located in Colorado Springs the weather there may be cold enough that the engine coolant only slightly warms up. My 2000 SOHC V6 has a temperature sender for the instrument cluster gauge and an engine coolant temperature sensor for the PCM. I think the 4th generation Explorers have only one sensor. I don't know about your Sporttrac. If the sender was disconnected the indicator on the instrument panel wouldn't change after the engine is started. If the engine cold starts and idles normally then the sensor for the PCM is proabably functional.

Do you have any diagnostic trouble codes?
Do you have access to a scanner to read the PCM reported engine coolant temperature?

 

[RamTrac1990]

I didn't have any codes popping up when I took it to auto zone to be looked at but my check engine sign came up but they told me to disconnect the battery and it should go away but so far it came back up again

 

[2000StreetRod]

multiple occurrences

For non-critical engine/transmission faults the PCM requires multiple occurrences (more than one engine start/drive cycle) before illuminating the check engine light. Clearing the codes doesn't fix the fault - it just eliminates the light for a few engine start/drive cycles. The codes are usually helpful to diagnose the fault. What were/are the code(s)?

 

[RamTrac1990]

If I remember correctly it was an lean 1 and 2 I think

 

[2000StreetRod]

unrelated codes

If I remember correctly it was an lean 1 and 2 I think

Those codes are unrelated to your engine temperature.

 

[RamTrac1990]

Yea that's what I was told but I don't have a clue as to what it could be with the the gauge. Is there another sensor that needs to be replaced when it come to the engine temp gauge or is just the one on top of the thermostat housing?

 

[2000StreetRod]

one or two sensors?

As I stated previously my engine has two sensors.

One is the engine coolant temperature sensor to the PCM and the other is the engine coolant temperature sender to the analog instrument cluster. They are not interchangeable. They have different connector keying.

I know that the recent Mustang SOHC V6 only has one sensor in the thermostat housing. It sends data to the PCM and the PCM sends data to the digital instrument cluster. I've been waiting for the aftermarket all metal housing for my configuration to be available. It's been available for the Mustang configuration for several months. If you only have one sensor on the housing then you have the Mustang configuration.

Do you have any symptoms indicating the thermostat is stuck open vs the sensor is defective?

 

[RamTrac1990]

Not to my knowledge unless I open it up and look

 

[RamTrac1990]

This is the old housing along with the old sensor. As you can see I only have one plug to insert a sensor the other plug isn't even opened.

 

[2000StreetRod]

same as Mustang

That's the same as the Mustang unit. If the sensor isn't functional and always reads cold then the mixture should be rich for warm start. If the sensor is functional and the thermostat is stuck open then the mixture should always be correct. Do you get heat out of the heater after driving for five minutes. If not, then the thermostat is probably stuck open.

 

[RamTrac1990]

It's lukewarm heat even after driving for about 30 miss it only gets warm never hot.

 

[2000StreetRod]

bad thermostat

It's lukewarm heat even after driving for about 30 miss it only gets warm never hot.

The thermostat is bad or you installed it incorrectly.

 

[RamTrac1990]

I'll take a look at it then when I get a chance tomorrow thanks ill attempt to put it right or even figure out if it's bad

 

[RamTrac1990]

Ok so I finally got around to checking it out...and the dawned failsafe thermostat was defective! Put my original one in and now I'm sitting at the right temp gauge along with nice super hot air to be able to survive the Colorado winter coming up. Thanks for all your help I appreciate it StreetRod!!

 

[2000StreetRod]

prefilling the block

When the block is not prefilled with coolant it typically overheats at first engine start up. The fail safe thermostat overheats and fails open. It probably wasn't defective. I'm glad it's running normal now.