1. Check the level you filled the coolant to...If you overfilled it this will happen.
2. Did you add the correctly diluted antifreeze?
3. Check to be sure the radiator is unobstructed
Either an air bubble, the thermostat or the water pump.
Air bubble (pocket) - Just because the radiator is full, doesn't mean the engine is. When an air bubble circulates through an engine it will cause the temp gauge to swing from hot (when water is in contact with the sensor) to cold ( when air is in contact). The less water, the hotter the engine. Easiest fix - add water.
Thermostat - Keeps water circulating in the engine separate from the water in the radiator until it gets to a certain temperature. At that point, it opens and allows the hot engine water and the cooler radiator water to cycle. Hot to radiator, cool to engine. As the cooler water flows over the thermostat, it closes, allowing the cycle to repeat. If it opens at the wrong temp, or not at all, your engine will overheat. Water will begin to boil. Steam will make the temp gauge swing erratically.
Water pump - If the water pump is failing (sometimes the impeller will come of the shaft), the water will not circulate. Same results.
Troubleshoot:
First and foremost: BE SAFE!!! Wear safety glasses. Start this with the engine cool. When you look in the radiator, do it from an angle and as far away as possible.
Have a hose or a couple two liter bottles full of water.
Take off the radiator cap. (Do not take off if engine is hot)
Is the water level low? If so, top it off.
Make sure the transmission is in either PARK or Neutral and set the parking brake.
Start the engine.
Observe the water level in the radiator. If it drops, top it off again.
At first it should do nothing. The water in the engine is still cool. The thermostat is closed. As the water in the engine heats up, the thermostat will begin to open. When it does, you will notice the water level begin to surge up and down.
Check your temp gauge. If the gauge getting close to the 'Red Zone', the thermostat should have begun cycling before now. Go back to the radiator and check it.
When (if) the thermostat finally opens all the way, the water will start moving as it cycles through the system. You will be able to tell the difference.
If you see the water flowing, the water pump is ok.
If the water does not start to move and the gauge is getting close to 'Red', shut the engine down and let it cool. Do not put your face near the radiator. If the thermostat suddenly let go, The hot water, driven by steam, could erupt out of the filler hole. Replace thermostat. Rerun this test. If results are the same, replace water pump.
Does the water level drop at this point (air bubble)? If so, top it off while it's circulating. Adding cold water will close the thermostat. Be prepared to wait through the cycling two or three times.
Check the temp gauge again. Has it leveled off?
When you don't need to add water any more, put the cap back on. Observe the temp gauge for a few more minutes. has it stopped the erratic behavior? If so, it was an air bubble and it's gone. If not, replace the thermostat.
Let me know how it goes. If you have any other problems, click the ASK button.
I have a 2006 and had the same problem. The car was still under warranty, so I took it in for repair. Several times. They finally replaced the thermostat and that solved the issue. Try that.
Good luck and please let me know how it works out for you.
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Without testing ,hard to say for sure . Gauge could be going bad or the engine coolant temp sensor , wiring for sensor , PCM/ECM etc..... Knowing where that info originates an how it gets to the instrument cluster gauge is key in diagnosing the problem . Having worked at GM dealer ships an having correct tools an information gives me an edge over most . Most people would just replace parts an hope it fixes it . The first place to start would be to hook up a factory or professional scan tool an check for DTC'S - diagnostic trouble codes in the instrument cluster an the PCM/ECM . View live data inputs from the coolant temp sensor to the PCM?ECM - engine computer ,also see if that same info is getting to the instrument cluster . Most usually , if the problem is happening at the time we can't find the fault .
The Coolant temp sensor is an input to the PCM , the PCM sends this if to the instrument cluster on the serial data network . Don't know if you know what that is ?
Engine Coolant Temperature Gage
The instrument panel cluster (IPC) displays the engine coolant temperature as determined by the engine control module (ECM). The IPC receives a serial data message from the ECM indicating the engine coolant temperature. The engine coolant temperature gage defaults to 100°F (40°C) or below if:
• The ECM detects a malfunction in the engine coolant temperature sensor circuit.
• The IPC detects a loss of serial data communications with the BCM.
• The BCM detects a loss of serial data communications with the ECM.
GM did have problems with stepper motors inside instrument clusters 2003 to 2006 . Stepper motors are what control the gauge needles . https://www.youtube.com/watch?v=oTm2oDx-_GM
What
diognostics say its a sensor ?????? No diagnostic's ever tell's you it's a sensor . You as a technician would need to prove that by testing electrical circuits , viewing coolant temp sensor . Hooking scan tool and trying to command the gauge with by directional control . The temp gauge not showing any temp. ? No movement ?
Engine Coolant Temperature Gage Inaccurate or InoperativeStep
Action
Yes
No
Schematic Reference: Instrument Cluster Schematics
1
Did you perform the Instrument Cluster Diagnostic System Check?
Go to Step 2
Go to Diagnostic System Check - Instrument Cluster
2
Install a scan tool.
Turn the ignition ON, with the engine OFF.
With the scan tool, perform the Lamp and Gauge Check in the IPC Special Functions list.
Does the engine coolant temperature gage move up and down when commanded?
Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems
Go to Step 3
3
Replace the IPC. Refer to Instrument Cluster Replacement .
Did you complete the replacement?
Go to Step 4
--
4
Operate the system in order to verify the repair.
Did you correct the condition?
System OK
Go to Step 2
Would hate for you to replace the coolant temp sensor an find out that's not the problem ! Does the vehicle start an run good ,trans mission shift good ? If so it's not the coolant temp sensor .
Engine Coolant Temperature Gage
The ECM sends coolant temperature as determined by the coolant temperature sensor to the BCM via CAN serial data. The IPC displays the engine coolant temperature with the gage when the BCM sends a class 2 message to the IPC indicating coolant temperature percentage. The engine coolant temperature gage defaults to cold (0°) or below if:
• The ECM detects a malfunction in the engine coolant temperature sensor circuit.
• The IPC detects a loss of class 2 communications with the BCM.
• The BCM detects a loss of CAN communications with the ECM.
Check engine light on ? The coolant temp sensor is a input to the PCM - engine computer ! All wires come from an go to the PCM . What type of problem are you having ? Maybe able to save you some aggravation an time chasing gremlins . Coolant gauge not working ?
Engine Coolant Temperature Gage
The instrument panel cluster (IPC) displays the engine coolant temperature as determined by the powertrain control module (PCM) or the engine control module (ECM). The IPC receives a serial data message from the PCM/ECM indicating the engine coolant temperature. The engine coolant temperature gage defaults to 100°F (38°C) if there is a malfunction in the engine coolant temperature sensor or the IPC detects a loss of serial data communication with the PCM/ECM.
But if you insist ,you can find free wiring diagram's here http://www.bbbind.com/free_tsb.html Enter vehicle info. year , make , model an engine ! Under system click on engine ,then under subsystem click on fuel controls . Click the search button then the blue link. The second an third diagrams both show coolant temp sensors . Both go to the PCM .
The temperature gauge sensor as you call is for more then just the temperature gauge . The temp. sensor is an input to the PCM -engine computer ! If it were bad you would have drivability problems , the transmission would not shift correctly an the check engine light would more then likely be lit .
Engine Coolant Temperature Gage
The IPC displays the engine coolant temperature as determined by the PCM. The body control module (BCM) receives a class 2 message from the PCM indicating the engine coolant temperature. The BCM converts the engine coolant temperature into a percent gage deflection. The IPC receives a message from the BCM via the serial peripheral interface (SPI) indicating the requested gage position. The engine coolant temperature gage defaults to 38?°C (100?°F) or below if:
?€¢
The PCM detects a malfunction in the engine coolant temperature sensor circuit.
?€¢
The BCM detects a loss of class 2 communications with the PCM.
?€¢
The IPC detects a loss of SPI communications with the BCM.
Your gauge is more suspect then the sensor . gm had a problem with stepper motors that control the pointer for the gauge !
the usual suspects are:
stuck shut thermostat
clogged raiator
dead water pump
low coolant level
it's sunday, rovers don't work on sunday.
Then again, maybe its wednesday, rovers take half a day then.
once the truck is fully warmed up, feel the 2 heater hoses going through the firewall in the engine compartment. they should be hot to the touch. if they are, then the problem is most likely the heater controls, such as the temp. switch on the dash or the blend door itself inside the dash. if they are cool, check that the coolant is completely full. just because the temp gauge reads normal doesn't mean there's enough coolant in the system to fill the heater core. remove the radiator cap once cooled and top off if needed. if it is, or was, low, its possible to get air the the cooling system and block flow of coolant to heater core.
CHECK GAGES light (1) indicates a potential engine failure(low oil pressure, low coolant, coolant overheating) has occurred. · Check gages and shut down engine. Gages should read as follows: Oil pressure 5 to 10 psi (34 to 69 kPa) at idle; Water Temp gage below 230 degrees (110 C).
· Check engine oil level (Para 2-11) if OIL PRESS gage indicates low reading. Check coolant level (Para 2-11) if Water Temp gage indicates high reading. Notify Unit Maintenance if levels are low.
If CHECK ENGINE light (2) is on, check engine oil pressure gage (3) and water temperature gage (4). If both indicate normal, proceed with mission and then notify Unit Maintenance. If either one does not indicate normal, stop engine immediately and notify Unit Maintenance
The needle on the dash gage can be pulled off and slipped back onto the stem of the gage. First get an accurate temp gage to be sure what the engine temp is operating at. Then remove the face of the dash gages and remove the needle and place it back onto the stem to reflect the current correct engine temp and you should be good.
Yadayada ,don't know where you came up with that . This vehicle has just one ECT - engine coolat temp. sensor . It's an input for the PCM - engine computer . The PCM sends this info to the instrument cluster over the class2 serial data bus. . The proper way to diagnose a problem like this would be to hook up a professional scanner an check input data to the PCM , an instrument cluster . Not guessing an replacing parts .
Engine Coolant Temperature Gage
The IPC displays the engine coolant temperature as determined by the PCM. The IPC receives a class 2 message from the PCM indicating the engine coolant temperature. The engine coolant temperature gage defaults to 60°C (140°F) or below if:
• The PCM detects a malfunction in the engine coolant temperature sensor circuit.
• The IPC detects a loss of class 2 communications with the PCM.
What engine ? could have come with a 3.4 or 3.8 L .
Engine Coolant Temperature (ECT) Sensor (L36)
Left side of the engine, below the thermostat outlet
Engine Coolant Temperature (ECT) Sensor (LA1)
LH side, top of the engine
Both are close to the thermostat housing , do you know what an where that is ? Follow the top radiator hose to the engine , should be near there . Look at the new part ,can't you match it up.
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