Monte Carlo Temperature And Gas Gauge Problems

Question:
I drove 40 minutes to my parents and back and noticed the temp gauge on the dash stop working. I had the temp gauge sensor replaced. Worked fine for about 10 days driving back and forth to work ( about 10 minutes each way). Went back to my parents ( 40 minutes each way ) and the temp gauge stopped working again. 2000 Chevy Monte Carlo SS. 3.8L. Work done to repair this problem = temp gauge sensor replaced.

Answer:
We need to find out if this IS a gauge problem, or the actual coolant temp. goes low. When the gauge stops, do you notice it just all of a sudden drop to Zero, or does it slowly go low over a period of a minute or two. Basically, can you watch it fall, or is it instant. When you notice the gauge low, do you still have the same amount of heat coming out of the heater vents, or is it a little cooler?

VISITOR REPLY:
It all of a suddens drops to zero. I still have heat coming out of the vents.

Answer:
I am still wondering if this may be a stuck thermostat, causing the coolant temp to drop after extended driving. If you do no think that is the case, try tapping on the top of the dash with the key on to see if the needle will jump back up to where it should be. This will sometimes cause a faulty dash gauge cluster assembly to act up, or fix itself. A replacement would be needed if that were the case. Have had many problem with the steeper motors inside the cluster that cause problems with the Tach and Speedo.

The coolant temp gauge gets an input from the Powertrain Computer (PCM). The PCM gets coolant temp from the sensor. Make sure the wires at the sensor are good and do not stretch from the connector. This would be from a broken wire.

A scanner is really needed to check what temp the PCM thinks the coolant is at. If it see, say, 190 degrees, and you are sure the engine is warmed up,, then the gauge cluster or wiring to it from the PCM has a problem. If shows low temp, then a wiring problem from the sensor to the PCM is a possible cause, as well as the PCM itself. A scanner can also control the gauges needles to tell if the wiring to it, and the gauges are OK.

Follow the wires from the sensor to the PCM, which is in the air cleaner box. Move and tug on the wires while watching the gauge with the key on to see if it moves. This would indicate a wiring problem in that area. Have had some broken wires as the main harness comes out of the PCM and goes up along the drivers side of the radiator toward the top of the engine. A problem with the temp sensor signal to the PCM will usually cause a code to be set, maybe not a check engine light, but store a code for the sensor.

Question:
My gas gauge stays at full except when the acc. Key position and when sitting at a red light it seems to level off when moving it stays at the full mark. 2001 Chevy Monte carlo.

Answer:
See piture below. The problem you are having with your Monte Carlo is that the fuel level sensor inside the gas tank is malfunctioning. The float attatches to an arm that has little metal fingers on it that touch a resistor board to indicate what level the gas gauge should show. When these fingers on the sensor deteriorate, the readings become erratic and inaccurate, and will often times keep the gauge on full or empty.

You would need to replace the fuel level sensor inside the gas tank. It is attached to the fuel pump, but you can buy it separately. You can drop the gas tank to replace the sensor, but there is also a small access hole located in the trunk behind the spare tire well. Be careful when changing the sensor, as the plastic it attatches to can break easily. Also, make sure to run the wires carefully so they don't get pinched when you reinstall the pump assembly.