Temerature gauge

[OGCollard]

So driving down the highway with engine at temp, when i hit the gas sometimes the temp gauge slowly drops to the line right above zero, holds, then comes back up to 210. It is not leaking any coolant, oil and oil pressure look good. What could be causing this? It is on my 99 4.0

[nickyg]

loose wire or dirty connector comes to mind

[OGCollard]

Well i unplugged it and cleaned it up, added some dieelectric grease and plugged it in tight. Some folks suggested and air bubble caused by weak radiator cap, i tried burping it and running it to temp with cap off, it rally did not drop any coolant and put new cap on. We will see in morning on hwy.....

[OGCollard]

If i recall correctly the thermostat is a mechanical thermostat. That sensor if it were to go bad on the road will not prevent the thermo from openin correct?

[4.3LXJ]

That would be correct

[downsy]

Sounds like a chaffed wire. You said when you hit the gas it does it. That sounds to me that when the engine is torqueing in the mounts that it's moving the harness and grounding a wire out some where.

[OGCollard]

Well, 60 miles worth of hwy today and no fluttering temp gauge! Keep an eye on it while driving to work this week and all should be good. Hopefully my buddy can come over tomorrow night with his computer so we can diagnose the idle dying on the 2000

[abebehrmann]

If i recall correctly the thermostat is a mechanical thermostat. That sensor if it were to go bad on the road will not prevent the thermo from openin correct?


Just remember that the temperature sending unit and the thermostat are two separate pieces that work independently. Thermostat opens and closes to allow coolant through the radiator, the temperature sensor sends signal to the gauge and computer.

If I had to guess, it would be either the temp sensor is on its way out or you have a loose/chafed wire somewhere.