confused-

[tabahr]

OK, check this out.

My low coolant light was coming on every once in a while after driving a while.

I replaced the sensor on the radiator.

Now, every time I start the car cold the light comes on and stays on. If I start the car warm, no light.

What the heck?? Did I get a bad sensor at the dealer or is there something else in play here?

[Joe 1320]

Most likely the cause is trapped air. Go back and bleed the cooling system again, that should cure the problem. Make sure the radiator is full as well as the proper level in the expansion tank.

[Injuneer]

Check the rubber line that connects the reservoir tank to the radiator fill neck. When that line cracks, it prevents the radiator from sucking coolant back in from the reservoir as the radiator cools down and the coolant contracts. It pulls in air instead. When the radiator heats up, the coolant in the radiator expands, and the air is forced back out.

[tabahr]

I do not believe the problem is air in the system. This morning when I started it and the light stayed on I immediately shut it down and popped the hood. I removed the radiator cap and the fluid was right up to the top, no air.

Good trys.... any other ideas??

[Joe 1320]

Ok...... just know that once the light is triggered, it will stay on even if the coolant level rises back to where it should be until you cut power and restart. It is not uncommon for the level to immediatly drop once the engine is fired up. There is a bypass that flows water even if the thermostat is below opening temperature. You stop the motor, coolant level in the radiator retuns to normal. I would open the cap, start the car and see if the coolant level drops. If you see it rise slightly while warming, cap it before it overflows. It may still have trapped air, it often takes several bleed cycles to purge all of it. There is the outside possibility that the sensor is bad to begin with. Also, bubbles in the coolant from a leaky headgasket can set off the sensor. Hopefully, it's not that.