I've been trying to figure out why my low coolant lights been intermittantly going on and off... and i've got a theory as to why its happening. I've bled the system yet it'll always somehow come back on again, i thought the sensor was dead since every time i checked the coolant after driving for a bit it was allways 100% full and AOK. But the other day i checked it right in the morning because the light came on after i started the engine... and there was low coolant in the radiator. So I dont believe the sensor was lying.

Anyhow I think whats happening is that i have a 20/80 mixture of coolant to water or maybe slightly less/more. Roughly around there anyhow. I was reading that antifreeze increases the boiling point of water and our systems are pressurized... I'm guessing that if the engine in the summer heat gets hot enough in traffic or whatever then its possible the antifreeze might boil a bit prematurly... which might be why the light comes on some of the time. Some parts get too hot, bit of air bubbles up and eventually gets to the coolant level sensor and trips the light on when it builds up.

Does anyone think that my lil "theory" is likely? So long as the PSI is under 14 (or whatever it is so that as it expands it goes to the coolant resevoir), it could build up, and if its creating gas outside of the radiator and goes above that PSI rating it could actually push coolant out of the system and allow a buildup of gas.

Finally i'm guessing my temp sensor for the ECM is messed up and needs to be replaced because i dont htink the fans are coming on at the right time and causing excess heat unless i have the Aircon on....

Anyhow, just some thoughts and ramblings

PS im not a mech. so this could be completly backward...

 

I think water boils first if not treated with antifreeze.I would go 50-50 balance with the coolant.My02

 

Even if you boiled the coolant and forced some out, the reservoir tank should supply replacement as the system cools. Remember, when it boils, it isn't "air", its vaporized coolant and water, which will condense as the system cools, creating a vacuum, which pulls the coolant out of the reservoir, into the radiator. Check the rubber tube from the reservoir to the radiator fill neck for cracks. That would allow air to be sucked into the system when it cools, rather than replacement coolant.