So this is the second mustang I've had that does this magic trick. I come back from cruising and pop the hood and there is hardly any coolant in the overflow tank. The car never even comes close to overheating. The temp stays around 190. But I notice this while the car is hot so I fill it to the "HOT" line and then I let the car cool. A couple days after I will check it again and the coolant is back to where it was. Just wondering if anybody else experiences this or knows where this coolant disappears to.
Oh wait, he said it returns if he leaves it sitting.. Thats just the overflow from when the engine is boiling it will build condensation and slowly fill..
---------- Post added at 12:57 PM ---------- Previous post was at 12:55 PM ----------
Make sure all the air is out of the motor. Take off the radiator cap "when cool" idle engine to around 2800-3200 let the water level lower when t-stat opens then top off and return cap with the idle revved. that may help.
Heater core is bypassed and the exhaust is clear as day. There are no leaks anywhere on this car or my 88. The reservoir is just never at the "HOT" line when the engine is hot. I can go months without putting any coolant in it and even on the hottest days and I'm stuck in traffic the temp won't go above 210.
It is just doing what it was designed to do. It catches any excess when the engine does not need it and allows it to be drawn back into the engine when it does. No magic, no mystery, just working the way it is suppose to. If it is not on the "Hot" line when the engine is hot you may be a bit low on coolant.