One day, I went to McDonalds and the coolant buzzer went off. I checked the coolant level in the reservoir and it was in between low and full. The water neck also didn’t have any water in it. I filled it up as necessary and decided to check up on it again when I went home. This time, I found the coolant over the full line, about 2 cm, and the water neck empty. I sucked some coolant out of the reservoir, so it was at the full line and added water to the water neck. I drove it around some more, came back, and found the coolant to be about 5 cm over the full line and empty water neck. Anyone have any ideas? Thanks.

 

is the car overheating? Is it boiling out the overflow? How new is the Radiator cap?

 

well, mine was thrown out in favor of a dessani water bottle because i can actually see the contents of it withought looking over it

 

Firstly, the low coolant warning is telling you the radiator level is low, so topping up the reservioir won't help. Secondly, when the coolant heats up it expands, and the excess pressure is relieved into the overflow reservior. When it cools it gets sucked back in. So the reservior level is supposed to rise and fall. The LOW and FULL lines are for when the coolant is cold, and a hot reading will be higher than when it's cold. It doesn't matter if the level is above the FULL line when hot or cold.

Make sure the radiator is full and you bleed the cooling system of all air. The best way to do this is to idle the engine with the filler cap off. Let it get up to normal operating temp and keep topping it up until no more bubbles are appearing.

 

^ NZ that will get most of it out... but honestly what I do to make sure it's ALL out... is let it idle with the engine on... fill it up... fill up the reservoir (up to the full line at least, over if you want... it won't hurt, it'll just go out later if it expands too much) and then put the cap SQUEEZE THE TOP HOSE (that goes to the water pump from the radiator) (NZ I thought you told me to do this too? It's archived... which this guy should've searched for btw... heh) and WHILE SQUEEZING IT (squeeze it gradually) put the cap on. You'll spill water doing this. NOW when you release the squeezed hose what should happen is it should suck some water in from the reservoir.

That's how I make sure it's full and no air.

Now another thing to do now that the cap is on... rev the engine up. The water pump barely moves ANY water at all and DOES NOT move any air if it's trapped inside the engine. So you could do this whole procedure and still have air in there. There is no sure way to get it all out no matter how you look at it... if the air pocket is in a weird place it will take a heavy flow of water to kick it out... and then if you keep pushing the water around (driving the car) it could end up back in the engine. The idea is that it will go out through the cap though.

Oh. damn, one more thing I almost forgot... when you let the radiator warm up with the cap off... turn the heater on full blast.

But BEFORE you do that.. if you've noticed your passenger or driver's side floor to be DAMP or WET. DO NOT DO THIS. If you notice the floor is damp, your heater core is probably leaking. In which case, turning on the heater (at any time) will leak air into the system. So don't do it. It still WILL leak a little air into the system, but turning on the heater makes it MUCH WORSE. If you find this is the case (you feel even a little dampness on the carpet... because it's very thick, it actually takes a bit of water before you can feel it... unless you pull it up and feel underneath) then check your coolant levels regularly and do the topping off the way described above without using the heater.

My car is like that right now... I'm not afraid of doing things, but I've pulled the dash before, I'm NOT crazy about doing it again... so I'm doing without a heater for the time being... which is fine considering it's been hot here to melt a stack of CDs in your car. ;(

--Gary

 

There's a *tiny* leak somewhere in your coolant system.
The leak is enough to vent vapor pressure but not too much coolant.
On Kouki FC's, check the thermostat cover cause they tend to crack.
On Zenki FC's, check the plastic filler neck on the thermostat cover as these tend to crack also.
Look for the telltale white lines or discoloration in the black / dark plastic.

What happens is pressure builds and bypasses into the reservior.
Once it starts to cool down, the engine sucks air from the leak and not from the reservior.
Result?
Engine gets hot; reservior fills.
Engine cools down; reservior stays full.


-Ted