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Just changed my coolant today. I use 50/50 standard glycol (green stuff) and distilled water - due to the temps the car sees in the winter, and the fact that it never sees high enough temps to tax that mix cooling wise. It also gives me better corrosion protection.
So, did it in the garage, and afterward started it up and drove it into the back yard to wash (yes, I warmed it up completely). After washing, I started it up to move it back into the garage, and for the first time since I bought it over six years ago, I got the low coolant buzzer. Man is that thing noisy! No wonder so many of you panic when you hear it! Of course, this was because I wasn't finished "burping" the system.
So, back in the garage, after letting it cool off, I decided to try the funnel on the filler neck trick - only I didn't have the Lisle kit - but I did have a funnel with a thick tip that wedged into the filler and didn't leak. Poured in distilled water to top it up and half filled the funnel once I got all the bubbles out (squeezing the upper rad hose repeatedly). It was very interesting when I started the car. I got more large bubbles out, of course, but as it warmed up I started to see very fine bubbles - kind of a "mist" in the fluid - they showed up as I reved the engine. These are the "tiny bubbles" the AST is supposed to deal with. When I reved the engine the level dropped, and came back up when it returned to idle. If you try this (operating the engine without the cap - therefore having the system at atmospheric pressure), remember it is much easier to boil the coolant as you have no pressure in the system. I quit before it reached operating temp. - call me chicken. Oh, and no, the tiny bubbles are not combustion gas - those bubbles are larger.
I did have the throttle body hose off when I refilled BTW, so even when you do that you still have to burp the system a few times to get all the air out. Also, when I drain the system, I remove the rad. plug from the bottom centre of the rad. and after it's empty then the bolt at the bottom centre of the engine under the spark plugs right above the oil pan - its on the centre housing - for those who don't know about the "secret" engine drain plug - it's a 14 mm head bolt with a copper washer. Don't drain the engine if it's been running unless you wait at least 5-10 min. so all the extra heat in the metal goes into the coolant. Also, be careful, the coolant that comes out of the engine drain plug is much hotter than that which comes out of the rad.!
1993 RX-7 CYM base