massive coolant leak

I have an 89 cavalier with the 2.8 engine. This car is really just the car that sits around at home until someones main driver dies or has to be fixed. It really doesn't go out of town much but it really hasnt shown any issues with out of town driving. Today I drove it on the highway for about a 60-70 mile trip. I actually made a stop to get my girlfriend about half way and the car was fine. When I got to my destination, I turned the car off and we began to hear a noise that sounded like someone had pushed the release valve on their air compressor. Now this also happened two years ago when it went on another highway trip that couldn't have been much more or less than this one. I knew exactly what was happening with needing to get out. All of the coolant began to purge out. I know it comes from the front passenger side. I never saw any issue with the heat gauge. When this happened two years ago, we put water in it and took it to a shop that said a hose came off? Whatever, so they clamped this hose back on and never had an issue from the car again. I don't see how this could be. We put some more antifreeze in the radiator once it was cool since I had some in the trunk. The gauge was not overheating so we drove the car home. When we got home, nothing happened like this. The only thing that seems to be the same from this time and last time is that it was after a long drive and after the car was shut off. If a hose has slipped, wouldn't I be losing coolant while it runs? I know my gauge works because after all the coolant leaked out, I know the engine would be pretty hot. I turned all the electrical stuff on with the key and the gauge showed the pin all the way to the hot end. Possibly the thermostat not working all the time?

If you have an external leak, it should be fairly consistent and easy to locate.

Its possible that you have a cracked head or something that causes the engine to consume coolant.

Hope that helps. Your post is a bit cluttered and difficult to follow.

Oh haha. Well basically ALL of the coolant leaked out somewhere on the front passenger side of the car under high pressure in a matter of 5 minutes. After it cooled I put water in it and it ran fine.

Did you happen to notice if the radiator cooling fan was running when the car was overheating?

Also, there are several GM models out that use a separate sending unit for the instrument cluster gauge than for the PCM and cooling fans. Sure, when the car overheats the gauge may read high, but is it reading accurately before it gets to that point? Maybe not.

Where is the coolant overflow tank / degas bottle compared to where you suspect the leak is?

-Rod

http://i1254.photobucket.com/albums/hh608/eishiba/p_00993.jpg


This is where it was leaking. This hose coming from under the cap on the tank. I filled the tank with water. I'm guessing this hose is some kind of way to release extra water when some kind of build up or backing up takes place? I don't know. What is this hose for and why might it just release all my coolant? The engine is still not overheating when driving it.

That's the overflow. When the cap reaches its rated pressure, it purges through that hose to prevent a hose explosion or similar failure.

The car is either overheating or has a blown head gasket/cracked head leaking combustion pressure into the cooling system. As stated, the engine may have separate sending units for the fans and temp gauge.

Well I don't have any power loss or any smoke so I can't say a head gasket or blown head. I just find it odd that it would wait until after the car is turned off to push everything out through that hose.

You may want to find someone with a cooling system pressure tester and have them test the pressure cap to see if that pressure cap is actually holding the correct pressure. The cooling system relies on the pressure cap allowing the system to build the proper pressure (probably around 15 psi) to provide the correct boiling protection. If the cap is not allowing the system to build enough pressure, it may be allowing the coolant to boil over when the water pump stops circulating coolant allowing the coolant to absorb more heat. If you don't find someone that can test the cap for less than the cost of a new cap, you may want to just replace the cap as, if nothing else, preventive maintenance.

-Rod