It began with the summer day I got the car (90 GTU, 116K miles, very clean and strong motor) running again after a new TPS and repairing a frayed wire to the BAC. The Low Coolant Buzzer hit me. I thought I had lost too much coolant when disconnecting the hoses up in the throttle body are, so I refilled and drove for a month or so. It went off again - and the overflow tank was at it's full mark. I added to the radiator and drove. It happened once more before putting the car up for the winter.
Almost thru winter, my beater lost it's brakes and I got the GTU out and put 100lbs of kitty litter in the hatch for something close to traction in the snow/ice/slush/etc of Michigan roads.
Now the buzzer starts going off and on quite a bit - with the overflow tank was filled to the brim. I did find a pinhole leak at the thermostat, but it only leaks a tiny bit until the engine reaches operating temp, then closes up. Then the scariest thing - I was idling in my friend's driveway and finding coolant just dumping out of the overflow tank's overflow hose!
A new radiator cap (13lbs) and it's still filling the overflow tank. The buzzer went off again this morning. Tonite the thermostat is getting replaced and a good hi-temp silicone gasket to seal it up.
Is this motor toast? Do I have combustion chamber pressure pushing my coolant out thru an internal leak? I fear the worst.

 

is it smoking alot? is the resevoir tank bubbling? my bros. 88 gxl just bit the dust, and it had the same problem. he saw coolant on the plugs

 

Sounds like you need to bleed the coolant system. The pressure from hot air in the system is causing boil-over. Do a complete coolant flush and fill.

Also, what Grimlock said too. Any of those symptoms?

- JB

 

You have reason to fear if it still does it after replacing the thermostat. Also check the integrity of the hose b/t the overflow and the filler housing or whereever it goes on your model.

 

With the car COLD, start it, and take off the rad cap and look for bubbles. If its bubbling at start-up you have a coolant seal problem.

If it only does it w/ the engine hot, its probably a coolant system problem

 

Normally when the coolant system is pressurized, the cap opens up and coolant flows to reservoir. When the system cools down, the reverse should happen, allowing it to draw back to the system. Since you have a hugh leak, it only draws back air throw the crack so the coolant in the reservoir stays in there and gets fuller each time.

 

Much thanks, FC brethren. I will look for bubbling and definitely get a fill-n-flush tonite after I get my new thermostat in. And make some sacrifices to the rotary gods...

 

yeah, on my '92 Civic I notice it usually takes fluid OUT of the reservoir tank

 

How does one go about bleeding the coolant system?