Bubbling coolant

It was running hotter than normal because you were way low on coolant. The bubbling I would attribute to trapped air. You want some coolant in the reservoir at all times so as the engine cools it doesn't draw air into the cooling system.

Seems you're halfway there - getting the level to an okay point. Now you need to track how much you're putting in to keep it at that level.

It was very low on coolant. Have now discovered a hairline crack along top of rad near the cover - that might explain the need for extra coolant! Thanks a bunch:)

Is it the original radiator?

I just replaced the original one in my '93. Not bad for plastic.

To lose that much coolant, sounds like a blown headgasket. To test for this, you should see large amounts of steam from the exhaust. The classic test of removing each plug and cranking the motor to check for water-mist from the spark hole is not possible for the back plugs, being a V6.

If it is a blown gasket,..the engine will run rough especially when cold as the splug involved will be wet.

Jason

Check the color of your oil if it looks milky it indicates water in it.