Ask expert's help for my 94 Toyota Previa's coolant system problem.
The coolant can not flow and engine temperature is very high. However, when I drove up to hill, the coolant can work and the temperature is down to normal. I thought it is the thermostat problem. I drained the coolant out and only got about one gallon coolant, 2/3 gallon form radiator and 1/3 gallon from engine. The coolant tank is still full. Could an expert explain what this problem is?

Thanks

Are you sure you had enough coolant before the problem started to occur? Have you tried adding more coolant ? one gallon doesnt seem enough.

My previa didnt take much coolant either, but i changed the waterpump in the winter and my inside heat didnt work, until i added enough coolant, then it started to heat up and i knew i had about enough to make sure my engine is NOT overfeating and i dont freeze, after all if you fill it up just watch for bubbles and squweeze the FAT radiator hose while car is running and you are pouring in liquid.

The only way to fill it up is thru the overflow container, so If you are trying to flush it out by draining it and it is not draining the overflow container it makes me think that there are hoses that are pluged up with something, but i doubt it.

-Check and see how many gallons of antifreeze does it take?

-You could have a stuck water pump, and that will make it overheat, by not circulating the coolant.

-It can heat up so much that it might eat thru the rubber of the hose that you are losing coolant slowly but surely.

-Start CHEAP, check the cheapest parts that can be replaced before you focus on the waterpump.... which is very nasty, considering that the bolts that hold it could be overheated and have melted into the block, which means thread repairing while chaning waterpump... I hope you didnt drive it far while it was overheating...I did mine and i had to repair two of the waterpump bolt threads inside the block, and pulling them out is HARD AS HELL, i dont care if you have a garage and tools.

By The Way, Im not a certified tech or anything, im more like your learn-as-you-do type of guy and i just get down to it and get dirty with it. I hate not to have a dependable ride. Good Luck