Water Pump ?
 

I have read all the cooling system threads ( I think) and did not find an answer.

My friend has a 93 1.6, probably doesn't make any difference which model car it is - anyway, he pulled into my place and you could hear the coolant bubbling tremendously and going into the overflow. He was complaining about the car heating up on the way over to my place. After the engine had cooled the over flow was full to the top cap and the radiator when we popped the cap was empty in all of the top section.

Is this possibly the water pump or possibly a bad thermostat?

He has not had cooling problems before, had the car stored for a year or so while in Iraq. He did check that the coolant was OK, had only driven it a few short trips before this problem happened.

I am not a cooling system guru, just the opposite, but they seem pretty straight forward. I am thinking thermostat. All the electrical connections seem clean, the fan is running and it's voltage is good. When you turn on the AC the second fan runs as well.

Any help would be appreciated. I may change his thermostat and then flush the system, water it up and see where things are at. I did not check that little hose off the thermostat housing, will do that when I change the thermostat. The car has about 110K on it and he has been right on with his maintenance, the coolant was new when he put it into storage.

Thanks in advance for any suggestions or advice.

just change out the thermostat and radiator cap. total about $10 and 30 minutes of your time, and its good insurance. then fill up with water and give it hell. sometimes you can also have an air bubble in the radiator that'll prevent the coolant from touching the thermostat and opening it. try filling the rad with water and running it with the cap off for a couple minutes

Indeed- bubbling and a full overflow tank does strongly suggest a bad radiator cap. In case you're not aware, the cap itself acts as a pressure regulator- it is designed to hold a set relative pressure inside the cooling system (to raise the boiling point of the coolant) and relieve excess pressure by venting into the catch tank. If the cap is not holding pressure, it'll vent too much and lead to boiling of the coolant.

The thermostat is also nice, cheap insurance.

You can check the thermostat by putting it in boiling water on the stove and see if it opens.

Thanks for the info guys, I think I will go get a thermostat, maybe test it befor I put it in as well. He has a new cap, I know that means nothing, new stuff can be bad too.