I posted a little while ago about a problem I was having with my heater. I'm not really sure what's going on, so I'm hoping someone can help me. Here's the issue that I've replicated several time now.

Starting with a cold truck, the heater starts to get warm as the engine temp comes up. The heater hoses are warming up too, indicating that the coolant is circulating like normal. As the engine temp gets closer to operating temperature, the heat goes away. I can feel of the heater hoses under the hood and all of them are cold. Even right at the engine. The top radiator hose is cold also. I can wait a little longer till the thermostat opens up, and the top radiator hose will get hot, as well as the heater hoses, and I then have heat again.

The radiator tank when cold looked like it was about mid ways up the tank, which seemed like it was low. However, when I look at it after the heat goes away as described above, the coolant level in the tank was full. As soon as the thermostat opened up, it dropped way back down. I'm afraid if I add some, it will just push it out.

What do you guys think?

 

I would have the thermostat checked out ; sounds like it's faulty. The coolant level should rise and fall like you see.

 

Would the thermostat cause the heater to stop circulating though? I thought it was independent of the radiator as far as the circulation goes

 

Yeah the thermostat will cause issues.
Also check the blend doors?

 

So I put a new thermostat and gasket in yesterday, and I've still got the same problem. I also have a new symptom that's happened before and after the new thermostat. It's done it twice. The engine temp will get hot, like all the way up of the gauge, then drop back down, like a bad thermostat. After it did this, the engine temp stayed normal

 

I have been told the only thermostat that will work properly in a Ford is a genuine ford part.

 

Is there something I can do to test this? I hate to go buy another thermostat if that's not the problem. I would have figured a bad thermostat would have done it all the time

 

Test it in boiling water


http://mechanics.stackexchange.com/questions/23767/how-can-i-test-my-thermostat

 

I've changed the thermostat again. Same issue. Thermostat is installed spring down, oring on top.
does anyone have and ideas?? Every time i drive it now when it's cold it will overheat, and if I fill up the tank to the cold mark, it will push all that out.

Help please!

 

Sounds like you and I are having similar problems

 

Not sure if I can help here or not. I had a '99 F250 in the shop that would not get hot. The engine would not reach 150 degrees. I changed the thermostat and that did not correct the problem. I clamped the upper radiator hose completely shut and drove it around town and on the highway and it still would not get hot. I bit the bullet and put a second thermostat in against my better judgement and it still wouldn't get to operating temperature. I finally put a piece of cardboard in front of the radiator and it would get up to 190 degrees. The heater wasn't as hot as I liked so I back flushed it at the heater core nubs. It gets hot, not as hot as I would like but is acceptable. I flushed the whole cooling system and it still didn't gain any more heat. I think it is what it is.

By rights it should be boiling over with the blocked off radiator and it isn't building much pressure at all. I'm still scratching my head on this one. Oh yea, blend door is working properly. I already confirmed that.

 

So the truck has started overheating regularly now. I went to autozone and rented a block tester that is supposed to detect exhaust in the coolant, and it seemed to indicate that's what I had going on. Went to a local mechanic to get his opinion on it, and he says I have a blown head gasket causing it. So...I guess my oil leak that started recently on my head, has cause a coolant issue too.