Hi, i have a 2000 Ford Ranger 3.0L 2wd. A few months ago it started leaking coolant above the tranny. I was told it was a gasket or seal at the timing belt cover? So they put some stop leak in the radiator and all was well for a few months. Well a few days ago i was going out to lunch letting it warm up (I live in Pa.) I noticed it was blowing almost cold air. So when i got home i also smelled coolant and it was leaking toward the front. It was over a half quart low.

So i took it in and they did a pressure test. They replaced the timing cover gasket, water pump and thermostat. When i left the garage i noticed the heater gauge needle going a little haywire. It would read halfway, then jump down fast towards cold, then back up. It would blow hot, then warm, semi cold air until i ran it about 15 minutes. Then it was so damn hot i had to turn it off.
I just ran it today and the heater gauge needle is doing the same thing. I let it warm up for about 10 minutes. When i jumped in the needle was buried on Cold. I drove 1 minute and it jumped up a little. The needle is going up to halfway , then down to 1/4 cold, blowing semi-cold air, then hot, then cold again. The needle didn't stay at the halfway mark and start blowing hot air all the time for about 20 minutes.
I am about to take it back in the shop. Any of you Ford techs know what is wrong with my baby?

 

It might be that you have trapped air inside the cooling system.

Start to run the cold engine with the radiator cap off. Watch to see if any large amounts of air bubbles rush to the top of the radiator after the thermostat stays open.

After any air bubbles stop showing up, put on the radiator cap and see if the temperature gage is still twitching.

If all is well, let the engine cool then check where your coolant level settles at. Add coolant as required to the radiator and the overflow bottle.

Keep us posted!