Heats up, then drops off

[BHaley85]

Hey, new to the site. I just purchased a 98 Ranger that had been sitting since 2008 unused. When I got it the truck ran cold all the time. So I put in a new T-stat and now when I start it up and drive It comes up to temp, then after 15 to 20 minutes it drops to cold. The heater blows warm not hot at first, then becomes cold when the gauge drops. After the temp drops, it will rise at idle slightly, but upon acceleration it drops again. Any help would be appreciated, cause I cant afford to take it to a shop. It wont go through its drive cycle to pass emissions unless the temp stays up.

 

[martin]

I would try another thermostat. It's not unusual to get a new one that's lazy or inaccurate.

 

[289-tiger-]

It sounds like the heater core is plugged and has an accumulation of air in the system. If you pull the lines off the core at the firewall and spill just a little of coolant, that would indicate the system is not full, an easy check. I don't know the difficulty rating on a 98 or how much dashboard you have to remove to get to it.

Good luck