Ive seen really wild things happen with s-10s. For example, a 1994 (old body style) has 2 knock sensors, one on the back of each cylinder. They have 2 coolant temp sensors. 1 for the computer (the little one on the lower intake manifold) and another for the gauge that is on the driverside of the engine, between the exaust manifold. Looks identical to a knock sensor. I did an engine swap in one of these, and everything was fine. Except the temp gauge said it ran 30 degrees cooler than it actually was. Sure enough, when transfering the sensors from the old engine to the new engine, they had a plug where the temp sensor (for the gauge) would go, on the driver side of the engine. I put the knock sensor in that spot, and the coolant sensor in the back of the head-where the knock sensor would go. Keep in mind the knock sensors, and the coolant sensor for the gauge are IDENTICAL! That was also on a 1994, it has changed since then. But that goes to show that these things arent as simple as everyone thinks.
Back to the subject, your truck doesnt have any air-bleeders on the upper coolant tube like a 3.1, 3.4, 3.8 liter engine. The air will be pushed out by the waterpump. You said your air is only warm, not hot. It should be hot. Change the thermostat, and while your in there, use a garden hose, and flush out the system. Use a drain pan of course. 1st flush the radiator, remove the lower radiator hose from the water pump, and remove the upper radiator hose, blast water through the radiator through the upper radiator hose. Make sure you have adequate flow out of the lower hose. The block usually never clogs up, but its a good idea to flush that out as well. After that, undue both hoses that goe to your heater core (they are located on the firewall one above the other) make sure u have adequate flow through that. At this point, make sure you change your thermostat. Should have no more problems. This process, along with replacing the thermostat should take no more than 1 hr. I feel as I am writing a book, hahaha. Let me know if this solves your problem. Good luck!
Friday, October 1st, 2010 AT 11:19 PM