Engine is overheating?

can you please tell me where the thermostat is located and how i test it?

On the driver side of the engine, there is a radiator hose that connects to the engine just under the wires for the spark plugs. There are two bolts. Remove the bolts and pull off the hose. Some coolant will leak. Remove the old thermostat and gasket



Pull the thermostat out of the housing with your fingers. Take careful note of which way it sits so that you can reinstall it or its replacement in the same position.

Put the thermostat in a pan of water on the stove, and turn the burner on high.

Monitor the water temperature with an oven thermometer. The thermostat should open at about 195 degrees F if it is functioning properly.

Replace a faulty thermostat. Reinstall it if it opens and closes properly, and look for another problem in the cooling system.

Here are the facts:
1) If I drive above about 35 mph, the van will suddenly "overheat" according to the gauge.
2) However, it is clearly not a faulty gauge, because the heater gives off no hot air at all.
3) Even when running normally the engine heater gives off no heat.
4) NOTE: When it overheats, if I pull over and shut the engine off... and wait like only 1 or 2 minutes... and turn it back on, the temp gauge returns to normal!
5) Again, if I then start driving again and stay below 35 or so mph, and do not go up a hill, the gauge will read normal.

6) I have had thermostats go bad, water pumps go out, hoses break, fan belts break and radiators lose all their anti-freeze... in such cases and the engine overheats... it takes a looong time for the engine to cool back down. With my current problem, it takes just a minute or so?!?!?

7) I have replaced the thermostat, and had the system flushed out, but it has not helped.

What say you?

If the radiator is not clogged-up and cooling fans coming on could be a bad thermostat again or airlock in the system, try bleeding it- if it continues to overheat get it block and pressure tested this will identify a blown headgasket cracked head or block or and intake gasket leak

What would make a car overheat when driving in town with the A/C on and then cool down when A/C turned off and accelerate.

A couple of basics, I have no idea what type of car you have, cause you didn't tell us! Generally, the cooling fan isn't doing an adequate job...front drive has an extra fan see if it comes on when a/c is turned on. Rear drive, clutch fan is weak.
Dirt accumulation between condenser and radiator!
After 35mph the engine no longer needs a cooling fan!