Overheating, two part question.

[Diff Whack Daddy]

Part one, will leaving the 02 sensor unplugged cause an overheating?

Part two, how would one go about testing the water pump?

The first thing I will replace the thermostat, but I want to get this done in one shot. Thanks to all that can help.

 

[Doug]

I have driven around with no 02 sensors and haven't had any problems except for a CEL. A couple of months ago I thought my water pump went. I let the truck cool down and then took the radiator cap off. I waited for the t-stat to open and then i revved the engine and i could see the water moving through the motor.

 

[Opera House]

If the pump isn't leaking, its good.

Sometimes the leak can be very small so you have to look for water traces at the weep holes near the pump shaft. One common problem is the pump leaks just a little. When the engine cools down, it sucks in air instead of coolant from the overflow tank. Then you get a big air bubble in the system. When the engine is completely cool, remove the radiator cap and make sure the level is all the way up to the top. Both of my Explorers have had problems with the factory thermostat. They are notorious for having problems.

 

[Texan01]

100% of the time the pump is leaking it's bad, but no leaks does not necessarily make the pump good either.

My pump was not leaking, but the casting and the vanes were all eroded away from cavitation. (what 7 years of not changing engine coolant will do) I also had a 75% clogged radiator, a dead fan clutch, and a bad t-stat.

My pump was flowing coolant, but not very well. so 100 bucks for a new fan clutch and water pump, a new t-stat, and 200 bucks for a radiator, 3 flushes and some water-wetter and the X runs as cool as a cucumber.

 

[Diff Whack Daddy]

I am going to reconnect the O2 sensor and swap ou the t-stat first thing tommorow morning. If that doesn't fx it, the I know it's the water pump as there is no rust in the radiator and it looks like a brand ne aluminum one. At least it's moving now.

This is the $350 1991 tht I bought.