My buddy was driving me back up to my home on the interstate the other day and We noticed his temp gauge was going back and forth.. It usually stays right in the middle. This thing was going from the middle to almost overheating and back down again and again and again. It was really playing tricks with us. We pulled over and the damn thing was steaming.. We added the necessary amount of coolant and water mix, but it still played games (it wwas pretty much stationary while staying under 75mph) (anything over 75 and it went whacky).

Anyway, could it be a leak in the radiator? Could it be a water pump malfunction?

 

So it was steaming... From where? Something as simple as a bad radiator cap can do that. Start with the basics, just like any other kind of car. If it's leaking, you gotta find the leak.

How old is the thermostat? Maybe it was sticking.

Then check the radiator for being plugged up with crud. Maybe it can't handle the cooling load any more?

Water pumps usually fail either of 2 ways. The bearings get loose & they make lots of noise. But they still pump water. Or the seals start leaking. But they still pump water. It's a lot less likely that the impeller fell apart so it doesn't pump.

 

im gonna say its the water pump and/or fan clutch. That just happened to me and it was doing what you said. if you go to replace one, make sure you replace both, do it right

 

leak in radiator would result in it going to the "H" - happened in my mom's van and there was a leak. didn't go down, just steadily rose.

 

i would change the thermostat and go from there

 

if they are no leaks i would go thermostat first. then go with the water pump.


maybe even check the wiring for any short. like the wire that sends info the to gauge cluster.