My temp. guage (1996 5.0L 4X4 North Woods Edition F-150, 218,000 Miles) is constantly going up and down but never cresting the midway point of the gauge. I am wondering if this is a sign of pre mature water pump failure? It has NEVER been replaced and I am thinking that I should change it for preventative maintenence. Any suggestions?

Also, I have never changed a water pump on an F-150 before. Does anyone know how hard it is to do and how much time I will need to invest?


Thanks for all of your comments!

 

My opinion, I'd check the sending unit or gauge. Factory gauges are electrical unless you've put aftermarket mechanical gauges in.

 

I have this same problem, but I have a new water pump. I think the gauge "hunting" is caused by a bad sending unit, or temp. sensor. Its located in the lower intake. I have replaced everything in the cooling system except the sending unit, and radiator.
As far as the water pump its not that big of a deal normally. If yours has never been changed you probobly should soak the bolts for awhile in PB or whatever. The only concern is braking bolts. I was careful and fortunatley didnt break any bolts tearing down my 351W. I would say two hour job if you take your time.

 

It could also be air in the system. How's the coolant level? When was the cooling system flushed last? Changing a water pump isn't hard on a 302. Couple hours, just be careful not to break a bolt, that will make it a lot more complicated.