I have a 91 e150 I6 w/ 190Kmi. I just had my mechanic replace the fan clutch and the water pump. I think he might have not burped the system b/c of the following scenario:
Truck is cold, i start it up and within the warm-up period the temp gauge reaches the "m" in normal and them shoots down to below the "n". It then slowly heats up to the "r" where it operates till the truck is turned off.
I realize that the gauge shooting back down is a result of the thermostat opening up, however i dont understand why the temp rises that high, that quickly. It also has never acted this way for the life of the truck.

so if he never burped the system, what is best way to burp it? or is there another problem hiding elsewhere?

thanks for your help in advance
-jeremy

 

Normally I will just park it on my driveway when the engine is cool( because it is uphill, which is the KEY.......you want the radiator filler neck to be the highest point in the cooling system ), take off the radiator cap, and let the truck run until the thermostat opens ( You will see the water inside begin to move ) and then add fluid until it wont take anymore. When youre all done, just replace the cap and youre good to go

Just do this for a minute or so after the thermostat opens and that has always worked for me. If your driveway is not uphill, I guess you could SAFELY jack up the front or put it up on some drive ramps.

Hope that helps...

 

Don't forget to turn the heater on the hottest setting and the fan on high