Jul 29, 2008
-   I have the same symtoms on my Ford Ranger (2002) Needle suddenly jumps from normal to red, by the time I notice and maybe drive a tenth of a mile ( the time it takes to run wicked bad thoughts through your mind) and finally decide, Okay.... I'll pull over.... apply turn signal and brake and Viollah.... needle returns to normal. I have become a parts changer it seems with no satisfaction. Replaced Fan Clutch, Reverse flushed radiator, acid cleaned condensor coil, replaced Thermostat and Housing assembly, replaced water pump, replaced 4 port heater valve, (yes I know that had nothing to do with my problem, but thats the biggest piece of plastic junk I have ever seen and it developed a slight leak just like the previouse three in less than 1.5 years, so I replaced it again.) another reverse flush of radiator, replaced temp sensor, ( which by the way - for those of you who have not found it yet - is located on the rear of the engine close to firewall, very difficult to get hand or tools on but is barely possible with deepwell 3/4" socket, extention bar and swivel knuckle, first need to get a finger on the release clip of the electrical connector. Start by loosining the module harness to the left of the sensor which is mounted through the firewall itself and moving it to the side, allowing you more room to get your left hand in to touch the lil buger.)
Okay, with all these items changednow, now I don't get the rapid needle, not yet anyway, but still overheating after about a 40 mile trip. resovour was filled to max line while cold but after heating up is above the inlet and outlet tubes that enter and exit the resovour. If I go out and restart the engine after letting it cool down completly, the excess water will re-enter the engine and normal level will resume. I can think of only three things I have not done, 1) is change the temp sending unit, 2) possibly air is locked somewhere in the sealed system, and 3) troubleshoot the cooling fan located in the radiator fan shroud. I don't know for sure wether the cooling fan is operating properly, when it should or if at all. I suspect this is where the problem may be but need advise on the troubleshooting process for this, I have a meter and know where the relay is, So if there is someone who can answer this for me, please don't hesitate to write the complete details for checking the relay and the circuit. I have a manual but it only mentions the electric cooling fan once to discuss how to remove it for when you replace the water pump, no diagnostic discussion whats soever. Please Help, I am running out of money and patients, if you can't help please send explosive C4 and a fuse.
Thanks, John "The Parts Changer"-  
joweba