I have a 17 year old Ford Ranger with about 90k miles. (Several years ago the truck was overheating and I had all of the cooling system replaced, including the radiator, which was clogged up.) Lately I have noticed that the temp gauge arrow is going up rather high before falling back. If you consider the temp gauge as going from zero to ten, I estimate that the arrow goes up to eight before falling back to around three. Then it goes back up to eight and repeats the cycle. Should I be concerned about this? Is the truck in danger of overheating? Is this most likely a thermostat problem? My expectation is that in cool weather such as we are having now, the arrow should hover around three or four and never go up to seven or eight. Thanks, Sam
on a scale of 1-10 i'd say the truck should run consistantly at 5. it might be a thermostat problem but more than likely i would check into the fan. if it's an electric fan the sensor may be failing and giving the signal too late to keep it in the middle. if it's an engine driven fan i would check the fan clutch.
I would replace the thermostat as soon as possible. It sounds like it is letting the water get a little hot before opening up to let the radiator cool it down. Just my opinion. ray allen
I too, would change the thermostat. Don't get one of those $3.00 card thermostats of the rack, get a good one from the counterman. But it also sounds like you might have air trapped in your cooling system. It will heat up and then the water expands and finally comes into contact with the thermo and suddenly cools it down. This heating and cooling of your engine is not good, it will eventualyy warp your head. Also, absolutely NEVER run your vehicle for more that a test start up (a few minutes) without a thermostat. It causes your engine to heat up unevenly. greg
Air trapped ??????? (( Now of course this is done only after you know the heat sensor and fan are good.)) Fords have a weird quirk - like someone else mentioned - some times air gets trapped in the heater core and hoses. They sell a "T" type fitting usually plastic(almost any parts store) - its for flushing your system.(usualy made by Prestone) Any way - you put it in the hot water intake (smaller hose not the rad hose - about 1 inch diameter) side of the hose just before where the hose goes into the heater box(in the engine area - near firewall) - REMEMBER ! ! Don't do this until the vehicle is "COLD" - with engine OFF ! ! ! After you remove the radiator cap - screw your garden hose onto the new fitting. Turn on the water - low pressure - not all the way open - a garden hose can deliver any where from a few pounds pressure to 50 lbs or whatever your street/house pressure is. You'll also need to slide the heater lever open all the way in the truck. This will allow water to flush through the system and flush it - most guys only flush the radiator even when doing thermostat changes and such. After you see all clean water coming out the radiator cap for a couple minutes - shut off the hose. Open the drain valve at the bottom of the radiator and turn the hose on again - slow ! That will flush the system again(including radiator). After a minute or two and if you see all clear water -shut off the hose and remove it. Close the drain once empty. Replace the cap on the "T" adapter you installed. Your almost there - sounds like allot - but this is the safe way. Now if your going to replace the thermostat - do it now - you should get either a new "O" ring or a gasket depending on year of truck engine.(The part store guy can look it up. When thats finished - refill radiator with water or whatever mixture of antifreeze you choose. Replace the radiator cap - Just remembered - make sure you have the correct cap - on the under side of the cap are numbers - that too is set for a given LB(pound) rating - its designed to open and release pressure or let water go into the radiator if needed. Again the parts store guy can look that up. OK - lets see we flushed - changed thermostat and gasket - refilled radiator and over flow tank if needed - Now start your engine - with heater still on - running your engine at idle until you see it warming up a little - now increase the rpm's a little and hold it there - DON"T race - just a little faster than an idle and hold it - when you see the gauge or needle move into the normal zone - hold it and watch the gauge - once you see it drop a little ( if it goes into the danger zone - (SHUT IT DOWN)- take your foot off the gas - that should have expelled any air in the heater lines and such. If there are no leaks and such - go for a ride - not too far and bring a jug of water just in case - leave the heater on - if the gauge reads normal and things seem fine - you got it -let us know how you did ! ? !op:
Last week I finally took the Ranger to the garage. I got the truck back today. The mechanic replaced the thermostat and the sending unit without producing any improvement in the gauge readings. He concluded that the cooling system was working fine, that the water is not getting too hot, and that the gauge is defective. He could not find an OEM gauge but offered to install an after market gauge for about $150, parts and labor. I am going to look for an OEM gauge. Thanks, Sam
