I have a 91 e150 I6 with 190K. Within the last year, I've replaced the radiator, upper/lower rad hoses, thermostat, fan clutch and water pump. Pretty much everything in the cooling system has been replaced with the fan clutch and the water pump being replaced within the last two weeks.
When starting the truck after it sitting overnight (cold), the temp gauge rises upto just past the "M" in normal (hotter than normal operating temp) and then quickly lowers down to the "N" in normal. It then slowly raises again up to the "R" where it will stay at until the truck is turned off and completely cools down again.
Is it really suppsed to get that hot before the thermostat opens up? Is this normal for the gauge to bounce around like that before settling at normal operating temp? Could this be a sign of a headgasket leak?
no bubbles. I tried that. I even jacked the front of the truck up while i did that so that the radiator neck was the highest point of the cooling system and ran the truck for about 25 min.
are you losing any fluid? or seeing any oil/antifreeze mixed? I have been having some similar problems and replaced all the same things you have. I am monitoring my fluid levels now to see if I am losing anything. I am going to try adding that water whetter stuff from Redline. Mine is staying at the N and then all of a sudden it goes to the far side of R. Used to always be just under the N no matter what. I'm hoping its just air in the system and I will burp it for a while, but I suspect I have a head gasket leak cause that's the way these things usually go for me.
no oil in the water. no water in the oil. no white smoke or any smoke at startup. I lost a lot of fluid from the overflow tank after driving it once or twice. This I attributed to all of the coolant I lost when I burped the truck with the radiator cap off for 25min. The water stopped spilling out of the radiator when the thermostat opened up but the water didn't go down far enough in the radiator that I ever had to add more ( i thought this was strange).
any ideas big or small would be greatly appreciated
thanks
dbuck50: read the coolant % mixture on the redline bottle. It'll run hotter than normal with a normal 50/50coolant+waterwetter mix. If i remember right it calls for something like 30%antifreeze and 70%water to make the redline stuff work right. I could be wrong b/c it's been over a year since I tried that stuff, so read the bottle carefully before adding.
My 1993 does exactly the same thing. The thermostat might be a little slow in reacting to the temperature changes, but if it never runs hot or loses water I'd say it was normal.
Jeremy, I checked mine closely this morning. It rose to between R & M, then dropped to below N. Then back up to between O & R. Then down to N; back up to between N & O where it stays forever. I am not convinced this is a "problem." I think what we are seeing is the lag time between the moment the thermostat senses a temperature rise and when it opens or closes. If I were to try to eliminate it, I would check the T-stat. I also think F150'89 has a good suggestion to check the temperature sending unit. I'm far from being an expert, but I am not concerned about mine. Good luck on figuring it out, and let me know what you come up with.
Have you noticed if any of your other gauges are reading higher than what they did in the past? If so it could be that the Instrument Voltage Regulator (IVR) has gone out of adjustment and is pulsing the gauges at a higher voltage.
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