Erratic Temperature Gauge
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Erratic Temperature Gauge
4.0 AWD 1997, analog temperature gauge swings to the extremes of the Normal range under certain conditions, usually when ambient is above 50 and when climbing hills. I thought that I read once that this was identified in a Ford Technical Service Bulletin as a weak water pump. Personally, I cannot imagine the coolant temperature varying so rapidly. Cooling system has been serviced by nature of many replaced parts, not including water pump. Any similar experiences out there?
Mountain Pass
Joined: Jan 2006
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roving air bubbles in the engine (heads) will cause large fluctuations in temp measurement. The engine doesn't actually change temp that fast, but the sensor does see different temps as bubbles past by or are trapped. A sticky thermostat will also do the same thing, again the engine doesn't really change temp that fast, but large in-rushes of overcooled coolant can show up at the sensor as temp swings.
If it is either issue, get it fixed as the engine is likely running at the highest temp recorder, or higher....
If it is either issue, get it fixed as the engine is likely running at the highest temp recorder, or higher....
Postmaster
Joined: Sep 2003
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From: Southern California
Oh yes, the coolant temperature can and will rise very quickly, especially if you are going uphill. Check the fan for cracks, and also check for a failed fan clutch. I have had fan clutches go bad causing an engine to overheat.
Post Fiend
Joined: Apr 2005
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From: Washington state
air build up in coolant can be caused by failed head gaskets or cracked heads, both of which the 4L is infamous for...look for any oily residue in coolant neck with finger, and tiny champagne size bubbles coming up in coolant at neck while hot and engine runnings....any abnormal unexplained coolant loss of more than a cup a month?
coolant temp swings into the hot zone have to be repaired, drives the PCM crazy and sends it into shut off the torque converter lockup mode which just makes the overheating worse and severely overheats the tranny which is a $2000 killer...can even lock out OD and sets the fuel trim settings to inefficient levels
any PCM codes?
coolant temp swings into the hot zone have to be repaired, drives the PCM crazy and sends it into shut off the torque converter lockup mode which just makes the overheating worse and severely overheats the tranny which is a $2000 killer...can even lock out OD and sets the fuel trim settings to inefficient levels
any PCM codes?
Last edited by 96_4wdr; Jan 26, 2006 at 03:15 PM.
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Radiator is cooled by forced air, if your car overheats when climbing hills only there are a couple of things you can do before blaiming the heads.
When engine is warm open the hood and feel the air forced by the radiator fan.
You should feel a strong gust, and it should be stronger when revving up the engine.
If the fan just whirls around and you feel no increased air flow fan clutch is gone.
To test the water pump output firmly compress the top water hose going to the radiator (careful, it's hot), if it expands you have coolant flow. If it doesn't you most likely have a stuck thermostat.
Sorry, don't have enough experience on Aeroheads, but these guys do know what they're talking about.
Good Luck!!
When engine is warm open the hood and feel the air forced by the radiator fan.
You should feel a strong gust, and it should be stronger when revving up the engine.
If the fan just whirls around and you feel no increased air flow fan clutch is gone.
To test the water pump output firmly compress the top water hose going to the radiator (careful, it's hot), if it expands you have coolant flow. If it doesn't you most likely have a stuck thermostat.
Sorry, don't have enough experience on Aeroheads, but these guys do know what they're talking about.
Good Luck!!
Last edited by aero92; Jan 26, 2006 at 04:51 PM. Reason: left out text
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This may be a total coincidence, but, my new (2 day old) 95 4.0 AWD was doing something very like that. My temperature guage was swinging from below the N in normal all the way over to the L in a matter of seconds, then, it would swing back. It seemed to swing to the hot end when the AS was pointed UPHILL (even at a stop sign). Yesterday, I SEAFOAMed (is that a verb) the engine {per decarbonizing instructions by members on this sight). I took the AS out onto the highway for about an hour of 70+ driving. Not only is my engine smoother, but, the temp guage readings are now stable and what I would expect to see. I don't know if it was the Decarbonizing or the hour of highway driving, but, the temprature fluctuations are gone. Hope this helps. chad
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