Abnormal Temperature Fluctuation
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Freshman User
Joined: Feb 2002
Posts: 29
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From: Dickinson, TX
Abnormal Temperature Fluctuation
'91 F-150 with 302, A/C, auto, and standard cooling.
I notice that the temp gauge fluctuates between just about the low-end of the scale to between the O and R in "NORMAL". Happens mostly when accelerating from a stop, easy or hard... but also happens when just driving.
Any thoughts as to what is causing this? The truck did not do this when I first bought it (used) at 67,000 miles. Has been doing it since about 72,000 miles. Has 95,000 today.
I have replaced the thermostat and have power flushed/refilled the cooling system.
-Mike
I notice that the temp gauge fluctuates between just about the low-end of the scale to between the O and R in "NORMAL". Happens mostly when accelerating from a stop, easy or hard... but also happens when just driving.
Any thoughts as to what is causing this? The truck did not do this when I first bought it (used) at 67,000 miles. Has been doing it since about 72,000 miles. Has 95,000 today.
I have replaced the thermostat and have power flushed/refilled the cooling system.
-Mike
Senior User
Joined: Jan 2001
Posts: 416
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Abnormal Temperature Fluctuation
I have a '93 F150cc w/5.0 5spd 4x4 and it does the same thing. It is almost like the thermostat is opening and closing to keep the temp at a constant level. I have never seen this happen in any other vehicle that I have owned. I wonder if it is a bad ground in the temp sender due to rust in the threads. I have had a similar problem with Ford oil pressure sending units. Taking it out and cleaning it and then re-instaling it cured the problem. It is too darned cold out to start messing with my coolant system right now though.
Senior User
Joined: Apr 2001
Posts: 223
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From: Canton, OH
Abnormal Temperature Fluctuation
My 96 I6 does the exact same thing. I hooked up my laptop to the ODBII to get a temp reading and at idle (gauge on the "NO" in normal) I was at 200 degrees with a 8 mo. old thermostat.
NJK
NJK
New User
Joined: Apr 2002
Posts: 10
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From: LAKE STEVENS USA
Abnormal Temperature Fluctuation
i have a simular problem my temperature fluctuates between "o" and "m" constantly while i'm driving and it started after the system was flushed and i'm not sure where to begin. i have a 1995 f150 351.
Elder User
Joined: Aug 2000
Posts: 763
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From: home
Abnormal Temperature Fluctuation
It does it on my 89 Bronco II with everthing new radiator,hoses,thermostat including rebuilt engine etc. Same on my 93 Aerostar with new hoses & thermostat & 92 F150 5.0. The 92 F 150 did not due it untill I replaced the water pump & flushed the system. Before it used to sit on N all the time. I think the thermostat was sticking partly open. Not sure what to do???? 
Freshman User
Joined: Dec 2000
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Abnormal Temperature Fluctuation
Hey Dmdcart. I have the same truck as you 95 F-150 351 and mine does the same fluctuation between O and M. Does not make a difference if it is towing a load or just cruising down the highway. I've just come to live with it but now I'm not sure what to think.
Has anyone installed a manual water temp gauage in their truck? This has been on my to do list but I haven't gotten around to it. Anyone have some advice on where to install the sensor for a manual guage? I heard one person on this site installed it in the line leading to the heater core. This makes sense to me, but I could be way off.
Thanks,
Joey
Has anyone installed a manual water temp gauage in their truck? This has been on my to do list but I haven't gotten around to it. Anyone have some advice on where to install the sensor for a manual guage? I heard one person on this site installed it in the line leading to the heater core. This makes sense to me, but I could be way off.
Thanks,
Joey
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New User
Joined: Apr 2002
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From: LAKE STEVENS USA
Abnormal Temperature Fluctuation
well mine does it wether i'm towing,running down the highway or sitting still....
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Posting Guru
Joined: Jan 2001
Posts: 2,358
Likes: 3
From: Nebraska
Abnormal Temperature Fluctuation
Mine does it too, along with my parents' '95 Taurus and '96 F-150. I didn't think it was a problem.
--------------
[font color="green"]1995 F-150 Supercab XLT longbed 4x4 302 M5OD [/font]31x10.50's
[font color="green"]1986 F-150 4x4 300 I6 NP435 [/font]Warn hubs, DeeZee bed caps, '96 XLT bench seat, new paint job
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[font color="green"]1995 F-150 Supercab XLT longbed 4x4 302 M5OD [/font]31x10.50's
[font color="green"]1986 F-150 4x4 300 I6 NP435 [/font]Warn hubs, DeeZee bed caps, '96 XLT bench seat, new paint job
Senior User
Joined: Jan 2001
Posts: 416
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Abnormal Temperature Fluctuation
My 93 F150 with the 5.0 does it too. When I pull the dipstick to check the engine oil when the motor is hot the dipstick is screamin' hot, at least I think it is. What is the normal temp for this engine to run at? What is the normal thermostat used, 180 or 192? I guess I will have to hook up a mechanical temp guage to find out what the actual temp is.
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