BIG TOM Posted January 15, 2015 Share #1 Posted January 15, 2015 Ok I need help from all the motor heads.. I am at my wits end...I have a 2004 f 150 ford heritage , 6 cylinder 4x4 with a 5 speed in it (117,000 MILES ON IT)....my temperature gauge reads normal for a while(20,30 miles) then will go to cold, then back to normal, then will fluctuate back and forth about every 8 miles from normal to cold....I DO NOT lose any heat and the truck seems to run normal...I had a new thermostat installed about 2 weeks ago and all seemed well until today when it started doing it again.... I drive 30 miles to work. It did it once or twice today on the way to work but on the way home it did it about 10 times....I don't know enough about these things and an a little nervous driving it.. is there a sensor I should be looking for?.. Is it safe to drive? will I damage something driving it back and forth to work? Thank you for the help in advance.... Link to comment Share on other sites More sharing options...
gmarshall Posted January 15, 2015 Share #2 Posted January 15, 2015 Are you losing antifreeze? I had an 03 f150 with the 4.7litre 8 that started doing things like that. It also overheated. After the dealer replaced two spark plug power packs, it ultimately was one of the head gaskets that were going. $3000 later I traded it in. hope your problem is something else. Link to comment Share on other sites More sharing options...
Oldodge Posted January 15, 2015 Share #3 Posted January 15, 2015 My first thought would be the temperature sensor (sending unit) or the wire that plugs into it. Link to comment Share on other sites More sharing options...
cowpuc Posted January 15, 2015 Share #4 Posted January 15, 2015 While it is entirely possible that you have another bad thermostat (just cause its new doesnt mean its not sticking again) its also possible that you simply have a bad connection on the sending unit for tempt guage or a bad sending unit itself... That sending unit should be fairly easily identifiable by its location - probably near the area of where the thermostat is housed or somewhere on the coolant system.. Most are just a single wire little post sticking up.. Find that puppy and check the wire connector at the sending unit terminal first.. It is possible too that you have something happening like Gmarshall is talking about - good Lord lets hope not!! If you have a head gasket leaking into the combustion chamber - most of the time you will actually smell antifreeze in the exhaust and the exhaust will be noticeably foggy,, if its going into the oil - you will get muddy looking oil - usually noticable around the oil fill cap or on the dip stick - possibly in the coolant itself.. Not sure if your truck has a radiator with a cap on it? Some of this new stuff is sealed.. If it does, you should be able to remove the cap (CAREFUL IF ITS HOT!!) and run the truck with the cap off while keeping an eye on the coolant in the rad and the gauge.. You should be able to see the guage climb while the thermostat is closed and the fluid is not moving.. When it gets to its normal op tempt the thermostat should open - you should see coolant being moved thru the rad and the guage should drop - as the coolant cools off - the thermostat should close and the coolant should stop moving again and the guage should climb again... Link to comment Share on other sites More sharing options...
cowpuc Posted January 15, 2015 Share #5 Posted January 15, 2015 My first thought would be the temperature sensor (sending unit) or the wire that plugs into it. I gotta learn to type faster!! Link to comment Share on other sites More sharing options...
BIG TOM Posted January 15, 2015 Author Share #6 Posted January 15, 2015 I am not loosing any coolant nor is the exhaust foggy, but that's hard to tell because its been really cold out. its not overheating...the gauge goes to cold then back up to normal ?????? Link to comment Share on other sites More sharing options...
wrnchjox Posted January 15, 2015 Share #7 Posted January 15, 2015 should be a faulty coolant temp sensor,that sensor should be near the thermostat housing,generally one wire for gauge sensor and in your best interest to get OEM sensor as has been my expirence that the aftermarket ones dont seem to last on the ugly blue ovals. Link to comment Share on other sites More sharing options...
rbig1 Posted January 15, 2015 Share #8 Posted January 15, 2015 is the other gauges moving around. There is a resister on dash that might be getting weak. Makes other gauges change at same time but not as bad. Or did they pinch the wire in housing. Link to comment Share on other sites More sharing options...
BIG TOM Posted January 15, 2015 Author Share #9 Posted January 15, 2015 THE ODOMETER cuts on and off, but its been doing that for a couple of years...that's a loose wire. I don't think they are related Link to comment Share on other sites More sharing options...
midnightventure Posted January 15, 2015 Share #10 Posted January 15, 2015 I would hook a good code scanning tool to it and see what it says. A good one can read the temperature and basically bypasses the built in gauge. My 1995 Trans Am always shows cool but when I hook up my scan tool it shows about 195 degrees like it should be. At that point I quit worrying about it. If it ever jumps up from where it normally is I will take a look at it. Link to comment Share on other sites More sharing options...
billmac Posted January 15, 2015 Share #11 Posted January 15, 2015 Sounds like they unplugged the sensor plug and it didn't snap back on. being loose will give that kind of reading. Link to comment Share on other sites More sharing options...
bongobobny Posted January 15, 2015 Share #12 Posted January 15, 2015 Hope it's just a loose wire or bad gauge Tom, because the symptoms you describe, if it really is doing that temperature wise, sounds like a blown head gasket... Link to comment Share on other sites More sharing options...
Condor Posted January 15, 2015 Share #13 Posted January 15, 2015 Ok I need help from all the motor heads.. I am at my wits end...I have a 2004 f 150 ford heritage , 6 cylinder 4x4 with a 5 speed in it (117,000 MILES ON IT)....my temperature gauge reads normal for a while(20,30 miles) then will go to cold, then back to normal, then will fluctuate back and forth about every 8 miles from normal to cold....I DO NOT lose any heat and the truck seems to run normal...I had a new thermostat installed about 2 weeks ago and all seemed well until today when it started doing it again.... I drive 30 miles to work. It did it once or twice today on the way to work but on the way home it did it about 10 times....I don't know enough about these things and an a little nervous driving it.. is there a sensor I should be looking for?.. Is it safe to drive? will I damage something driving it back and forth to work? Thank you for the help in advance.... Sounds like you have a loose wire on your sensor.... Link to comment Share on other sites More sharing options...
ricksbike Posted January 16, 2015 Share #14 Posted January 16, 2015 On any 04 vehicle if the temp guage,sensor or wiring were faulty it would set a check engine light,I would guess at a bad new thermostat or an air bubble in the cooling system. Link to comment Share on other sites More sharing options...
Gray Ghost Posted January 16, 2015 Share #15 Posted January 16, 2015 Just a note on scan tools. There is an app called torque for smartphones that works with a bluetooth device ELM327 that plugs into the ECM port ( ) gives you the ability to clear codes also on OBDII. Link to comment Share on other sites More sharing options...
frankd Posted January 16, 2015 Share #16 Posted January 16, 2015 Most vehicles of this age feed the temperature sensor signal into the engine computer, and the computer has an output that connected to the temperature gauge. Seeing that your odometer also stops working, I'd suspect a problem in your dashboard itself. Try lightly taping the dashboard the next time one of them takes a siesta. Also you could try 'GOOGLING' the problem (search for 2004 F150 temperature gauge" and see what you come up withl Link to comment Share on other sites More sharing options...
dfitzbiz Posted January 16, 2015 Share #17 Posted January 16, 2015 Could be air in the system. Chevy 3.8L V6 has a vent plug to clear the air out of the system I don't know about the Ford. Take a look at this site Air in cooling system - F150online Forums Good Luck! Link to comment Share on other sites More sharing options...
Brenner Posted January 16, 2015 Share #18 Posted January 16, 2015 BIGTOM, In my opinion you have an electrical concern whether it be a connection to the temp sensor, or gauge cluster concern. Because it goes from operating temp to cold and back in abrupt movements this seems possible. The guys are correct when they mention air in the system is possible but usually there is more symptoms as loss of coolant whether consumed or leaked or pressure in the cooling system when a head gasket is due but usually with a head gasket you have an overheat symptom. What I at this point without see you problem am thinking is that you are having a cluster issue as in the years I have spent in the auto industry I have seen this happen more times than I count on my hands. You mention the odometer comes on and off and on some models I have seen this hand in hand with your problem. A lot of the newer vehicles no longer have a separate sensor for the cooling gauge and use the PCM (Powertrain Control Module) coolant signal as a reference through the CAN (Controller Area Network) system to operate the gauge assembly (Instrument Cluster). Companies have been doing this since roughly 2000 and this is more cost effective in production as this system uses less wires (less to have problems with), smaller gauge wires (size) and offers the ability to monitor systems (if problems can set diagnostic trouble codes). There is a self check function on these instrument clusters but I can't remember the proper sequence for your vehicle. Usually holding the odometer rest button while in trip function at a certain time and using the ignition. If we were closer I would be happy to lend a hand. The info I offer is based on the info I have been given and may or may not be accurate to your problem. If I were to see your vehicle first hand perhaps I would notice something not noticed or something another person may not think is related but in fact is. Just because x number of people say it is one thing does not make it so. Try not to fixate on their or my diagnosis as we have not seen it in person and just think of it as a possibility and rule them out one by one. Think outside the box as this has made me a strong electrical and drivability technician in the dealership. Good luck, if I can help feel free to contact me. Cheers Link to comment Share on other sites More sharing options...
Angelo Posted January 16, 2015 Share #19 Posted January 16, 2015 You have a sensor for the coolant temp for the PCM and one for the gauge on that truck. That system on yours is pretty simple, gauge and wiring>body control module>instrument cluster. I can count on one hand how many BCM's I ever replaced on trucks like yours and the instrument cluster is not as common a failure point as say the GM instrument clusters. Temp sending units on those were pretty common and they are cheap so I would start there. i would first make sure that there is no air in the system, that can make the gauge bounce around. Run the truck with the coolant tank cap off with the heat on high until the the system is up to full temperature for 15-20 minutes. Top off the coolant and then drive it and see if the problem is resolved. Check the connector at the temp sensor to make sure it's clean and not loose. If all else is clean and the system has been properly bled, replace the sensor and repeat the bleed procedure. Link to comment Share on other sites More sharing options...
steamer Posted January 17, 2015 Share #20 Posted January 17, 2015 OK, lets try the simple fix first. As mentioned previously, You probably have air in the system. This is very common when the cooling system is drained to replace the thermostat. Try removing the radiator cap and start the truck. Let it run until the temp comes up and the thermostat opens. you can tell it is open by watching the coolant inside the radiator, you should see it start to flow around inside the radiator. Shut it off and let it sit with the cap off for an hour or so. replace cap and drive it. If this doesn't work, buy a new truck. Link to comment Share on other sites More sharing options...
Flyinfool Posted January 17, 2015 Share #21 Posted January 17, 2015 OK, lets try the simple fix first. As mentioned previously, You probably have air in the system. This is very common when the cooling system is drained to replace the thermostat. Try removing the radiator cap and start the truck. Let it run until the temp comes up and the thermostat opens. you can tell it is open by watching the coolant inside the radiator, you should see it start to flow around inside the radiator. Shut it off and let it sit with the cap off for an hour or so. replace cap and drive it. If this doesn't work, buy a new truck. A Chevy....... Link to comment Share on other sites More sharing options...
billmac Posted January 18, 2015 Share #22 Posted January 18, 2015 Find the trouble yet? Link to comment Share on other sites More sharing options...
tankerman Posted January 18, 2015 Share #23 Posted January 18, 2015 To my very inexpert opinion it sounds like a loose wire somewhere in the sending circuit. Recommend you trace then check the wires for connectivity . Link to comment Share on other sites More sharing options...
BIG TOM Posted January 27, 2015 Author Share #24 Posted January 27, 2015 Find the trouble yet? Yep, had the radiator flushed, and an OEM thermostat installed . When my mechanic went to check the connection on the sensor, it snapped off in his hand. He had to drill and tap it to replace it....so far it seems to have taken care of the problem....he changed the oil and found no coolant in the oil ..he also did a compression test to make me feel better that there was no blown head gasket...total cost...$.221.00.. My mechanic only charges me 45.00 an hr. for labor cost... It beats $45,000.00 for a new truck... Link to comment Share on other sites More sharing options...
Yammer Dan Posted January 27, 2015 Share #25 Posted January 27, 2015 Connection on sensor. Take 30 seconds to prove me wrong before you start looking elsewhere. Link to comment Share on other sites More sharing options...
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