94 Taurus Fluctuating Temperature Gauge.

Tiny
RACINRAY
  • MEMBER
  • 1994 FORD TAURUS
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 102,000 MILES
I have a 1994 Ford Taurus GL with the 3.8 liter engine and 100,000 miles. I recently replaced the radiator due to a crack in the side tank and had the mechanic replace the t-stat at the same time. The motor was never overheated. One month after the replacements, the temp gauge on the dashboard started to fluctuate. In the morning or just when it is cold and driven for about 3 miles the needle would react normally and then begin to climb almost into the red. (Makes it to the vertical line on the hot side of the gauge) The engine does not seem to be overheating at this point. No heat in the cabin. The electric fan turns on and after about 2 minutes the needle drops down to midway or sometimes lower and heat is felt in the cabin. Then the cycle begins again. As the needle rises, I loose heat, fan turns on, needle lowers and heat is produced. This will happen for about 15-20 minutes or about 10 miles then suddenly everything is working properly. Great heat and the needle is in the normal operating range and steady. I had the mechanic re-replace the t-stat thinking the "new one" went bad. Same results. Assured that all the air is purged out of the system and the coolant is full. When cold, I notice I can add about 3 cups of coolant but each time I do this, the next time I check the reservoir when cooled down, it is a little fuller so I am assuming that while cooling down the freeze in the reservoir is not being drawn back into the system to maintain it's fullness. I have checked the water pump and it is dry and solid. No leaks on the ground under the car and the heater core seems fine as well due to the lack of wetness on the passenger floorboard normally associated with a leaking heater core. The system also is holding pressure for hours. Today I replaced the threaded in, 1" nut size "Coolant Temperature Sending Unit" which is located on top of the t-stat housing. This sensor has 2 wires going into it's plug, Light Green/Red and Gray/Red. I still have the same problem. What else can be causing this issue? I am a mechanic myself and am stumped. Please help if you can. Thank you for your time.

Ray
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Wednesday, April 6th, 2011 AT 11:22 PM

5 Replies

Tiny
PLATINUMHYUNDAITECH
  • MEMBER
Sorry to say it but these were known to have headgasket problems and it sure sounds like thats what is. You should have this tested for head gasket leaks
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Wednesday, April 6th, 2011 AT 11:47 PM
Tiny
CJ MEDEVAC
  • EXPERT
I've had a similar experience with my Dads '86 T-Bird. Had radiator vatted, We changed the stat 3 times and had the up and down temp too. He called me with the bad news (for the 3rd time), So I got a 4th one and drove 30 miles to his house to see if I could do something (We had already tested the previous 2 in boiling water) I had changed his sender, and we knew the radiator juice was mixed 70% Coolant 30% water. We ALWAYS MIX it in ju. Gs perfectly and then pour it in (always remains the perfect mix no matter what, doing it that way), Put 4th stat in--No more problem! I got the 4th stat in the town I'm in, The closest parts house to me at the time was NAPA, this was a different brand than the 1st 3. The only thing you have that he did not is Electric Fans, Could it maybe be a bad Coolant Temp switch (or whatever you call it, that turns your fans on) As you can tell Imma Jeep CJ guy, and do not know your rig well. As for the radiator juice loss, As your 1st response suggested, bad head gasket and you're burning it thru the cylinders, or maybe the up and down temp is overflowing it out. Let us know your fate, looks like the Site may be called 2bikepros if fuel keeps going up!---The Medic
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Thursday, April 7th, 2011 AT 12:48 AM
Tiny
RACINRAY
  • MEMBER
Thanks for the replies! One thing I forgot to mention which seems like now it may be important is that when I first fire her up, I have a lifter tick and a miss in the engine. As the engine warms up, say after about 2-3 minutes the tick disappears and the engine smooths out and stays like that until the next time I start her up from being cold. I'm thinking you may be right about that head gasket, but I don't see freeze in the oil, (no milky dipstick) and I'm not blowing any white smoke?
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Thursday, April 7th, 2011 AT 1:34 AM
Tiny
CJ MEDEVAC
  • EXPERT
Maybe its a really slight leak into the combustion chamber(s) not into the water jacket. Pulling the spark plugs and comparing them might show one (or more) looking a lot cleaner looking than the rest. Might give insight as to which had might need attention. This happened to "Willy", my 1946 Willys Jeep. I did not catch it till it was too late, it caused "Detonation" in #4 cylinder. This escalated into the top piston ring being "zapped" in two, an inch from the "Gap", the one inch piece somehow plowed thru the top of piston (my cylinder wall was spared!) I suddenly heard a Tapping, that would not go away (I have solid lifters and no rocker arms, He's a flathead 4 cylinder, Set up is similar to a Push lawn mower engine) The 1 inch piece of ring was barely tapping the inside of the head. While I was in there, I put new rod bearings in, had to buy a full set of rings and pistons. Put them in too. And a head gasket. Will show you some pics while it's going back together. I have not taken pics of the Detonated Piston (really pitted, and a hole in the edge caused by the ring segment) I still have them, just never took the pics yet! You can see the difference in the color of the combustion chamber on the bottom of the head (#4) See at the end. Whaccu think Racinray? I do not know 100%, But the "Ticking" may not be related in any way to the radiator juice loss. When that problem occurs in one I'm messing with, it's more than likely the Tappet (hydraulic lifter) is not sealing properly due to deposits etc in/ on it (its a complicated little hydraulic jack-like thingee, that oil pressure makes it "take up the wear or slack" in the valve train, every time it lifts up) Something that may make it stop, is to substitute 1qt. Of motor oil for 1qt. Of MARVEL MYSTERY OIL, next time you change your oil, it will break down and clean crap from the internals of your engine. Most parts stores have it, was used during WWII by the military---The Medic
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Thursday, April 7th, 2011 AT 2:35 AM
Tiny
CJ MEDEVAC
  • EXPERT
Just been making my rounds, showing my face a different locations, as to stay in good with people I depend on. Last stop was the transmission/ minor repairs shop. Chet just had finished a 2000 Cherokee. Problem was similar to yours--hard to diagnose. The fans would be on, to cool the radiator, whenever he was-a-diagnosing. He finally caught them not working, out of sheer luck. He had been concentrating on Fluid Loss, as Owner said it's Symptom was. Turns out fluid loss was not a head gasket problem, but it was boiling out. Boiling out, when the cooling fans were not operating. He said they came on every time he drove the vehicle. He could not make it Fluctuate in temp as described by the owner. BOTTOM LINE!The COOLING FAN RELAY WOULD NOT "MAKE" AFTER EXTENDED DRIVING. He showed me the relay, opened up, the little points or contacts were sorta burned, and were intermittently working. He said the 2nd hardest thinng was locating the CHEROKEE's RELAY. It was seen by removing the battery tray, and "Got To" by removing the passenger headlight.I hope yours is EZer to access than his. Regardless here's a cooling fan diagram that might help you now. Or even later! ----Your Turn--Good news only!--The Medic
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Thursday, April 7th, 2011 AT 7:57 PM

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