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Temperature guage moves up and down whild driving - 96 GL

06-27-2006, 03:32 PM
My '96 GL temp gauge moves from about 3/8 to 1/2 when driving and then engine is fully warmed up. It almost never goes past 1/2 (if it does it goes to 5/8 and then comes back down). The 3/8 to 1/2 cycle repeats ever 30 sec to 1 minute.

Is this a serious problem or can it be ignored? What's going on?

06-27-2006, 05:30 PM
First thing I would do is find the sensor for your gauge, remove the connector, make sure it's clean, then recheck operation, hopefully that will do it.. easy things first...

06-27-2006, 05:49 PM
So you're saying that as the car warms up, the temp guage moves to the halfway point (middle of NORMAL) and floats around that point? That seems about right. If your cooling fan is working properly, the coolant temperature should not go much over the middle of the guage.

If the fluctuation is as often as you describe, that would seem a little rapid though. Does it seem to correlate to the cycling of the cooling fan?

If you check the Coolant Temperature Sender connection and it seems clean and tight, then check for an air bubble in the cooling system once it cools.

Did this just start to occur following some maintenance on your car?


06-28-2006, 01:12 AM
Thanks for the responses. I would like to check the temperature sensor. Where is it located?

The car has just had freeze plugs replaced since it has had a coolant leak. However the fluctuating temp gauge has been happening for a few months. It almost seems like the cooling system isn't keeping up, and then it catches up and overcompensates, and the cycle continues.

I also noticed that when driving slow (like in a parking lot) after a long drive (long enough to reach full operating temp) the temperature gauge indicates a shightly higher than 1/2 way reading.

Is there anything else I can check besides the temp sensor? I don't think there is air in the system since it was just refilled, but i'd like to check that do i do that?

I don't see how it could be a fan issue because it still fluctuates at freeway speeds...and at that speed wouldn't the wind from going 60+ MPH be way greater than the fan's effect?

Sometimes the temp does go above normal (ever so slightly above 1/2) except in the parking lot scenario where it is at 5/8.

Thanks in advance for your help!

06-28-2006, 08:34 AM
check your thermosatat. It could be sticking. I don't think they are that expensive so by checking it I am saying to replace it.

06-28-2006, 11:14 AM
Is the thermostat the same as the temperature sensor? Where is it (are they) located?

06-28-2006, 12:40 PM
If you just had the system serviced, you are more likely to have air in the system than if nothing had been touched. When the system is drained, even part way, the space that used to be occupied by coolant will now be occupied by air. When the system is refilled, the coolant needs to displace the air, but if the air gets trapped, you now have an air pocket that can cause what you describe. Typically trapped air will cause a more drastic swing of the temp guage though. Anyway, something to look at. Some Taurii use a "jiggle valve" in the thermostat to allow the air to escape. The valve needs to be oriented properly when the thermostat is replaced (12 o'clock position). Other Taurii will have a bleed valve located in the system, but I'm not sure which your car uses and where it's located.

If you have the jiggle valve in the thermostat housing and it's properly oriented, the system should bleed the air on its own after some time. If you have a bleed valve, it should be located at the highest point of the cooling system. I'm not sure what the factory-recommended procedure is. I expect you could open the valve though and start the car. You should also have the pressure cap removed. Let it run and get up to operating temperature. As the coolant starts to expand, it will start to run out of the bleed valve after it forces all the trapped air out. While heating up, monitor the coolant level in the reservoir and make sure it doesn't get below the recommended level. Once you notice coolant coming out of the valve, you should then close the valve and turn off the engine. Replace the pressure cap. Again, I don't guarantee this to be the recommended procedure. If you want to find the correct process, I suggest you purchase a service manual for your car. I'll try to find time tonight to pull out my service manual and get more specifics for the '96.

The sensor and sender will usually be located near the thermostat housing. They will often be small brass threaded plugs with either one or two wires connected to them. The connection will usually be plastic.


06-29-2006, 11:59 AM
Per the 1996 Ford service manual:

Fill cooling system as follows:

Install all cooling system hoses that were removed.
Check all hose clamps for proper tightness.
Raise vehicle on hoist.
Ensure radiator draincock is closed.
Install splash shield onto front of front sub-frame and body. Tighten retaining screws securely.
Lower vehicle. CAUTION: Use extreme care to keep coolant mixture off of the drive belt (8620) and pulleys. If needed, remove drive belt and rinse with clear water. Clean pulleys and install drive belt. Belt squeal and early drive belt fatigue will occur otherwise.
Add coolant mixture into fill neck on radiator coolant recovery reservoir (8A080) until coolant reaches top of cold fill range mark on radiator coolant recovery reservoir.
Reinstall pressure relief cap to radiator coolant recovery reservoir.
Bleed cooling system as follows:

Select maximum heater temperature and blower motor speed settings. Position control to discharge air at A/C vents in instrument panel (04320).
Start engine and allow to idle. While engine is idling, feel for hot air at A/C vents. CAUTION: If air discharge remains cool and engine coolant temperature gauge does not move, engine coolant level is low in engine and must be filled. Stop engine, allow to cool and fill cooling system as outlined.
Start engine and allow to idle until normal operating temperature is reached. Hot air should discharge from A/C vents. The engine coolant temperature gauge should maintain a stabilized reading to within the NORMAL range and the upper radiator hose (8260) should feel hot to the touch.
Shut engine off and allow to cool.
Check engine for coolant leaks.
NOTE: When engine coolant level indicator flashes, approximately 0.946-1.416 liter (1-1.5 qts.) of coolant mixture can be added to the radiator coolant recovery reservoir after a proper engine coolant system refill.
Check engine coolant level in radiator coolant recovery reservoir and fill as necessary.

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