Temperature gauge shows HIGH!

[NOMORECHEVY]

My 1996 Mustang GT4.6 has a new water pump and fresh coolant but the temperature needle points toward high while driving the car. The needle stays in the "safe range" but always is 3/4 or more toward HIGH. I checked my friend's same model Mustang and while driving it, the needle always stays in the midle or lower while in the "safe" range of the gauge. Does anybody knows why my gauge reads higher? Just wondering. The actual millage in my car is less than 78,000.

 

[timeless2]

Have you tested the thermostat? How long does it take to warm up? How many miles do you have?

 

[RedBullitt]

check the thermostat, it might be staying closed and generally screwing up.

 

[Jinx]

2 other things to consider also:

1 coolant/water ratio
2 air in the system

 

[timeless2]

testing the thermostat:

1. Pick up a new one (you'll likely need it anyway and they are cheap).

2. Pick up a gasket or use hi-temp RTV sealant for use on the re-install of the old thermostat or the new one.

3. Remove your current thermostat (further known as "stat").

4. Boil some water on the stove with the thermostat in it from the beginning. Monitor the temp with a candy thermometer, etc to see when the button in the center of the thermostat drops to let the coolant flow (when it would be installed in the car). If you have a 195* stat, it should open within a 5 to 8 degree tolerance and close after that range, hence measuring with a thermometer.

5. Place some ice (carefully and slowly!!!!) in the boiling pan to get the water temp to drop and observe the stat closing back up as the temp drops.

6. If your stat does not act like a temperature actuated valve, it's shot. Coming on 10 years of constantly opening and closing, it could be done for.

7. If it's shot, use the new one you bought (from step 1) to replace it. Seal up everything, start it and check for leaks.

8. After one good heat up/cool down cycle, check your coolant level and add as necessary, as you probably spilled some when removing the stat. Use a 50/50 mix of coolant and water.

9. Monitor your hot/cold cycle for a bit while idling and do another road test.

10. If the problem still persists, you might have blockage elsewhere, a faulty head gasket (check your oil for discoloration and increased level), or a major air bubble somewhere in the system. It wouldn't hurt to also get a new radiator cap, as pressure is a key component in a cooling system.

Hope this helps.

 

[sgarlic]

If it's always been like that: needle not seated properly. You have white faced gauges? If so the needle probably was placed back on incorrectly.

If it were the thermostat stuck closed (which it isn't,) you'd have an overheating condition, not just running a little bit hot.

If I recall correctly, the gauges even in the 96-98 were dummy gauges just like the later models.. you're probably running at the right temp.

I wouldn't worry about it unless you boil over, or it gets worse.

 

[timeless2]

If it's always been like that: needle not seated properly. You have white faced gauges? If so the needle probably was placed back on incorrectly.

If it were the thermostat stuck closed (which it isn't,) you'd have an overheating condition, not just running a little bit hot.

If I recall correctly, the gauges even in the 96-98 were dummy gauges just like the later models.. you're probably running at the right temp.

I wouldn't worry about it unless you boil over, or it gets worse.

Running a bit hot would indicate the stat only partially opening/closing, ie, not letting the water have time enough to cool properly, but time enough to prevent overheating. I've seen it before on other engines. Usually, it is a precursor event to overheating.

 

[sgarlic]

The problem with that theory is that he has a dummy gauge. If he were running a few degrees hotter because of a partially stuck t-stat, he would never know unless he overheated. The dummy needle won't move past the normal operating temperature, unless it's in an actual overheating condition.