1998 Mustang Convertible temp gauge maxing


New Member
Mar 20, 2019
Saint Clair Shores, Michigan
Owning and driving for a year and a half. No problemd. All guages normal. In garage for dec and January. Need to drive a few miles since the wife had other car. Within 2 miles temp gauge maxed out. No steam. Drove 1 mile to destination. On way home stopped at Valvoline for an oil change. Topped off radiator fluid. On the way home gauge maxed out again within 1 mile
Put in the garage and haven't driven since other than starting every few weeks. Radiator, a/c all new within last year
. looking for a possible solution before I take to my mechanic.
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SN Certified Technician
Aug 14, 2009
Houston Texas
Just wondering. Have you performed a visual inspection looking for rodent activity? Smell anything under the hood?

Note a bad idea to perform a visual inspection of the engine coolant temperature sensor (ECT) electrical connector. Look for bent/pushed/corroded pins.

Also note that the V6 is very bad about trapping air inside the cooling jacket. There is a specific procedure to bleed the air from the coolant. Would you do that or take it to a mechanic?

V6 coolant refilling procedure
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B U R P the V6.... (94-95 at least)

in the center of the engine is a white ceramic looking ring that has a bolt on top. That is where it has to be burped at.

1. remove the bolt
2. fill the coolant until it comes out the hole
3. replace bolt

on these you can not just add coolant like other cars, you will have to do this procedure each time or that temp gauge will peg.

ALSO, if someone has installed a thermostat that will lock in open once the car overheats, you wont get it to heat up again until you pull the tstat and unlock it or replace it.

1990 5.0 LX

Apr 11, 2019
Ben Lomond, CA
Is the car actually overheating? Might be that voltage is leaking to the gauge causing the needle to deflect upwards. Happens on my '90 when the headlights are on. Suggest you determine what the actual temperature of the radiator is.