1999 Temp Guage on Hot

[aztec]

Hello, new to this forum and I'm hoping someone can help with a problem. Our 1999 Miata temp needle climbed to hot the other day. Granted it's hot here in SoCal's San Fernando Valley, and the needle climbed when the AC was turned on climbing a grade. But the needle continued to stay hot after the AC was turned off. Car was then parked for the balance of the day, and driving home that night the needle stayed in the normal middle position for the 35 mile trip.

We took it in two days ago, the thermostat was found to be stuck and replaced, new coolant, etc. But yesterday, after leaving the shop, the needle shot up again, so this time I had Auto Club tow it back to my mechanic.

Can anyone explain what might be happening? Our shop says the water pump is fine, and hoses are intact. Any help would be appreciated. Thank you in advance.

 

[erik111]

You are going to want to repost this in the MX5 Miata section, since this is the Mazda 5 mini-mini-van section.

 

[Robotazky]

Find a way to take the temp of a part of the cooling system, like a coolant hose, when it's normal and compare it to when it's hot. This will allow you to tell if the gauge or sending unit is malfunctioning.

 

[flcruising]

Stuck (closed) thermostatic is definetely not a good thing, but did they check whether the radiator fan(s) are operating?

 

[Robotazky]

Stuck (closed) thermostatic is definetely not a good thing, but did they check whether the radiator fan(s) are operating?

LOL, uh yeah, good question. Didn't even think about that. You should be able to turn the A/C on and drive up the hills until it starts overheating, stop, get out and check for the fan(s) running.