My 98 626 V6 overheats when I'm in stop and go traffic or idling. It's fine when I'm running at highway speeds.

I'm guessing that it's something with the fan or maybe a thermostat?

What other symptoms could I look at to find out what it is? I usually have AutoZone read codes for me on cars but the engine light isn't on so I can't in this case.

Any thoughts would be helpful!
Thanks!

 

Sounds much more like a fan concern than a thermostat. If fan is not working then you would overheat at idle with no airflow to cool the radiator but would be ok on freeway since you have plenty of air now moving thru radiator. When it starts to overheat, open the hood and look to see if the fan(s), are running. Turn on the a/c and see if they will work then. If fans are running but is still overheating, make sure there is not restirction to airflow in front of condenser or radiator. If all ok, then unplug the fan so it will not run and place your hand on the engine side of radiator from top to bottom. Should be nice and hot all the way down. If not you probably have a restricted raditor in the area of your main cooling fan. If fan is not coming of when starts to get hot then you will be looking at a bad fan, thermoswitch, fuse, or relay. Let me know what you find out from observing the fans.

 

My 1993, 929 was overheating the same as your 626. It would cool though when idling. I replaced the fan clutch thinking that it was kicking out on the highway. Did not fix. My radiator was less than 2 years old, but had it checked and it was really clogged. I had purchased a bad one from the start. Radiator shop warrantied it and gave me a new one. Car running fine now.

 

you problem is hole broke, radiator dirty, you can bypass the control of fan and you conection the fan radiator direct to battery and you run the car for long time, too the gasket cylindre head bad