My hot coolant light comes on & the needle goes to hot & then goes back again constantly. I replaced the radiator, thermostat, and water pump. What else can be the problem?
You may have air pockets in your cooling system. Try parking the car facing up hill to help the air pockets work their way out. This link is for Supra's but it applies to most cars --- http://www.supras.com/06/techcenter/display.php?QID=22
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