Ok. The overheating is an intermittent problem. I may make 2-3 trips (5-10 miles) and no overheating. Then, I may make a 1-2 mile trip and it overheats. To make it even weirder, if I turn on the heater the temperature drops from med-high to COOL in about 3-5 seconds.

I have replaced the thermostat, the water pump is new when I replaced timing belt less than 5,000 miles ago.

No evidence of coolant in oil, no smell of coolant in the exhaust. Car runs beautiful, just HOT intermittently.

Coolant appears to be flowing properly thru the radiator.

Ideas? Thoughts? I appreciate ANY and all help.

Thanks, Dave

2 Answers 2


Are your rad fans kicking on? When you travel the long distances air might follow faster through your rad and cool better, while on short slow trips this doesn’t happen. For the heat, that’s expected because the cabin heat relies on coolant heat, and when you turn the heat on it draws from the coolant making the cabin hotter and the coolant cooler

  • in that short of a period? I have NEVER seen it drop THAT fast. I have always seen a slow decrease in my other cars. And if you leave the heat on, the temperature goes back up. Turn it off, it goes back up. Wait 1-2 minutes, it drops it drastically again. I just wondered if it had a temp sensor near the heater hoses that maybe wasn't working correctly. Commented Sep 24, 2017 at 17:14
  • Well you could check if there’s anything in the overflow to diagnose a temp sensor going bad, if it’s getting really hot. Commented Sep 24, 2017 at 17:23

Time to replace the radiator. Coolant might be flowing, but you likely have sections that are clogged. You can verify this possibility by shining a cheap inferred thermometer over the entire surface of the radiator when she overheats. You will likely find cold spots on the radiator (a good radiator will be the same temperature throughout).

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