Make sure you main fan is clutching properly. You should be able to hear it kicking in. If not, then the clutch is shot and will need to be replaced. If the main fan is working, I would replace the radiator. Hell, replace it anyway. You will notice the difference.

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Jeff Lawrence
1989 300e
2000 Dodge Grand Caravan SE
No matter what you fix, there will always be something else to fix..
"Warranty" is just another way of postponing the inevitable.