1971 Lemans coolant boiling
Check the thermostat, might be stuck closed.
Make sure you have 50/50 coolant and water. Plain water boils at a much lower temperature. If this and Tom's advice does not work then check compression to make sure you don't have a leaking head gasket.
Also check your ignition timing. If it's retarded (late) it will cause the engine to run hot and possibly boil over when shut off. HTH. - Jim
Looking for a Used Le Mans in your area?
CarGurus has 19 nationwide Le Mans listings and the tools to find you a great deal.
Search Pontiac Le Mans Questions
Pontiac Le Mans Experts
Related Models For Sale