Triumph Repair: 79 Spitfire overheating, engine temp, headgasket

Question
We just bought a 1979 Spitfire last night & had overheating issues on the drive home. We test drove it in 100+ degree heat with no overheating issues. Drove the car home last night, and after about 20 minutes it overheated & the engine died. The radiator was practically empty, so we let it cool down & filled it with water - all we had with us. Car restarted fine, but had the same trouble about another 20 minutes down the road. There is no visable leak of any coolant & the car restarts fine. The engine temp gauge never got above the 3/4 mark. We are replacing the thermostat today. If that doesn't solve the problem, what would be our next steps to troubleshoot the problem?

Thanks for your help,
Ann

Answer
Ann,

If the radiator is empty then there is a leak.  It's either an external leak, from the radiator, from the water pump, from a hose, from the heater core.

Otherwise it's an internal leak via the headgasket.

Have you checked the oil level?  Does the engine oil look normal or is it milky?

Otherwise the water could be leaking into a cylinder and it's being passed out the exhaust.

Finding and fixing the source of the leak should stop the overheating problem.


Cheers,

Jim