Radiator & Overheating Questions:

Note this on thermostats;  The only thing it does is get the engine up to the specified coolant temperature faster so that in the winter your heater will provide heat, a 180 degree thermostat stays closed until the coolant heats up to 180 degrees, once it has opened its job is done.  If your engine in the summer wants to run 200 degrees it will do so whether you have a 160 or 180 or 195 thermostat in it.  If you use a 160 thermostat in winter you won’t get much heat from your heater.

Note this on gauges; you cannot rely on your 40 year old stock gauge, so do not base questions on your system on the gauge alone.  If possible install a good aftermarket gauge or have your original restored and you will feel a lot more confident about the condition of your coolant.

Check your cap first and be sure that the seal is good and that the pressure release is not frozen. It is normal in any car, for engine coolant temperature to increase when stopped in traffic regardless of cooling system size.  The first question to be answered is:  Are you putting coolant on the ground ?  Regardless of what your temp gage says, if you are not actually loosing coolant out the overflow tube, and your cap is working as designed, you probably don’t have a problem.  If your system will hold a consistent temperature below the boiling point that your particular system is set up for, even if it seems too hot to you or your gauge, you are probably OK and need not worry.  The temperature of coolant your system can hold is controlled by the radiator cap you are using.  The original radiator in your classic used a 7 lb. Cap, so the boiling point of these systems (about 230 degrees) is low by today’s standard as most vehicles today use a 15 lb. Cap (about 250 degree).  Normal engine operating temperature in summer without AC (if you have it) running is 190 to 200 degrees for most engines, in traffic this would go up 10 degrees or so, with AC on this could go to 220 or more.  If your system will hold this temp in traffic without going higher it is functioning good and needs no further attention.  You can raise the boiling point by putting a higher pressure cap on the radiator, up to 13 lbs. on a repo rad that has the original style tank,  this is not a good idea on an original (40 year old ) radiator as the tank sides could get bulged out permanently by the higher pressures generated if the engine gets close to overheating.  If the parts in your current system are functioning correctly as noted above but your radiator cannot hold coolant in summer traffic, then you need to upgrade it.

To Figure Your Engine Coolant Boiling Point:

 2. Add 3° for each pound of your radiator cap, so… if you have a 7 LB cap that would be 21°.

 3. Add that (21°) to the 212 which makes a Boil over point of 233°.  With a 13 LB cap it would be 251°