QuestionMy '75 Spit all of a sudden started running hotter than normal while driving. I read elsewhere to check the voltage across the temp gage to make sure there is not a voltage issue - is there a quick way to check that the water pump is circulating coolant without pulling it? I replaced the thermostat with no improvement in cooling.
AnswerYou should be able to pull the radiator cap, and look inside the radiator when running;
When the thermostat is closed, the fluid will be stagnant.
when the thermostat opens, you'll get a surge in the radiator, and then the level will drop, and you will see turbulence in the coolant as it circulates.
Unlikely that is the problem, thought. When water pumps fail, they either make noise, sieze, or leak. Rarely does the impeller come free of the shaft.
Check for water in the oil (oil drops on the dipstick, peanut butter under the oil fill cap), or some other source of coolant leak (hose clamps, etc)
You can also use the heater core when driving; when you see the temp rise, open the heater in the car to max, and see if that lowers the engine temp; it should, as the heater is another mini-radiator.
Check some of my other responses; I've put a few links out to web sites for others that have had spit temp problems, and what they have done.
On the voltage issue, there is a voltage regulator on the back of the speedo that lowers the voltage to about 10v for the electric gauges, 10V is max temp on the gauge.
