A failed vacuum advance can cause overheating as well. Although I think on a 1975 its vacuum retard? Not sure how that would affect engine temp?
When you refill for the winter . Put the fast idle cam on the first step to raise the idle speed . Then let it " burp " once or twice before putting the cap on while filling . THEN drop the idle speed . Good luck
The coolant temp sensor is on top of the intake, so changing it. doesn't really spill antifreeze(Apparently WRONG see Larry below). FYI. I am all 1968, so they didn't come with overflow, and the radiator isn't filled to full when cold. Sorry if I confused. Glad to hear your driving and on the right track.
Yes it would. The fluid level of coolant in the radiator is higher than the intake. Removing that sensor will cause a big spill until the level equalizes. When changing the sensor, you must drain the radiator until the level is below the top of the intake.
Kinda guessing the dash light didn't glow, because the engine never got hot enough. Further guessing that the dash light doesn't glow during starting, because something OTHER than the sensor (something in the bulb-test circuit) has failed--ignition switch, wire harness, etc. Testing the sensor itself will be difficult, as you'd have to get the thing REALLY HOT to get it to go from "open circuit" to "closed circuit". WHY would you change a working temp sensor? The new one is probably going to be a Communist bottom-feeder piece, lower quality than the one that's on there now. Sure, IF (big IF) the sensor has actually failed...you'd need to replace it. If it's still working, leave it the hell alone. I've never seen a vacuum retard on a Delco distributor. I've seen a retard/advance dual canister on a very few Fords.
Yea, you can't fully fill the system until the thermostat opens up. Doing a full drive cycle is one way but most refill cold up to the top. Then idle the motor until the thermostat opens up. The level in the should drop when the thermostat opens.
Ehhh. Depends on the thermostat, and it depends on how much of a hurry you're in. A Robertshaw-style thermostat has a tiny air vent stamped into the metal. Allows the air in the block and heads to escape into the upper radiator hose and then to the radiator. Or let the "full" cooling system settle overnight, the air will escape past the thermostat (slowly) and there'll be air in the radiator by morning. Some folks drill bigass holes in the thermostat flange, but that's kinda counterproductive. In most cases, it's a permanent and ill-advised "solution" to a temporary problem.
An option if you don’t want to add a gauge and want high temp warning before damage occurs is to install a temp sensor that lights up earlier than 250*. I had a failed thermostat cause an overheat and the light came on seconds before the coolant started dumping and seconds after the engine started running like crap. I put a 230* sensor in so it gives me enough warning to pull over and investigate before serious damage occurs. It adds a better margin of safety than the factory did, as when the light came on at 250* it was enough heat to kill the head gasket. I got a Stewart Warner sensor from Summit, they sell them in 5* increments.
