New to the HAMB. Have a 1963 T-Bird with an engine that only overheats on highway. Done/verified the following:
1-No apparent coolant leaks.
2-No heating issue at idle.
3-Heat sender seems to be operating fine.
4-Thermostat opens and pump is circulating the coolant.
5-Checked for head gasket leaks using block tester no combustion gases detected.
6-
Radiator in good shape.
7-
Radiator fan has excellent air movement.
8- No sign that water is getting in the oil.
9-
Radiator hoses and belts recently installed.
10- All cylinders have 120 lbs pressure
Any ideas as to what to do or where to look are appreciated.
Thanks
Here are some more things to check:
1. Remove a core plug and poke into the water jackets. Heavy
rust/mineral deposits block heat transfer and may require removal of all core plugs with mechanical cleanout or even entire block soaking. Blocked jacket flow will cause local hot spots and risk a blown engine.
2. hydraulic clutch on fan is usually worn out. But you usually don't need or benefit from a fan at highway speed. Do you still have a shroud?
3. 120 pounds is quite marginal. It suggests that vacuum might be inadequate, that vacuum advance does not work, and that engine has too much ignition advance at highway speed, causing overheating and even possible detonation. The engine may be worn out and too difficult to ever get tuned. Nearly all of these old FOMOCOs using points have a worn out distributor that causes erratic ignition timing and a rough idle. My trusty Ford dealer tried to sell me an also worn out distributor that he claimed was "rebuilt." Push the cam back and forth and note that the points open and close even when the shaft is not turning. It is well worth it to install an
electronic ignition kit that fits inside the old distributor. But this might not fix overheating. With 120 pounds compression, you might be able to limp along for another 5000 miles which might be enough for a collector car. But it might be too much hassle.
4. Older muscle cars use
carburetor jetting set up for old high octane gasoline. On today's gasoline they will often run too lean, contributing to overheating. The answer may be to install a larger main jet.
5. It is difficult to know the flow rate of an old
radiator, but it is usually blocked. It is easier and cheaper to simply buy a new
radiator.
Rock Auto has great prices, maybe under $50. Local
radiator shops are competitive and often deliver. Depending on price, convert to a higher capacity
radiator, such as five or six core.
6. American made thermostats will break if you cough too hard when the hood is open. When I put them into a test pot of boiling water, most are defective. Your new thermostat may have broken the first time your old engine overheated. If you can find a Toyota or Mercedes
OEM thermostat the right size, it is much more reliable. Try your local dealer but be sure he sells
OEM and not aftermarket junk. I believe the little hole is essential and should never be blocked.
7. Check for loose belt(s). Maybe purchase a belt tension gauge and tighten to specs.
8. Check that there is clean air flow into
radiator, through it, and also exiting the engine compartment. There should be no changes to the thoughtful factory design. At highway speeds the fan does nothing and it is all about maximum air flow pushed through by vehicle movement.
9. Old heat sensors are unlikely to be reliable/ accurate. Install a gauge with a tee fitting to use both.
Harbor Freight is good enough.
10. If all else fails, consider converting to racing coolant that boils at about 300. It also has better heat transfer, is less likely to cavitate, and never needs changing. First update all cooling
parts,
radiator, heater hoses, water pump, thermostat, etc. Special flush and then run the racing coolant straight. Enthusiasts will often update from an old two or three core
radiator to a five core
radiator which usually helps.
