I have been keeping notes on all the overheating thread on the PY site and making a list of resolution.

I'm sharing this for anyone to use as a check list. Remember these are just notes. Cut and pasted in notepad. I did not write these.


"What is your definition of "overheating"? There are three common definitions, and I'm not fond of either of the first two:

1. The coolant is actually boiling out the rad cap overflow hose. The temperature required to do this varies with system pressure and anti-freeze concentration. If the coolant is actually boiling out the overflow, the engine has probably already suffered some amount of damage.

2. The coolant temperature is at or above some specified temperature. Different people specify different temperatures. Some "hot" light sensors didn't trigger until 260F. Another issue is WHERE the temperature is measured. Sensors next to an exhaust manifold tend to read higher than sensors in the intake manifold coolant crossover. The engine is in imminent danger of damage.

3. The coolant temperature at or near the thermostat is more than 15 degrees above the thermostat rating, at idle or cruise. A thermostat is intended to set a MINIMUM operating temperature, not the maximum temperature. If the coolant temperature measured near the thermostat is more than 15 degrees above the thermostat rating, the theromostat has no control over system temperature. It has "lost control" of the temperature. The closer the system temperature is to the thermostat rating, at idle or cruise, the better. System temperature will increase somewhat for heavy-throttle or high-rpm use, but when the vehicle returns to idle or cruise, the temperature better go right back down to near the thermostat rating.

A 50/50 is for modern AC cars...if your car does not have AC , best cooling of coolant and water is 33 % coolant 67% water...the most efficient cooling mixture...but AC cars use a higher % for lubrication IIRC.


*Clogged/Dirty Radiator not flowing properply
*Collapsed hoses
* Blow-by finding it way into coolant->Causes foaming->drasticly reduces heat transfer (Do a Pressure Test) Blown head gasket for example.
*Divider plate clearanced appropriately
*Test thermostate in boiling water
*Air pockets? Drill 1/4 hole in thermostate to pass air pockets.
*Type of impeller - Cast is always better and not all cast impellers are the same some are deeper then others.
*Fan shrowd in place? air dams in place? baffles in place? Fan clearence around fan shrowd
*Temp infread gun can be a great troubleshooting tool- compare input temp to output temps of the radiator and look for cool spots or hot spots. Can be used to compare accuracy of gauge/Sender.
*faulty gauge - A second gauge check is always a good idea
*clutch Flex or Electric - Its tough to beat a good factory 7 blade with HD clutch.
*If electric - is your fan a puller or pusher? pusher fans are not good ,they also block radiator
*rich or lean carb setting.
*Vacumm leaks cuase lean conditions Carb bolted down? Orange intake alignment pieces?
*timming issue - Try simply backoff on the timing and see what happens
*Over heating at idle or driving - Generally If at idle or very low speed, then it is likely an airflow problem. If at speed, then it is likely a coolant
*Retarded cam - Cam not degreed in correctly on ILC. Read about this more then once.
*WP pully diameter for trouble shooting
*deck height - Piston down in the hole makes for bad quech.
*8 realief pistons notorious for ping and heat realated issues.
*Clutch fan test See the PDF in Personal->Car stuff. Cold should spin 3 times or more when you shut off the motor. Hot should spin less then 3.
*Adjust Clutch fan for max friction PDF in Personal->Car stuff.

2 row aluminum with 1.25 tubes cured vs 4 row aluminum
radiator flush
cams with too much overlap
Radiator cap pressure
radiator hose is collapsing (needs a spring).
casting shifts hot spots