68 Cooling Problems

[mbryson12]

I have a 1968 with a 6 cylinder and 3 on the tree in it. For some reason it keeps overheating on me. I have replaced the thermostat on it, but it still seems to overheat going up hills. It came from sea level where it had no problems. I now live at 8500 feet in Colorado. Could it need a new radiator or a water pump? I can't pin point where the antifreeze is coming from when it does overheat, but it doesn't take much for it to boil over. After replacing the thermostat it seemed to be doing much better, but it blew out on me coming back up to my house. Any ideas on where to start?

[AlleyCat]

A good place to start is to look over all of the cooling system parts. Make sure the belt(s) are in good shape and snug. Also look for antifreeze leaks. Whiteish stains are residue from leaking antifreeze that has dried up. Another part of basic cooling system maintenance is to use compressed air to blow the dirt and bugs out of the radiator fins. Point the air nozzle at the engine side of the rad and blow air forward. Be careful not to put the nozzle directly on the fins as an old rad can be damaged from high pressure air on weak metal. Next borrow/rent/buy a cooling system pressure tester. Put about 10 psi on the system and look for leaks. Hopefully it's something simple causing the problem. Something else to check is to look into the filler neck with the engine running and up to normal operating temp. The coolant in the top of the rad should be moving. If it's not the rad is plugged or the impeller in the water pump is damaged or spun off of the shaft. Plugged rad tubes are a far more common problem than a damaged impeller.

[hotrodfeguy]

Just another idea I put a shroud on my truck from a dentside. Never had any problems since. But i like to run alot of time in the old FE.

[FreakysFords]

With the change in elevation, I have 2 suggestions.

Check the base timing AND that it's advancing correctly.
Check the fan clutch that it's actually fully engaged when engine hot.

Beyond those two, if uncertain of the cooling system's condition, I'd likely flush the system.

Hope this helps
Frank

[willowbilly3]

Also don't forget to check the timing.

[DuckRyder]

In additon to timing, check the mixture as well, for that change in altitude you may even have to re-jet the carb...

[NM5K]

well, yea the timing and mix can make it run hotter, but usually there is plenty
enough cooling overhead to handle those types of changes.
I think this guy needs a radiator the same as the other one I just
posted to.
Usually a normal cooling system has enough reserve capacity to
handle timing changes, etc. And I'm betting his timing is fairly
normal.. Wouldn't run too well if it was too far off.
Sounds like radiator time to me.. A common problem on many
of these old trucks as many have old half shot radiators.