I have since solved the problem, but I don't know where to post something so I don't waste everyone's time. Thanks for the tips! Let me know where to post and I'll tell you what happened.

I have a client with a 1965 mustang 289 that has an overheating problem. This client is new to me and thus I do not know the whole history of the problem.

Bottom line is this Car runs nicely but once warm it begins to overheat. With the cabin heater on the temperature will drop and become a little cooler. The upper rad hose is HOT while the lower hose remains cool. Rad problem right?

Wrong! The rad flows nicely and the spring in the lower hose is not impeding the flow nor is it blocking the water pump.

The client had the pump and thermostat changed elsewhere and still the same problem. The client himself changed the thermostat because I told him it may have been installed improperly. To no avail!

My question is (finally), Has anyone heard of this problem? Is it possible that the previous mechanic installed the pump in a wrong manner? Can the impellers be turning the wrong way? It sounds like the pump is turning smoothly.

Sorry for the long thread! Anyone's help would be nice. Thanks

 

Its a hard call but if the upper hose is hot and lower hose is cool and it flows well then I would say its all working properly.

However...properly might not be good enough for the climate...how hot is it out? Maybe an after market Aluminum rad would be in order.

Is he running the stock blade fixed fan?
Does it have a fan shroud that seals well around the rad?
Is the last 1/2 or so of the fan sticking past the shroud?

-Gun

 

+1 on the radiator being OK. The idea is to take it in hot at the top, and send it out cool at the bottom.

Its a longshot, but check the timing. I had a similar issue a month ago. After going away from points to a Pertronix system it idled fine, but when driven it couldn't control it's temperature. Several people here suggested a possible timing problem. Thats what it turned out to be. It was a simple fix. Hope yours is too.

If you want the thread, it's titled "Pertronix Problem, or coincidence?"

 

i have a 1966 mustang-same problem with overheating until i changed the radiator to a 4 core and installed a fan shroud and a 6 bladed fan-overheating problem disappeared-tom

 

Some of these heat problems can be tricky. Exactly when does it get hot? Is it just sitting still? If the car is driving down the road, does it still heat up? Does the temp go up and down or just up gradually? Has he replaced the therm housing recently?

 

What is overheating? Is the thing steaming or just rising? If the system is working properly the lower hose would also get hot in an overheating situation.

+1-Check the timing first. If it's within specs...

Disconnect the upper hose, put a garden hose in the radiator To keep it full and start the sucker up. DO THIS ONLY TO A COLD ENGINE. The water should flow out of the upper hose if the pump is working and there is no blockage.
It's a crude way to see if the system is flowing but it works.

If it flows and seems OK, flush the engine with an engine flush and check again. It could improve.

Try running again, and if it overheats look for a bigger radiator.

 

I installed a brand new three row core rad with a Spal electric fan and still had overheating problems. Turned out to be a blown head gasket. Just something else to check.

 

It's a 44 year old car. What condition is the rad in? You will get flow from a rad with rust blocking some of the fins, but it will slow it enough to cause overheating, especially if it is a factory 2 row. Flush your rad and engine jacket, as Oxnard described.

Carlos

 

I had some overheating issues with my old Cleveland. When I put in my new 383W, I replaced the radiator and entire cooling system except the fan and shroud. I still have overheating issues. When the air temp hit about 95, the car cannot keep cool in traffic. I am convenced it is an air flow issue. On the highway is is cool and a cucumber. I plan to move the condenser from the stock location to a location much closer to the radiator. If that does not fix it, I will install an electric fan to pull more air than the old flex fan. My point is, if everthing looks good, check your air flow.