Hi,
So I decided to buy a Ford after many years of being a GM man. So now I own to classic cars, I have a convertible 1968 Pontiac Firebird 350 with a 4 speed and now a 1966 289 mustang. I bought the car a few months ago and the car was overheating. So I originally changed the following items:
Radiator hoses (ALL OF THEM)
Radiator
Radiator cap
Thermostat (TWICE)
Water pump
All that did not fix the problem. So then I thought maybe there is something wrong with the heads or block, and since there was white smoke and the car was burning a little oil, I decided to get a rebuilt engine and heads. So I bought the engine off craigslist from a guy who claimed it was rebuilt and it looked great when I took off the heads. Everything looked fine, so then I installed the engine and heads. The car still overheats!!! So I changed the following:
Water pump
Thermostat
Still didn't fix the issue. So what is really really weird is that the car will NOT overheat at idle, and it will take a very long time to overheat in the city, but as soon as I take it on the highway, it overheats in about 10 miles. The old engine/heads and the rebuilt engine/heads both exhibit the same behavior of overheating!!???!?! It is really weird and I'm not sure what to do at this point. The car has an automatic tranny, 4 barrel carb, stock cam, so I don't think it would need a tranny cooler since it's stock. I don't have a fan shroud, but that isn't the problem since it's overheating on the highway. The tranny is not slipping, my timing is perfect and I don't have the heater hoses reversed or anything stupid like that!!! When I turn on my heater, it gets hot and helps the car not overheat as fast. Now all my GM buddies are telling me "I TOLD YOU SO!!!!!!!!!!" I love the body style of the car, I love the way it drives and I don't want to give up on it just yet. Do any of you have any suggestions?

 

You can try a couple of things. Check the bottom radiator hose to make sure it has a spring in it to keep the hose from collapsing under pressure. Add a shroud. Even on the highway, that will help pull the air toward the center of the radiator. Add an electric fan. Use a bottle of WaterWetter, Add a recovery bottle. Make sure you have at least a 3 row radiator. You may even consider getting an aluminum one.

 

Thanks for the advice. But I really want to find the root cause of the problem and fix it, not mask the problem. I have a new 3 row radiator, but why would I have to add an electric fan, WaterWetter, a recovery bottle or any other non-stock items if this is a stock car? I would assume the original design should be more than sufficient to keep the car cool. I am thinking something is wrong and needs to be corrected, not patched up by adding a high performance water pump, a 4 row aluminum radiator and all that other stuff. My Pontiac has a hot cam, and a bunch of other stuff that would make it run a bit warmer, but the stock cooling system still works perfectly. So I would assume the Mustang should work with all stock parts. Thanks again.

 

This is a problem inherent with all classic Mustangs. The 289 runs hot, and requires more water running through the system to keep it cool.

 

So what is the most effective thing to do? Get a high flow water pump? Get an electric fan? I already bought a new 3 row radiator, so maybe I'll buy a hose that has the metal springs in them to avoid the hose from collapsing as well. Thanks again for your help.

 

Start with the cheap things first. The hose with the metal spring in it would be my first thing to buy. If that doesn't fix the problem, then move on to the next cheapest thing which would be an overflow tank, then the shroud, then the pump, etc...Also, check your thermostat to make sure it is a 180 degree thermo...

 

Ok, I'll try those things and get back to everyone. Thanks again. Man, when you go through changing out an entire engine, and then have the same exact problem pop-up... WOW... nothing has annoyed me in life as much as that moment when I was stuck on the freeway at 2:40AM in the morning, my hands are all greasy from working on the installing the final pieces into the car, and my radiator is blowing a whole lot of water onto my windshield!!!!!!!!! But for some strange reason, I stil llove that car!

 

Try this before you do anything. Burp the system. Wait until the engine is cold, then take off the rad cap and turn on the engine. Let it get hot and see if you have bubbles rise to the top of the rad. If you do, then keep adding water/anti-freeze mixture until it stops bubbling and just runs like a fast river. You could very well have air in the system.

 

Yeah I even tried that with the old engine setup and now the rebuilt one as well. I also made sure that the flow of the water in the radiator was correct.

 

Damn bro.....I feel your frustration. Try those other things in order of the cheapest first. You may not being overheating though. What gauge are you using to determine the temp?