[68coupe&06GT]

Hey all, My 68 is running hot and overheating...I detected a leak coming from the heater core...would this cause it to overheat?
Thanks!

[RF Mustang]

only if it leaked so much coolant that it ran low on coolant. otherwise, NO. Assuming you have not been fooling with the timing, Check the basic's.
-Were you doing something out of the norm (city traffic on a hot day)
-Is water pump pumping coolant ? (pull heater hose off at manifold and attach another hose out the front, start car. it will shoot better than a garden hose)
-Is the radiator old and need flushed ?
-Is your thermostat bad and not opening up ! (with car running, how much coolant is pumping into top of radiator. open cap (after its cooled down) and see)

[68coupe&06GT]

I am assuming that the water pump is bad, it looks like an original, or very old...I just repolaced the thermostat...

Explain more to me how to do the hose test...are you talking about the hose that goes into the thermostat housing near the front of the intake manifold?

[RF Mustang]

IOnce the car has safely cooled down (preferrable after setting a couple hours), do the following. One of you heater hoses connect to the hose fitting at the top of your intake manifold near the thermostat housing. Pull the hose off and plug the heater hose you just removed either with a taper punch or fold it in half and clamp it with some vice grips (so no water escapes). Put a 6 foot piece of heater hose on the fitting you just removed your heater hose from on the intake manifold. Place the other end of the hose out the front of the car an away from everything or better yet, in a 5 gallon bucket. Make sure you filled the radiator with water. Start the car. You will see a stream come out at a rate higher than a garden hose. it will pump a good 6 to 10 foot stream. The water coming out is coming from the engine block that is being pumped in by your pump.

it's easy to do and a sure fire way to know your pump is pumping proerply. Dont let the engine any longer than it takes you to see the result due to pumping out the water

[68coupe&06GT]

Ok cool...Also, come to think of it, I did just have a mechanic do some tune up work on it, where the timing was adjusted. He also did oil, plugs, wires, points, condensers, and carb adjustment. I saw you said something in the first response about the timing...how would that effect it? And how would I fix that?

[RF Mustang]

If you had a mechanic set the timing, then its most likely okay. Sometimes people play around with their timing and set it to high. When you do this, it makes the engine run hotter. i have seen exhaust manifolds almost glowing hot because of this. Timing on a stock 289/302 should be somewhere around 6 to 14 degrees BTDC (pending any performance cam your using) at idle and no vacuum.

If you replace your water pump. Flush your engine and radiator. well before you add coolant. I would set up for the water pump test proceedure as i indicated earlier except i would run a garden hose in the radiator filling it with water as it is being pumped out. you would be suprosed at the crap that will come out of their. When you are all said and down. Fill your car with water only and drive it to see if it overheats. This way if it does, you wont loose expensive coolant. If everything is okay, drain the old water and start the engine to circulate some out of the block. Then add the proper coolant mixture. there will still be water in the block so I would use straight antifreeze coolant so you get a 50/50 mixture. Save some room to add a quart of water additive for the radiator. Spend a few dollars and add a water additive called water Wetter (its a red fluid). It helps you cooling system but also helps drop water temp by 20 degree's. I noticed a difference in both of my mustangs.

[RF Mustang]

boy..... you can tell my fingers are "fat' and i'm accustom to using spell check with microsoft word.

[68coupe&06GT]

Awesome, Thanks for the help!!!