1966 mustang runs hot at idle

Hi, I see you've done quite a bit. My first thought is with the 160 stat. and the high volume pump and the under drive pulley, you are moving the water too fast and it is not staying in the radiator long enough to cool. I would start by putting in a 180 or 190 stat to slow down the water flow. The reason I believe you're running cool while moving is the extra airflow through the rad. Good Luck Let us know what you find out.

what if i used a water outlet restrictor,if so what size would you suggest?

I would only use a water restrictor in extreme conditions, racing, demo derby, etc. where the risk of stat failure and engine can go unnoticed until it's too late. The stat regulates water flow opening and closing by temperature. When functioning properly it keeps the temp. constant. with a restrictor your flow can change with the speed of the engine but not with temp. I would really say to go with a 180 or 190 stat. If the 180 helps but not enough, switch to 190. Let us know. Good Luck

i put a 195 thermostat in and a 100amp.alt.,the fan was drawing 10 amps.and old alt.was putting out less then 25amps.at idle.system works much better,water temp.was about 200 after about 10 minutes at idle,very hot and humid here.thanks for the help, butch

If you don't have a fan shroud built in with the fan I suggest you get one. when a car overheats at idle it is not getting enough air through the radiator to keep it cool. Going down the highway the fan isn't even necessary due to the amount of air the car pushes through the radiator. A good fan shroud should fix the problem if the fan you are using has enough air flow. Some of the electric fans are simply not up to the demands of our cars at an idle.

I have the same issue, hot at idle or slow cruising, but normal at highway speeds.

I measured the hose temperatures at the inlet and outlet at idle, and it's about 225*F at the inlet, and about 215*F at the outlet, so it seems the water is circulating too fast and not being cooled properly in the radiator. Unfortunately I don't know what temp thermostat I have.

My cooling setup is similar to butch88's, but I'm running a 347 stroker. Do these normally run hotter than stock? My pulley setup is such that I can't fit the fan behind the radiator, so it blowing from the front.

desdain said:

I have the same issue, hot at idle or slow cruising, but normal at highway speeds.

I measured the hose temperatures at the inlet and outlet at idle, and it's about 225*F at the inlet, and about 215*F at the outlet, so it seems the water is circulating too fast and not being cooled properly in the radiator. Unfortunately I don't know what temp thermostat I have.

My cooling setup is similar to butch88's, but I'm running a 347 stroker. Do these normally run hotter than stock? My pulley setup is such that I can't fit the fan behind the radiator, so it blowing from the front.

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hp makes heat...sounds like you don't have enough radiator. I've got a mild ford racing crate motor with a very large 2 row aluminum radiator and a 195 stat...it stays under 200 degrees in any heat whether at idle or at speed.

v8only said:

hp makes heat...sounds like you don't have enough radiator. I've got a mild ford racing crate motor with a very large 2 row aluminum radiator and a 195 stat...it stays under 200 degrees in any heat whether at idle or at speed.

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I have a brand new aluminum radiator, so hopefully that's not the issue. Due to space restrictions, I can't put anything too big in there, which is why I went with a new aluminum as opposed to the original type.

Okay, I added some pics of my radiator. It's a 2 row with about 1 inch channels, but I'm not sure about the brand as I can't find the papers right now. Surely this can handle a 347 stroker that is mainly being "cruised"?

I've also added a couple of pics to indicate the lack of space between the radiator and the pulley setup, as well as the thickness of the radiator.

I don't mean to hijack this thread, it's just that my situation is so similar to butchd88's.

this is probably a dumb question but do you have your fan set up as a pusher,if so did you reverse the fanblades?

butchd88 said:

this is probably a dumb question but do you have your fan set up as a pusher,if so did you reverse the fanblades?

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Not a dumb question at all :winks , but yes, it's set up as a pusher and the blades are oriented correctly. There is a solid stream of air blowing through the radiator. In fact, in just about 10 seconds after turning off the motor, the majority of the radiator fins are cool to the touch (not the areas not covered by the fan though).

I think what I'll do next is measure the temperature at the thermostat housing with an IR thermometer when the thermostat opens. Hopefully this will give me an indication of what temperature my thermostat is without taking the cooling system apart. In my neck o' the woods I can't just run to the parts store to pick up a different thermostat, as they are special order items here :sosad: