temp to high

shifty66 · Jul 31, 2005

heys guys, I've got a 66 stang with a 302 in it. the orginal car was a 6 cylinder. my problem is the tempature get to high on the highway.I' got a 2 row radiator with I believe a 6 blade flex fan. I've put in a new 160 thermostat. flushed the radiator, added a shroud, and still gets hot. I can drive all day around town and temp will stay at about 190 but when I getI get it on the highway it slowly creeps up to about 230. Get back into town and back to 190. What's the problem? need new radiator or have this one rodded.

68torino · Jul 31, 2005

I've run vehicles for 35 yrs and have seen this several times. Put in a 190* stat. This will hold the coolant a little longer to allow what is in the rad to cool. As long as everything else is up to snuff.

ForceFed70 · Aug 1, 2005

Ugh... It's not the thermostat! By that logic.. the coolent spends less time in the engine and also has less time to "heat up". The engine still produces the same amount of heat and the radiator still removes the same amount of heat...irregardless of the thermostat and the speed at which the coolent moves through the system.

Overheating at speed generally indicates a circulation problem.

rbohm · Aug 1, 2005

70 is right, it is not the stat. likely the rad has some tubes blocked. put your hand on the rad when the engine is warmed up and you will likely feel some cold or cool spots. this indicates that you have less area for the coolant to reject heat.

brianj5600 · Aug 1, 2005

Gotta spring in the lower hose? Heat exchangers extract more heat the higher the temp differential. More heat will be extracted from 190* water in 100* air than 160* water and 100* air. Don't make me get out a physics book out on you! I don't think it is the t stat because it is wide open on the highway.

grego37 · Aug 1, 2005

Waterpump?

Do you have stock pulleys?

4MuscleMachines · Aug 1, 2005

do you have the heater core connected? If not, make sure you loop the outlet/inlet on the water pump and not just cap them. Capping can prevent good circulation at highway speeds.

ForceFed70 · Aug 1, 2005

brianj5600 said:
Heat exchangers extract more heat the higher the temp differential. More heat will be extracted from 190* water in 100* air than 160* water and 100* air. Don't make me get out a physics book out on you! I don't think it is the t stat because it is wide open on the highway.

Who are you refering to? Because if it's me I agree 100%. No need to bust out the books.

brianj5600 · Aug 1, 2005

4MuscleMachines said:
do you have the heater core connected? If not, make sure you loop the outlet/inlet on the water pump and not just cap them. Capping can prevent good circulation at highway speeds.

I thought that there is no water circulating through those hoses if you select cool on the temp control. Why would it be different from plugging them?

ForceFed70 · Aug 1, 2005

brianj5600 said:
I thought that there is no water circulating through those hoses if you select cool on the temp control. Why would it be different from plugging them?

I believe when you select "cool" you are just causing the air to not blow through the heater core. That's why the change is so quick from hot to cold.

D.Hearne · Aug 1, 2005

70_Nitrous_Eater said:
I believe when you select "cool" you are just causing the air to not blow through the heater core. That's why the change is so quick from hot to cold.

That would depend on how the system is set up. Some heaters have shut off valves that are either vacuum or mechanically operated and shut the coolant flow off when you turn the heater off, some don't. If he's still running the 6 cylinder radiator with the 302, then there's the problem. Need a larger radiator with more surface area for a larger engine.

68torino · Aug 1, 2005

When you choose 'cool' on your heater control you close off the coolant valve to the heater core.
Since you have flushed your system I would put in a 190*-195* stat. It will work, been there done that.
I had a '66 F100 300 six with a radiator that Ford also used on for the 390. My problem was it ran to cold in the winter even after putting in a 190*-195* stat.

If you want to you can take a heater core or AC coil mounted in front of your radiator. Hook up your heater hoses to it and gain some cooling. Did that with a '79 'stang. Which really needed a flush but we went field expediant due to costs and time. No money and no time.

ForceFed70 · Aug 1, 2005

D.Hearne said:
That would depend on how the system is set up. Some heaters have shut off valves that are either vacuum or mechanically operated and shut the coolant flow off when you turn the heater off, some don't. If he's still running the 6 cylinder radiator with the 302, then there's the problem. Need a larger radiator with more surface area for a larger engine.

Some heaters do shut off the coolant flow. But does this happen in a classic mustang? I honestly don't know. What I do know is that no such valve exists in my 70. The temp selector controlls a door and controls how much air is diverted through the heater core.

This may be different for factory AC cars tho..

D.Hearne · Aug 1, 2005

My 67 didn't have a valve to stop the coolant flow when I bought it ( it was 13 years old by then) And still didn't when I sold it. I had installed manual shut offs by then. Some do, some don't.

brianj5600 · Aug 1, 2005

Flow or no flow the water running through the hvac won't cool much w/o air flowing through the heater core.

dennis112 · Aug 2, 2005

You should replaced the radiator with either a 3 row model or go aluminum. Your original may be somewhat clogged. Rodding it out may or may not work or could be only a temporary fix--there are no guarantees.

On 65'/66' Mustang the heater knobs control ONLY the air flow. The engine water hoses go straight into the heater core and right back to the engine block. There are NO water ON/OFF controls.

351carlo · Aug 2, 2005

Just an FYI, Factory A/C 70 cars have the flow control valve. Vacuum operated Bypass valve which shuts off water flow to heater core if A/C is operational.

Sounds to me like a flow problem. Most likely at high RPM's you're not circulating what you need to. Anyone else think maybe his timing is off enough to throw some extra heat when it's advanced?

Max Power · Aug 2, 2005

Agree with 351carlo, A/C cars tend to have the shut off valve.

I too swapped a 302 into a 69 coupe that had a six. The radiator couldn't keep up. Put in a decent V-8 radiator and your problem should be solved.

Carlo, on the timing thing, cars tend to run hotter without ENOUGH advance....

krash kendall · Aug 2, 2005

I think you wll find that the radiators for a V8 and I6 in the '65-'66 model years are identical except for the inlet and outlet size. However, a three row is available to replace your two row, and same size or not, a new three row will out-perform a questionable two row anyday. And Carlo and Max are right - no flow shut off in early cars. The A/C didn't run through the heater ducting so the heater core was already isolated from the A/C system.

shifty66 · Aug 9, 2005

thanks guys for the info I think I'll just replace the radiator

temp to high

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