Author Topic: 1966 Mustang overheating  (Read 12176 times)


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1966 Mustang overheating
« on: April 22, 2012, 03:23:01 PM »
I have a 1966 Mustang with a 302 '68 V8 engine and it overheats.  The car has a high volume Edelbrock Aluminum pump, with a double rolling timing chain,  4 row aluminum radiator from summit, electric fan 16 pull.  The car was sitting for a few years before I bought it.  It has some aftermarket parts for example Unilite Mallory distributor, a Holley 4barrel carburator.  I took the water pump off and it seems to be good but I'm not sure, my friend the mechanic says it's good because it's pumping water.  So then I put it back on and I took the radiator out and flushed it with water and I put it back and the overheating continued.  you drive it like 20 mins and it starts to overheat.  Then I took the heads and took them to a machine shop to be inspected and they were fine so I put them back on with new gaskets everywhere and they were correctly installed.  Seems like the engine is really clean in the inside, like somebody worked in it before, which I like it. It has Shelby springs in the valves.  Took the radiator out again because the top hose was getting stiff like before then I took it to a radiator shop and they flushed it, put it back on and refilled the radiator with anti-freeze and it went down better.  I saw the difference in the temperature, I took it for a drive a few times, short trips and when I got back home the temperature was at like 3/4 between the cold and hot.  When it cooled off I took the top off  the radiator and there were residuals (like tiny rocks/sand) like before I flushed it, then I disconnected the hosed and flushed it again with the water hose, put it back on and it was working at some point satisfactory and after a few short trips it started to overheat again.  Lastly I took it to Jiffy Lube and they flushed it, I thought it was going to work but it made it worse, like in the beginning.

Any advise on how I can fix this?  Do I need a new radiator because it didn't move for so long, or a mechanic fan versus electric fan?  Or because the top hose is getting so stiff, do I need a new water pump even though my mechanic says it's good?

Thank You!!


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Re: 1966 Mustang overheating
« Reply #1 on: April 22, 2012, 03:45:49 PM »
I would start at the easiest route and try a different thermostat , also what is the idle speed of engine . Had a 93 T-bird that would run hot constantly did all the usual checks ,but over looked one minor detail that the idle speed was a tad bit high and  the water was circulating to fast to cool down , i would also check to see that the electric fan is actually coming on at the right temp


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Re: 1966 Mustang overheating
« Reply #2 on: April 22, 2012, 07:49:10 PM »
and when you say overheating are you relying on the gauges alone (Which could have a bad sending unit or ground) or is it puking coolant?

50-50 mix of water antifreeze cools better than straight antifreeze


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Re: 1966 Mustang overheating
« Reply #3 on: May 03, 2012, 08:00:05 AM »
You say that your top radiator hose was getting stiff.  Do you, by chance, have a large spring in the lower hose?  If you don't it may be collapsing, which will restrict water flow through your engine and radiator


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Re: 1966 Mustang overheating
« Reply #4 on: May 04, 2012, 06:04:39 PM »
If you don't already have one, look into a fan shroud.


Bill Reeves

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Re: 1966 Mustang overheating
« Reply #5 on: October 21, 2012, 11:21:06 AM »
My Mustang ran hot because I set the timing before the car was properly warmed up, so when it did warm up, the timing was too high.


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Re: 1966 Mustang overheating
« Reply #6 on: September 17, 2013, 06:45:15 PM »
If you don't have a fan shroud get on it will lower the temp dramatically. Have you replaced your radiator cap or tested it? If not take it down to the auto-part store have them text it with their pump tool if its not to spec replace if its stock replace. Mine was off 2 lbs on a mustang in had changed made big difference. If you can get some block checker from the auto part store a Prestone flush kit a hose to fit in the elbow and some radiator coolant full strength. This will help you to end the problem. When you get home flush the system like it says if its gunky bad get a hose to hose swivle adaptor from homedepot an a 1/2"male mip x 3/8" bushing a y hose hose fitting a half fip to hose fitting and a male air chuck fitting you most likely have a compressor this will help when flushing you will have a y hooked to the fitting the kit has with a garden hose hook to one part of the y and a homemade air to hose fitting. This will make it so your system gets power flushed. You take your Prestone fitting with to make sure you get the right stuff from homedepot. After all this flush system fill let idol in driveway. Then see what happens then if still no go check car with block check. If its bad hopefully it's just a bad head gasket. Oh forgot to state you change the thermostat with a 180. Or even higher if you want hotter in winter 195. Also check below for where its leaking from ex freez plugs can happen. Or could be upper or lower radiator hoses. Make sure not over tighten otherwise can make hose out of round on the tightened end. You can touch around these to check.



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