Radiator flow questions on '67 390 GTA - Ford Mustang Forum
 
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post #1 of 6 (permalink) Old 11-11-2013 Thread Starter
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Radiator flow questions on '67 390 GTA

I Have '67 390 GTA. I bought car where previous owner had people literally replaced/touched every part on car in totall restoration. Have been having some cooling issues that we are working on--- installed new thermal fan clutch, 7 blade fan and fine tuning the ignition. While running engine in garage at idle with radiator cap off, were very surprised to see rapid fluid flow inside radiator. The water pump appears to be stock. We are concerned that flow is too rapid and fluid isn't in radiator long enough to "be cooled". This normal? Thoughts? Thx Omaha Bill

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post #2 of 6 (permalink) Old 11-11-2013
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Thermostat issue?

Rapid flow into the radiator usually indicates a missing or stuck open thermostat. Normal operation is for the stat to stay closed until it's operating temp point is reached (somewhere around 160 on the older cars). It opens and lets in the cooler water from the radiator. This cause the stat to close and the process starts all over again.
If the water is not cooling down in the radiator, this could cause the symptom you describe as the stat is open due to high water temp. Shut the car off and feel the front of the radiator from left to right, top to bottom. There should be no 'cold spots' within the radiator.
One other issue that would cause high water temps with a properly operating stat would/could be a head gasket problem.

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post #3 of 6 (permalink) Old 11-12-2013
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To check the thermostat, start the engine when cold, let it run with the hood open, use your hand and feel the heater hoses, the inlet to the heater core (bottom hose on the firewall) should be warming up, if you touch the top radiator hose at the radiator it should still feel cold, if it is feeling warm also, and near the same temperature as the heater hose, then the thermostat is open or missing, neither is a good condition. IF you have a good thermostat, When the bottom heater hose is getting hot, the top radiator hose should be getting hot near the thermostat housing but not so much at the radiator, when the thermostat finally opens, then the top radiator hose will be hot all the way across and you should feel warm to hot air blowing from the radiator. Good Luck.
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post #4 of 6 (permalink) Old 11-12-2013
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sounds like it could be a thermostat issue,,hang it in a pot of water and heat the water up,,,you should see the thermostat open at about the temp. stamped on it,,do this with a new thermostat also,,I have gotten bad ones before,,
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post #5 of 6 (permalink) Old 11-12-2013 Thread Starter
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Guys, appreciate your responses. I mis spoke when I commente about rapid flow at idle implying that thermastat was stuck open. The rapid flow is occuring after the thermastat is open. So my question, is rapid flow something normal/what you have seen in your 390's? Also, where on your temp gauges( 1/3, 1/2, 3/4) does needle usally end up when operating on 60 degree days and on 75 degree days? Thx--Omaha Bill
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post #6 of 6 (permalink) Old 11-12-2013
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One of the greatest impactors that has come to be are the "high-flow" replacement water pumps that were introduced (and still here) in the late 70's......although 99% of it is a better impellor design, it did increase the flow rate of coolant in the system.....Now originally, the increased flow was 3% IIRR which still gave a good amount of time for the coolant to absorb the heat and expell it at the radiator but over the years & especially in the mid 80's the engineers upped the design again and well, that's when we all starting to see our engines running warmer (you also have to remember at the time these same style water pumps were still in use on the new vehicles- which were designed for the increased flow). On our Mustang the flow was so great that it would cause the radiator cap seal to "lift" under higher rpm causing fluid to expell, which we addressed with an overrflow/recovery tank (had to home-build that one at the time), which today is a common standard so to speak.
The increased flow/cooling issue is really nothing new though, as with the flatheads- had the same/similar problem caused in part by increased HP/TQ & speed- the solution was to install a giant washer (restrictor) at the upper radiator inlet- this slowed the flow to allow greater absorbsion/cooling.
IMHO, it really all depends on the radiator specs if it was of a design to 'handle" that specific engine, etc...you just are not going to know until you take it out for a drive, but from they way it sounds as you have described, the "assembler" didn't just buy parts off the e-net that said it fit x-car with x-engine and actually did their homework selecting each component specifically (which if you don't do even on new cars will get you into trouble).


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