65 200 6 mustang running kinda hot

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1,227
Location
Columbus Nebraska
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As the title says my 65 mustang with the 200 ci 6 is running a little hot. Not so hot as to be hard on the engine, but hotter than it was, and should. I just checked the water temp in the radiator after a loing run, and it is 194 degrees. Not hot you say. But I have a 160 thermostat in it, and the radiator was just back from the radiator shop and rodded out. SO, the radiator is good, the thermostat is new, the temp gauge is ok, and the water pump seems to be circulating the water fine. My thought is to use vinegar or a commercial cooling system flush. Anything else I can do that doesn't involve major engine teardown. PS, I have had this car for 12 years, and it starts, runs, drives fine, good power and gas mileage. Great car, and used to run perfectly cool, and I always kept fresh antifreeze in it. It also has new hoses on the radiator.
 
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1,227
Location
Columbus Nebraska
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Also, I forgot to mention that I also checked the timing and the vacuum advance, and all OK. This engine was rebuilt about 12 years ago, and has been immaculately cared for since, and it uses no oil, gets great gas mileage, and is driven around 1000 to 1500 miles a year, mostly long drives. This years, due to lack if car shows due to the coved crap, I have hardly had a chance to drive it. I want it to be right, as I do normally drive it 80 to 90 miles to some shows. And it is a NICE car, regularly bring home trophies.
 
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249
Location
Pacific Northwest
It might sound odd, but check your distributor. If the mechanical advance is sticking or the vacuum advance is non operative, the retarded timing can make you run hot. Edit: I see you posted about that just before me.
 
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1,227
Location
Columbus Nebraska
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Both. Does climb some when coming to an idle after running fast, but that is normal. Starting from cold, it warms to about 160+, therm opens, drops some, then over the next maybe 10 miles or so, at slow, or high speed,(60+). it will sloooowly climb to around 190/195. Generally holds there unless going to stop and go traffic.
 
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1,227
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Columbus Nebraska
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I have tried it without a thermostat, and runs the same temp, just takes a few minutes longer to get there. And yes I have checked the radiator temp with a digital meat thermometer, and it reads just like the dash gauge.
 
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2,642
Location
Lakeside, CA
Sounds like a faulty thermostat. Failing open. But then you say you see a drop when it opens. Maybe it's not closing.
 
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1,385
Location
RI
A failed open thermostat would result in the engine running too cool. He even stated it runs similar without a thermostat altogether. It sounds like you may need a larger radiator, and/or a more efficient pump. IMO. Does the engine consume any coolant?
 
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23,717
Location
MA, Mittelfranken.de
I wouldn't be surprised if this were a Stant thermostat. I would try a Reische 170 (NB-54). You may need another fan with more CFM a flex lite or electric add on may bring some relief. When they did the radiator did they pinch off any tubes? Use citric acid to flush the system without the thermostat installed. This way allows for easier filling and flushing and if the T stat is coming out anyway its easier still. https://reischeperformance.com/tstatinfo.html
 
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1,227
Location
Columbus Nebraska
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The cooling system, and everything else, is all as the factory made it. And it used to run perfectly cool under all conditions. Sure, I suppose a bigger radiator, or fan could probablyly make it better, but then it wouldn't be stock anymore. Can't see why it can't be made to work just like it used to. Of course I guess if all else fails, I will try to find a stock appearing HD type radiator. Or just quit driving it in hot weather. Runs nice and cool in 70 degree or cooler weather. Or sell it. Anybody want to buy a BEAUTIFUL 65 Stang 6 cyl automatic. CHEAP
 
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4,093
Location
Los Gatos, CA
I think you need more airflow across the radiator. As Rand suggested, I would use a good thermo clutch, AC type fan and shroud. I like high flow water pumps to aid in cooling. Bigger radiators are great! Good luck! I love your 'Stang!
 
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35,762
Location
ME
You say the rad is hot, which says it's not rejecting heat. I'd look at the fan first. You should feel a heat wave coming from under the hood at hot idle. I don't think this car has a clutch, maybe not even a shroud, but I'd see if what you have is working well. Check to see if your idle speed is stock, it could be low. If it has a flap under the rad to push air up and through, see that you didn't lose it on a curb. Your thermostat and water pump are working well enough, as the heat is making it to the rad. By this point the t-stat temp is irrelevant as it's slammed wide open.
 
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4,084
Location
Texas
I have read , at highway speeds , the fan does not do much . The opposite is true at idle and / or slow driving . Just a guess , is the radiator hose to the suction side of the coolant pump , perhaps collapse ? Restricting coolant flow ? As has been suggested , try citric acid with distilled / demineralized water . Then flush well , followed by coolant .
 
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4,187
Location
Parts Unknown
Originally Posted by WyrTwister
I have read , at highway speeds , the fan does not do much . The opposite is true at idle and / or slow driving . Just a guess , is the radiator hose to the suction side of the coolant pump , perhaps collapse ? Restricting coolant flow ? As has been suggested , try citric acid with distilled / demineralized water . Then flush well , followed by coolant .
It's true. Running hot at highway speeds usually is a water flow issue not an airflow issue. A lower hose on that 200 inline could collapse at high speeds if the hose doesn't have a spring in it or it already disintegrated. Also being a big lump of iron, could be a lot of scale build up too.
 
Messages
249
Location
Pacific Northwest
If it never goes over 210-220f in hot stop and go traffic, then I would not be too worried. 195f is the sweet spot in terms of minimizing engine wear. The cooling systems on these cars was pretty marginal from the factory. My 65 Falcon will run 20 degrees higher in hot summer weather at times but never overheats. The rule of thumb is that low speed overheating indicates airflow problems and highway speed overheating indicates coolant flow problems. From your description, it sounds like a circulation issue. Does cranking the heater up to high make any difference? Other general things to check from higher to lower likelihood: Make sure the outside of the radiator is clean. Spray it down with soapy water and hose off all the bugs and crud. I've seen this knock down temps a good amount before. Flush the system as well as possible. I buy oxalic acid power online and flush with that, followed with a washing soda flush. If you use Prestone flush products, they are so weak you need to leave it in for several days of driving around to do any good at all. I've also heard good reports for Evapo-Rust Thermocure radiator flush. Since you already had the radiator rodded out, this will only help with possibly cleaning crud from the cooling passages in the block/heads. Don't run more than 50/50 mix of antifreeze. 30/70 will cool better. Check the fan clutch if you have one. Try to stop the fan with a rolled up news paper when the engine is hot (be careful!). You want around ~36 degrees of total timing by at least 3000 RPMs with the vacuum advance disconnected. Make sure you're not running lean. Check the spark plugs and compare with online reference images for condition. Have a well fitting fan shroud. The water pump impeller might be corroded to the point of providing poor circulation but this is kind of rare in my experience if the system is not a rusty mess to begin with. A very slightly blown head gasket can cause overheating without much in the way of other noticeable symptoms for a while. Test for combustion gasses from the radiator with a kit, or have a shop perform a test. The engine block may have excessive corrosion and blockage. If you suspect this is the case, you can try to pull the freeze plugs and power flushing with a pressure washer. A huge messy job but might help as a last resort.
 
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17
Location
Southwest
Test the radiator cap and it should be 13 lbs and holding correct pressure. You have the wrong thermostat. It should be 195 degrees.
 
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