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I have 68 convert 302 4v. A 20 inch 4 row radiator freshly rodded. New 180 thermostat that was checked in a pot of water prior to installation. New hoses. 7 blade fan (no shroud). New tsu. New gauge harness. New 13lb cap. Timing is set at 6 btc. Edelbrock carb. Added bottle of water wetter. I live in Arizona. My overheating problems are without the a/c on. Now that you know what I have I'll esplain.
The gauge used to read just under the 1/2 way. Now it is always 3/4 or above. I took two candy thermos and found the radiator temp to be 200 with the gauge at 3/4. Is this bad, good? After running, I'll shut car down and then start it back up. Gauge pins the Hot. After running for two or three minutes the gauge will move down to just above 3/4. Am I running hot? I have checked everything 2 times and am at the end of my rope. Help. Thanks.
 

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No, your car is running at normal temperature. Note: the reason the car's radiator has a pressure cap is to contain water above its normal boiling point, i.e. 212 degrees. The typical cap is 13-15lbs and this should contain the coolant up to about 240 degrees before the system will bypass. One of the things you can do is to install a coolant recovery system that tells you more about what your cooling system is doing. NAPA sells a small tank, I mounted mine using brackets from a fan shroud mounting kit and placed it next to the radiator. I also purchased a line kit from Autozone, connected the radiator and the recovery tank together. Note: the NAPA tank requires drilling out the bottom line nipple into the tank to work properly. Also you'll need a clamp at the bottom of the recovery tank and at the radiator to prevent coolant loss. Use a '88 Ford LTD radiator cap. Before installing cap, fill radiator to the brim with coolant (Prestone, etc.). Pour a small amount into the coolant recovery tank as well. About 1/2" at the bottom. Run car normally and occasionally check the tank. If the coolant recovery level stays as it is, or if it rises a couple inches you are all right. Check it in the morning when the engine is cool and the level should return to the 1/2" mark. If it does everything in your system is copesetic. If it spills over and the next day, no coolant is visible in the coolant recovery tank, its likely not cooling properly. I'll bet its working just fine!
 

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I too live in Arizona and know the extreme heat our cars have to contend with. It seems that your car is running too hot to use the A/C and with a 4 row you definately need a shroud. It takes a lot to pull the air through a 4 row and a A/C condenser. If that doesn't work go with the 24 inch clamp in radiator and coolant recovery system that the other Mustanger recommended. Water is the best coolant so don't go more than 50/50 with the anti freeze Gary
 

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Temp Sending Units are notorious for not being calibrated. When you changed, you simply changed the position of the "normal" temperature reading. TSU's obtained at parts stores are prone to this. Original Ford TSU's are the best.
 
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I have the coolant recovery system you can buy at pep boys or autozone. When engine is cold the coolant is where it is supposed to be on the cold line. When engine is hot the coolant is at the hot line. I borrowed a friends infrared heat thermometer and the upper hose read about 183 and the lower rad hose read at 177 degrees. Seems normal to me. The gauge is at the end just before hitting the H. Do you all think its the gauge? The tsu is not new, sorry I lied, I removed it and cleaned it to look like new. I have had the instrument cluster off a couple of times. Could the problem lay there? Let me know. Thanks
 

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Temperatures seem fine. Cleaning the gauge itself shouldn't be the problem, as it will either work or be fried. Cleaning the TSU might create a problem, as you can remove some of the resistive material if you sand blasted it, for example. I'd still replace the TSU and see if that makes your gauge read lower.

BTW, does your gas gauge read high? If it does, you can reduce both the gas gauge and the temperature gauge (and oil) simultaneously by adjusting the constant voltage regulator on the back of the instrument cluster.
 
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I gave up and purchased a aftermarket temp gauge. It reads at 190-200 without a/c on at idle. At idle with a/c it moves up to 210 - 215 (ouch). At cruise it seems to run 195 - 200 with or without a/c. Thanks for your help. Do you think I need to further pursue this or just chalk it up to 110 degrees in Arizona and the car isn't made to idle with a/c?
 

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I think you're fine, with the exception that A/C cars normally have a fan shroud to help flow the air through the radiator. I'd add one of those, if you don't already. Otherwise, 210* is OK, but a touch high. Boiling point with a good cap is probably 230-235*.
 
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