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Confused on my 73 Challenger 340

mj73rallye

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Hey everyone, looking for some help. Im a newer owner of a 73 Challenger with a 340. Everytime I drive it, the engine temp gauge "goes high". By that, it get to the very top of the "operating range" just below the H. Most cars I would assume its overheating. I have replaced the t-stat as prior, it would go into hot. Now it stays around that top line. I grabbed an infrared temp gun and just idled the vehicle and it did the same. In checking temps, the t-stat housing with peak about 210 ish? and same for the intake. Heads are typically a little cooler. I tried to replace the temp sensor just in case...no changes. No obvious issues with Rad either in scanning with the temp gun. and the clutch fan appears to be working. It has its shroud in place as well.

Is this a normal range since it doesnt go over line just stay there? Doesnt seem like it to me...

gauge.jpg
 

Challenger RTA

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Check both your thermostats. boil water in a cup drop in see if they open. remove see if they close completely. If it is open before you test it's bad.
 
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Challenger RTA

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As far a temp that might be a little high. depending on what thermostat,ambient temp, A/C on,stop and go traffic? Does it cool down at highway speed?
 

mj73rallye

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Thanks for all the comments guys. This was all idling, but it doesnt change when driving. Acts the exact same. Basically always around that temp. It is an AC car but nothing hooked up (compressor removed). Another note, it never pukes anything out the overflow hose at top of radiator. When Idleing and getting up to temp and cap off, I can see I am getting movement of the coolant as well.
 

Challenger RTA

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When Idling and getting up to temp. It takes a while for the thermostat to open. should not see any movement until it opens. check thermostats.
 

Chryco Psycho

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You may not have any problem the gauge could just be not working properly being over 50 years old
 

mj73rallye

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You may not have any problem the gauge could just be not working properly being over 50 years old
Thats really what I am hoping for. Like I said, hoteest I saw was like 210 at t-stat housing, nothing hotter. But very consistant.
 

mj73rallye

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Temp sender was replaced......sending unit I was talking about being bad was the fuel sender.
 

tonysrt

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I would definitely look into the radiator if it is the original one. Drain some of the fluid in it and look at cooling tubes to see if they are clogged, if they are may want to have it boiled out or put a new one in. Years ago nobody used distilled water when changing antifreeze. A good flushing out of the block and radiator may also make an improvement in cooling. Don't forget your dealing with a 50 year old car.
 

pschlosser

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You may have a voltage limiter going bad on the back of the gauges if there all acting up.
I'm gonna second what @Challenger RT said. The voltage limiter is a common failure point and, in some case, when it fails completely, it takes out a few gauges with it.

Some of the gauges operate on a 5? volt system and the car is 12-volt. It could be the limiter is only starting to go bad, and has not ruined any gauges.... yet.

I'm unsure the test procedure but I'd be inclined to make sure it's working before turning on the ignition again. There is an updated solid state limiter that is the one to get, if I recall correctly.
 

mj73rallye

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I have a temp gauge laying around...I could plug that n to check the temp more accurately than the infared gun...what should operating temp be? I feel like that 185-200 should be normalish???
 

Xcudame

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Check your dash voltage regulator. Or better yet, buy a modern electronic one. About $50. The old one is like a set up points and pulses 5 volts from the 12 volt system. Plus the 50 year old temperature gauge in the dash could just read high. 210°F isn't bad. Remember that with the 15 psi system pressure, water boils at about 250°F. Even higher if you're running 50/50 antifreeze.
 

volunteer

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If car is indeed hot, suspect rad core - if gauge indicates hot, but temp is normal - likely faulty or incorrect sending unit (new or old).
 
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