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Discussion Starter · #1 ·
I bought a used Dodge Charger, knowing that it had an overheating issue. I've taken it to two mechanics and have determined that has enough coolant and the car has been pressure tested with no leaks found. What other tests should I run to find the problem and then have a mechanic fix it, or even attempt to fix it myself?

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Depending on what kind of temps you're seeing, I'd suspect the thermostat, water pump, and/or coolant temp sensor.

It could also be clogging caused by incompatible coolant mixing. Your car should have come with HOAT from the factory, but it's very common for owners and even experienced service techs to put in OAT, IAT, or even [shudder] Dex-Cool.
 

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I'd second your thermostat or water pump.
 

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Discussion Starter · #4 ·
Depending on what kind of temps you're seeing, I'd suspect the thermostat, water pump, and/or coolant temp sensor.

It could also be clogging caused by incompatible coolant mixing. Your car should have come with HOAT from the factory, but it's very common for owners and even experienced service techs to put in OAT, IAT, or even [shudder] Dex-Cool.
I'd second your thermostat or water pump.
How could I tell if it's a blown head gasket? If I remember correctly, the temperature goes all the way to the red on the furthest it can go. The mechanic said he used the correct coolant and didn't say he used HOAT though. He did say that he doesn't have the vacuum to flush all the coolant out.
 

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How could I tell if it's a blown head gasket? If I remember correctly, the temperature goes all the way to the red on the furthest it can go.
Sure sounds like a stuck thermostat.

There are a number of ways to check for a bad head gasket. One is a pressure test, which you say it has already passed. You could also try a combustion leak detector kit, or a compression test. Have you checked your oil and coolant for bubbles and signs of contamination?

The mechanic said he used the correct coolant and didn't say he used HOAT though.
Yeah, right. I'm sure if he used OAT, IAT or Dex-Cool, he would have said, "I cannot tell a lie. I used the wrong coolant". Even if he didn't, the car's fifteen years old. Someone else may have used the wrong stuff in the past.

Flushing your cooling system is fairly straightfoward, you just need a lot of patience and plenty of distilled water (about 90¢ per gallon at Wallyworld).
 

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Discussion Starter · #6 ·
Have you checked your oil and coolant for bubbles and signs of contamination?
When I first got it, it didn't have coolant in it, so I filled the coolant tank with PEAK Antifreeze/Coolant Universal 50/50 PREMIXED, but I'm guessing I would need to use something like this?

Also I've only seen the coolant bubble when the car is overheating. I have not checked the oil for bubbles or contamination. I haven't checked the coolant for contamination and when the 2nd mechanic filled the car with coolant he told me the engine also has to have coolant in it. So when I put 1 gallon of the PEAK coolant in the reservoir, he then put more in.

I wasn't able to determine which type of coolant the Peak is. The same mechanic quoted me $195 to replace the thermostat.

Would you recommend flushing the coolant and replacing it with the Zerex or first getting that combustion leak test done? Also is the combustion leak test as accurate as the more expensive compression test?


 

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Discussion Starter · #7 ·
Have you checked your oil and coolant for bubbles and signs of contamination?
I bought the combustion leak detector test only to realize all my coolant is gone, what can this mean? Does that mean the mechanic never did a pressure test?
 

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You have a massive leak somewhere (probably the radiator itself--the plastic end caps crack when they get old) fill it up with plain water and watch to see where it goes while it is idling. (and the Zerex G05 is the correct coolant for pre 2013 models). The old 3.5 has lots of places where it can leak: radiator, water pump, hoses, heater hoses, heater core, the lower intake manifold gasket, or the head gasket. The lower intake manifold gasket is potentially deadly- it lets the lookant leak into the intake port and can hydro lock the engine (AKA kill it). The water pump is not visible (under the timing belt cover) and if it is leaking it will take out the timing belt and potentially bend the valves (look for water coming out the timing belt cover near the bottom (Video shows where it is and how to change it- it is a royal pain in the butt to do).

1st pic shows where the lower intake manifold gasket leak can occur, 2nd pic shows what happens when you use the wrong coolant..

 

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