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Puzzling overheating problem 2005 Dodge Neon

neonowner23 neonowner23
New User | Posts: 7 | Joined: 02/10
Posted: 07/21/10
03:31 PM

My 2005 Dodge Neon SXT started intermittently overheating recently.  I started out on a trip and about 30 minutes later it happened.  Generally the car stays "at temp", but out of the blue it'll start overheating.  I'm getting hot air at the heater but I changed the thermostat 90k miles, I figured it's about time.  That didn't solve the problem.  I flushed and refilled the coolant.  I burped the system and there are no blockages in the engine jacket.  Both fans work and come on when they're supposed to.  Now you're thinking, "Blown head gasket, right?" There is no oil in the coolant, no coolant in the oil and no coolant or oil leaks anywhere.  I'm sure the water pump is working because the temp stays where it's supposed to most of the time.  The car doesn't always overheat when going uphill, but it has twice.  The relays seem to be working fine and I swapped them around to see if I get a different problem..but no, I didn't.  I put in a new temp sensor and replaced the radiator cap because I'm stumped.  All hoses look good.  I checked for a crack in the top of the radiator as this happened in an older Neon I had, where it wouldn't actually leak but I was loosing pressure.

I get OBD2 scan codes for; temp sensor over voltage, camshaft sensor, both fan relays and multiple piston misfires.  I recently reset the check engine light and it has stayed off.  The above codes seem to be intermittent as none have come on again.  I checked all my ground wires because of the fault codes.  Not all this may be related to the cooling problem but I'm otherwise out of ideas.

I am currently clueless.  

neonowner23 neonowner23
New User | Posts: 7 | Joined: 02/10
Posted: 07/22/10
09:11 AM

I guess I should add that when I remove the radiator cap when the engine is cold (and running), there are little bubbles that come up in the coolant through where the thermostat is.  I am worried, as worst case scenario, this is exhaust gas being blown into the coolant.  A blown head gasket is pretty expensive.  

thatguy702 thatguy702
New User | Posts: 9 | Joined: 07/10
Posted: 07/22/10
10:18 PM

Just because you don't visible see a leak, doesn't mean there is one. You need to pressure test it with a pressure tester. If you aren't filling the coolant every two days, then I bet we can say there is no leak. First check the fins on the radiator, there may be dirt clogging the radiator, not allowing air flow. Next, they have block testers the can see if there is exhaust in the coolant, but you need the special tester. This would tell you if the head gasket is blown. When the car over heats the a/c cuts out, its default. Its sucks even more when its 100+F outside.  
It was like that when I got here!

neonowner23 neonowner23
New User | Posts: 7 | Joined: 02/10
Posted: 08/03/10
07:51 PM

A mechanic in town told me to check the fins too.  In places where big bugs smash the fins or clog it this can be a problem.  In my case, it is not.  I sprayed out the cooling fins and examined them.

I finally got a hard (meaning it comes on after being reset) check engine light for the camshaft position sensor.  If I unplugged the sensor, it had the same crappy 5 second crank at start-up.  I checked the voltage and ground at the sensor to ensure it isn't a wiring problem.  I replaced the camshaft position sensor.  My car didn't overheat and started fine on a 150 mile drive I did today.  I'm assuming because the sensor was bad, there was default timing set by the computer.  I heard that if the timing is off, the engine can run hot.  That would explain the cooling problem.

Because the car has 90k miles on it, I replaced the timing belt and water pump.  I figured there may be a loose impeller or something on the pump and took advantage of the scheduled timing belt change to check it.  The old water pump was in perfect shape.

Thanks for the help.
In my mind the internet is like the Wizard of Oz.  Ask and you shall receive.  

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