2003 Neon overheats after replacing... everything

My 2003 Dodge Neon started overheating. We replaced the thermostat, temperature sending unit, flushed the radiator, checked for blockages, cleaned the radiator, changed the head gasket and water pump.
It can run for about 10-15 minutes driving or 30 minutes idling before it overheats. The fans will kick on. The thermostat opens up. Pressure builds up on the radiator hose. When it gets hot, it boils back into the reservoir.
I’ve been careful not to let it get into the red since the head gasket change.
We sent the head off and had it planed. Shouldn’t they have checked it for cracks, too?
Any other ideas besides a cracked head?

Radiator plugged up or the cooling fins in the core are plugged with debris or they have corroded away…Solution: replace radiator.

Water pump impeller corroded / failed. Solution: Replace water pump.

A good flow test: Remove the thermostat. Replace the upper hose on the block. Remove it from the radiator. Start the engine and goose it a little. Water should shoot out of the upper hose with considerable force…If flow is weak, determine why…

When you installed the head bolts and torqued them, did you apply a thread sealant to the threads so the proper torque was reached, and to prevent any leaks from occurring from between the block and the head?


You didn’t replace the most important part. The 03 Neon. Sorry I just had too. :wink:

Well, you haven’t replaced the radiator cap yet–if the cap is weak the system won’t hold enough pressure to cool efficiently.

I would also have a test done for combustion gases in the coolant. This will tell you if you have a cracked head or something went wrong with the head gasket replacement.

You can get a test kit at almost any parts store to check for combustion gasses in the coolant.


hmmm … it seems like you’ve done pretty much everything possible, yet it still overheats? This is a true puzzler …

I guess if I had this problem, given all you’ve done to date, first thing I’d do is replace the radiator. That’s not a very difficult job, and new aftermarket radiators come pretty cheap these days. And they usually come with a new cap too. When I replaced the radiator in my Corolla, the new aftermarket radiator cost less than $100, and was simple as pie to install. And it works like a charm.

If that didn’t fix it I’d do some of the tests as posted above to see if the head gasket repair didn’t take. Or if you have a crack in the head or block. Besides those, a shop could do cylinder leak down tests and cooling system pressure tests.

Should the head re-surface place have checked for cracks in the head? I’m not sure if they do this as a matter of course. Machine shops do have sophisticated methods to check for tiny cracks and imperfections in the head, but you may have to ask for that service at the time.

If you feel lucky you might try just replacing the radiator cap as oblivion mentions above. It seems sort of crazy, but if the radiator cap is on the fritz and doesn’t set the correct cooling system pressure, the engine will overheat pretty much no matter what else you do.

Replaced the radiator cap. Didn’t help.
If I test for combustion gases, would it detect residual traces from when the head gasket blew? I’m worried it would give me a false positive, meaning it shows I had a blown head gasket but would in fact just be left over from the last time. Would that detect a cracked head as well?

I hate to see you work all week for nothing but I don’t mind suggesting that you work for a few minutes for nothing. On a car radiator, mostly on the back side, if about 5% of the fins are rusted away, the radiator won’t work very well. After ten minutes all bets are off, especially if you live in a hilly area. Sometimes you have to pull the shroud back to look at the areas that it usually covers up.

Just on the off chance. The fans are running in the right direction …right???

If you test for combustion gasses it will detect the gasses from before the head job, unless you flushed the block and radiator good and changed the coolant.