They don't catch a lot of air so the radiator flow has to be nearly perfect. I suggest you drain and pull the radiator then have a radiator shop test it. They can tell you if it's clogged. That's where I'd start after all the other work. Radiators can clog as the fluid breaks down. When (or ever) was the last time the reservoir was cleaned? Generally people skip over them. Often you'll find a layer of thick green sludge on the bottom. Which gets cycled/pulled into the system during normal operation.
I run it up on ramps to purge the air from the system. Let it idle with the cap off for a half hour. That should burp it for you.
Also, and you may already know this, do not tap water in the radiator. Even when flushing the system. Use distilled or demineralized water as a mix with the coolant. Or use the 50/50 premixed stuff.
You may want to slap new hoses on when you pull the radiator.
Love those Neon's, nothing easy to get at or work on...
The radiator itself could be the issue or it could be improper flow of coolant through the system ( such as a collapsed or blocked hose for example ).
Whomever replaced the coolant should have bled the air out of the system at that time but yes, air pockets in the cooling system can be the issue as well.
The strangest thing I ever saw, that caused a car to overheat was trash in between the ac condenser coil and the radiator. The air couldn't flow through the rad. Because a blanket of dirt and paper had collected on the front of it. The strangest thing I ever heard that caused this to happen was left over clay like material in the block, that stopped the water from circulating in the motor. I was told it was part of the clay mold used to cast the motor. That wasn't flushed out by factory workers.
Hi lets face a few facts here a 10 year old car hoses collapse when they get hot so they could be an issue radiator core could be a bit furred up by now or have a leak.
the leak would mean it is not getting up to working temperature which is most pressurised coolant systems is 122 degrees C. so there is still a load of parts to consider when this occurs.
if this an ongoing problem even after these types of repairs it isnt air in the system.. look at the radiator itself it may be blocked or damaged. it is out of sorts for a four banger at higher speeds to have this issue but if everything else is fine or replaced then the radiator is next. you also noted this has been happening for awhile.. check the oil if it looks foamy or whiteish they warped the heads..
Clogged or blocked radiator. Coolant hose(s) collapsed internally. That's a couple for you.
The cooling system needs to be drained, flushed and CLEANED!
My friend has been having overheating problems for the past few months. The system has been flushed and new coolant. She has also replaced the water pump, thermostat, and the radiator cap. It tends to only overheat at constant highway speeds 60+. I want to think that she has air caught in the radiator. Any other suggestions to check?
