99 Dodge Neon

I have a 99 Dodge Neon which recently started exhibiting some bizarre
behavior. Originally I had to replace the radiator due to corrosion.
So I got a new aftermarket radiator, new hoses, thermostat, replaced
everything, filled her up with 50/50, ran the car until all the
bubbles dissapeared, topped it off a little bit more. Car ran fine for
awhile.

Now the bizzare stuff. Like clockwork the car will intermittently
overheat after running (under load or just idling). 2 minutes or so
after first starting the car and just normal driving the seat belt
alarm will come on for about 10 seconds then go off, 3 or 4 minutes
into driving the radio will "blank out" for about 4 to 6 seconds then
come back on, interior and exterior lights will periodically dim, and
most importantly - 10 minutes or so after having reached operating
temperature (about 1/3 up on temp gauge) the car will overheat.
This is not a runaway overheat condition. The temperature gauge will
suddenly max out, the audible alarm will sound then after a few
seconds (10 to 20) it will back down again. Then it will
intermittently repeat all of the above from the seat belt alarm down
to the temp maxing out again. It will continue doing this until I turn
off the engine. It will repeat everything the next day after having
sit overnight or just a few hours.
When the temp maxes out I turn on the heat inside the car to help it
shed some heat. It helps back down the temp gauge and it will
fluctuate around middle then max out again for a few seconds
periodically.
I have checked the fan fuse (fuse ok). The fans work though I believe
they may come on too late at times. I have replaced the temperature
sensor/sender in the head. All coolant levels are normal. The
reservoir is always half full. There is no coolant in the oil so that
rules out a cracked head or head gasket. Is the computer bad? Or could
it be a relay somewhere that's bad? I've spent hundreds on this car
and no mechanic has able to properly diagnose this problem so far.
Anybody have any ideas?? Thanks in advance.

I forgot to mention I have checked and confirmed coolant is
circulating. Taking the cap off, starting the engine cold until it
reaches operating temp reveals thermostat does open when it should and
coolant is flowing properly. A mechanic also confirmed and ruled out
the water pump.

On Sun, 30 Oct 2005 23:20:17 -0500, alienvamp.RemoveThis@mars.com wrote:

>I have a 99 Dodge Neon which recently started exhibiting some bizarre
>behavior. Originally I had to replace the radiator due to corrosion.
>So I got a new aftermarket radiator, new hoses, thermostat, replaced
>everything, filled her up with 50/50, ran the car until all the
>bubbles dissapeared, topped it off a little bit more. Car ran fine for
>awhile.
>
>Now the bizzare stuff. Like clockwork the car will intermittently
>overheat after running (under load or just idling). 2 minutes or so
>after first starting the car and just normal driving the seat belt
>alarm will come on for about 10 seconds then go off, 3 or 4 minutes
>into driving the radio will "blank out" for about 4 to 6 seconds then
>come back on, interior and exterior lights will periodically dim, and
>most importantly - 10 minutes or so after having reached operating
>temperature (about 1/3 up on temp gauge) the car will overheat.
>This is not a runaway overheat condition. The temperature gauge will
>suddenly max out, the audible alarm will sound then after a few
>seconds (10 to 20) it will back down again. Then it will
>intermittently repeat all of the above from the seat belt alarm down
>to the temp maxing out again. It will continue doing this until I turn
>off the engine. It will repeat everything the next day after having
>sit overnight or just a few hours.
>When the temp maxes out I turn on the heat inside the car to help it
>shed some heat. It helps back down the temp gauge and it will
>fluctuate around middle then max out again for a few seconds
>periodically.
>I have checked the fan fuse (fuse ok). The fans work though I believe
>they may come on too late at times. I have replaced the temperature
>sensor/sender in the head. All coolant levels are normal. The
>reservoir is always half full. There is no coolant in the oil so that
>rules out a cracked head or head gasket. Is the computer bad? Or could
>it be a relay somewhere that's bad? I've spent hundreds on this car
>and no mechanic has able to properly diagnose this problem so far.
>Anybody have any ideas?? Thanks in advance.