97 SOHC neon overheat issue

[JohnnyIroc]

recently picked this neon up, owner said he has had it for a year and the day he got it that it overheated on him and he changed the radiator and put a new thermostat new hoses and all on it and that he has not had an issue after
well ive been daily driving it the last 2 weeks with no issue untill tonight
drove all over today, highway and city mix all day no issues whatsoever
just at the end of the night i run up to a buddys house and as im about to pull in his driveway the thing peggs up and then starts beeping
i shut it down, pop the hood no signs of anything being hot, im able the touch the radiator no problem lots of pressure in the hoses
well i let it cool a bit, start it back up shows a little hotter then normal i pop the rad cap as its running, it shoots back down to normal, i go to take it on a drive and when i drive like i normally do shifting around 2k RPM it stays around normal maybe a little hot, but if i consistantly shift at about 3k or maybe more it starts to really get hot quick
what can it be

[black86glhs]

Bad temp sending unit?

[JohnnyIroc]

was going to change that tomorrow along with a manual gauge

[RoadWarrior222]

Seems like the waterpumps can do a silent fail, where the impeller is loose on the shaft or something and they don't push much. Additionally there's a problem in the dash where solder joints go bad and the gauge pegs when there's nothing wrong.

Also related to the pump is that they can weep out the seal, slowly enough that it evaporates off the side of the motor and you never see the leak, but this seems to put airlocks inside the head quickly which disturb flow, and can be a bugger to burp out and make sure it is actually full and flowing.

So if you turn the heater on fulll blast and heater output is erratic then suspect a flow problem either due to pump failing to turn or because it has airlocked the system from weeping. If it heats evenly and the gauge doesn't move, try thumping the dash.

[RoadWarrior222]

Oh, it could be a headgasket leak too, either internal to the cylinders or external, inspect carefully, sniff the exhaust, get a testing kit or make limewater and bubble gas from rad cap through it. If it's a slight external leak, which is not hitting the ground, but still getting air in, look for suspiciously clean spots... buggers can valve under load, i.e. not leak until you're going down the highway at 3000 RPM ... coz there's just that much stretch in the bolt or something, and needs just that much coolant pressure, so until it gets the right cylinder pressure and coolant pressure it appears fine... and free revving it often won't do it, because of no load... they usually fail more obviously after a few hundred miles like that though... but bars leaks or something can seal it up.

[Dony409]

I had a 98 that I bought cause the guy said he replaced the rad thermostat all the hoses and the water pump and it didn't make any difference... I absolutely bagged this car and the temp would be normal and then suddenly rocket up and start beeping and then a little later It just dropped back down... I believe it es something electronic cause it never boiled over or anything... The other thing could be a bad cap but that wouldn't make the gauge rocket up

[JohnnyIroc]

thanks roadwarrior for all the help, the next day after sitting the cylinders where full of coolant
pulled it apart did mls headgasket with copper spray water pump and t belt,
got it back togeather last night
it drives great holds temp great
only wierd thing is on startup its fine and when driving its fine
but if left at idle for a bit it will smoke out the pipe a bit
i hear all over coolant gets clogged up in the cat and muffler real good
but to only be smoking after idling for a little while is kinda strange
any idea?

[Juggy]

what color is the smoke??
if its white i wouldnt worry about it. prolly some leftover antifreeze burning off through the exahust. give it a few days and it should dissipate

[RoadWarrior222]

Yah, the cat might need a couple of longer runs (30 mins of highway) to clear out good. Also could be a tad rich if the O2 sensor got drenched, and that too should clear up with some running around.

However, if very blue/oily could be that the PCV valve is bad, or the pcv hoses are sucking flat or collapsing internally when they get warmer and softer... check those... if that's not it, it could be that the valve stem seals are on their way out... but a good "high mileage" oil can plump them up and keep them going for years. Pennzoil and Castrol versions work best in my 3.0

[contraption22]

Are the fans comming on?

[JohnnyIroc]

Yah, the cat might need a couple of longer runs (30 mins of highway) to clear out good. Also could be a tad rich if the O2 sensor got drenched, and that too should clear up with some running around.

However, if very blue/oily could be that the PCV valve is bad, or the pcv hoses are sucking flat or collapsing internally when they get warmer and softer... check those... if that's not it, it could be that the valve stem seals are on their way out... but a good "high mileage" oil can plump them up and keep them going for years. Pennzoil and Castrol versions work best in my 3.0
haven't seen any smoke yet today
i checked the pcv while it was apart it was good, and i had to replace the pcv hose with parts store crap because it cracked
also have cheap mobil 5k in it now as a clean out oil, so i will put in a high mileage now

Are the fans comming on?

yes fans kick on and off regularly

and the smoke was white

[looneytuner]

Re: 97 SOHC neon overheat issue

Seems like the waterpumps can do a silent fail, where the impeller is loose on the shaft or something and they don't push much. Additionally there's a problem in the dash where solder joints go bad and the gauge pegs when there's nothing wrong.

That's what happened to me. Except it didn't overheat. It seized up, took out the belt, and bent the valves on a 96 DOHC.