Hi, Our '96 SOC holds the mid-range on the temp guage until the air temp hits the low 90's, when it slowly creeps up to the top of the scale. Turning on the heater can reliably bring the temp back to center. It behaves as if the engine is marginally short of cooling capacity.

I know no history on the car other than a head gasket repair or engine transplant was likely done in the not too distant past. I've confirmed that both radiator fans are working properly, there is no air in the cooling system, coolant is topped up, and there are no obvious air flow restrictions at the radiator.

I suppose it could be headgasket related, but the fact that the car behaves normally at ambients below 90F makes me hopeful that this is not the case. I'll check the flow at the thermostat tomorrow when the engine is cool.

Any suggestions on what else may likely be causing these symptoms? Are the Neon radiators especially subject to external or interal corrosion that could block air or water flow? If so, can DIY flushing or a radiator shop fix this - or must they just be replaced?

Thanks and regards, Bob

 

First, try going to a do-it-yourself car wash and pop the hood. While it is running, blast the water through the radiator fins from the front to help clean out any dirt or debris that may be plugging it and blocking air from passing through it. If this doesn't solve the problem, then a radiator power flush at a shop would be the next thing to do. If neither of these solve the problem then it is either time for a new thermostat or radiator. The only thing left after that is the engine/head/headgasket.

 

I would say the thermostat is not opening up

 

Power washing the radiator and a new thermostat didn't remedy the problem. Will try a new pressure cap and double check the temp sensor before pulling the radiator.

One puzzling thing is that there is no coolant overflow even when the gauge pegs at the top end. Anyone know if the Neon expansion tank usually overflows if the engine really does max out as the temp guage shows? My last hope for a simple solution (other than the cap) is that it's the temp sender rather than the cooling system that's marginal. Though I suspect I'll most likely be pulling the radiator this weekend.

Thanks!

 

FYI - Cause of the marginal cooling turned out to be the 100% concentration of antifreeze put in the car while it was in New Hampshire - thought it looked awful green [sm=smiley29.gif]. Manual calls for coolant concentration in the 50 to 70% range. Was probably never a problem up north, but not so past May in Louisiana and Texas.

We're nipping at 100F ambient and the problem is gone with 100% water. I'll go to a 50/50 mix once I get the new radiator in. Found a bit of seepage at the bottom tank while inspecting the cooling system, so decided to go ahead an replace the radiator anyway.

 

Yeah that'll do that. Water has good cooling properties, in fact running 100% water in the summer would be ideal if it wouldn't cause rusting and corrosion. You add antifreeze for two reasons, first is the obvious one which is to keep it from freezing in the winter, second is to raise the boiling point of the mixture and to inhibit corrosion. That is why they recommend a 50/50 mix year round, you get the best of both.[sm=smiley20.gif][sm=smiley2.gif]