I just bought a non running 99 Neon RT for cheap last week. Replaced the camshaft position sensor and it fired right up (timing is also good). The car overheated when I tried to drive it. The car heated to its normal temp and then started to climb until it finally jumped to the top and the car started dinging to let me know.
I have since replaced the thermostat and the coolant temp sensor. Car still overheats when I drive it and it did eventually overheated when I let it idle in my driveway. When it was idling in my driveway I checked the fans and they were on and spinning when it overheated so the fans seem to be working. I also tried to get any air out of the coolant system by running it on an incline with the rad cap off. So the fans are working as far as I can tell and the upper rad hose has flowing water in it so thermostat is opening correctly. What could this overheating issue be? Water pump? Any help? Thanks.

 

Blocked coolant flow. Air in system. Faulty temp gauge. Head gasket.

Check th oil and the coolant res to see if these fluids are mixing. Alos check the lower radiarot hose for any recent wetness/leaks.

 

Could be a bad radiator as well.

 

It's not a faulty gauge because when I turn the car off when overheating the coolant is bubbling and I eventually lose coolant through the reservoir overflow. Besides when it overflows from the reservoir, it does not leak at all. Not one drip of coolant while driving, idling, or when off unless overheating and overflowing from reservoir. No water in the oil or oil in the coolant and no leaks means its probably not the head gasket... right?

I am in the process of replacing the water pump. If that does not fix it I will look at the radiator next and have the system flushed. From this info, what is the most likely culprit or in what order would you guys check things out if you were having this problem? Thanks!

 

Well the only way it is going to be the water pump is if all the fins are gone off of the pump and I do not see that happening. I am guessing you still have air in the system somewhere, and sometimes it can take some doing on getting it out. When I did my car, geting the air out of the system took awhile. I ran it with the cap off, I ran it with the cap on. I went back and fourth from the two untill I was sure that all the air was out.

 

I figured the water pump could break where the belt still turns the outside and the fins don't turn or barely turn like a clutch disengaging. I don't know if the pump has like a bearing between the two sides that could go bad or if it's solid and the fins have to spin when the belt drives it. I didn't know so I thought I would replace it.

I'm having a lot of trouble trying to get the crank pulley off. My local autoparts store has a pulley puller where the bolt wants to thread in because it is on so tight. I will hopefully get it tomorrow by welding a heavy duty washer onto the pulley puller so it can't thread in. Huge pain in the neck and 2 days trying to get it off.

Should I just have the coolant system flushed to be sure there is no air in it? Don't know how much it costs, but would it be worth it to be sure or just do it the longer and cost free way?

 

If you are changing the water pump, might as well change the timing belt and idler pulley while you are it too (every 100,000 miles).

You can use the side mount bolt (you will have to support the engine) as an insert to get the pulley off.

 

yeah that pully can be a pain but if you have ever pulled as many off as I have it is worth it to get the blu- point puller. takes me about 10 seconds to get it off.

 

Where do you get that puller? I just broke a brand new 3-jaw puller from Autozone.

 

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