I purchased this 96 sohc from a mechanic who was selling it for a customer of his and said he was real familiar with the car and would make a great car for my college daughter. Hey, the guy owns a shop, so i pretty much test drove it a few miles and was impressed with the shape it was in and really trusted this guys familiarality with the car with 92000. ok, the daughter drives a 60 mile cruise with it after the purchase and it goes dead a block from the house. I am since out of town and call the guy who sold it to me and he says to tow it to his shop and he will reluctantly look at it. well , he cant find the problem of blowing the fuel fuse and writes it off to a bad and old fuse. Hey, I trusted this shop owner. She luckily got 500 miles down the road back to campus in Las Vegas before the same dead in the water neon acted up again. Towed to a garage, we were buffaloed into thinking these guys were not only tow truck drivers but mechanics also. Well, having suggested over the telephone that rather than replacing the fuel pump why dont we first look at something electrical. 3 weeks later, and biting my tonque with every ecuse these quys gave me about how they are stumped, I finally was able to get there to settle up just knowing what i was their excuse for a sorry *** garage . I forked over the $1200 the outfit demanded after they told me the neon has some serious problems that they discovered the past 3 wks working on it nite and day. Besides a melted fuse box, and some chaffed wires handed to me on my way out, they assured me that a free tow was just a call away...I transported this neon home, and while in the driveway took a quick look at this money pit. Within five minutes,we fixed the electrical problem that left my poor daughter and her neglected neon at the side of the road about five times. How about a wire under the fuse box that lacked 4 inches of insulation. A 1200 dollar repair fixed in five minutes. Besides the good service we recieved, they gave us back the little neon with a serious overheating problem. I will cut to the chase and perhaps someone can diagnose the problem before i do a head gasket job.
1. A new thermostat was not the answer
2 She gets hot whenever she wants and gives no warning, sometimes going as far as 100 miles.
3 I am going to start with the easy replacements first, Temperature sensor? Water pump? Purge the radiator? What....help

 

the first thing i could suggest is to make sure it has proper coolant and level in it, than check that the radiator is full and that there is no air bubbles in the system, since you said the thermostat was replaced they might not have properly bled air out of the cooling system. some cars have a bleeder at the highest point and other the radiator cap is the highest point. Then check the thermostat, one method is to boil some water and get it around the temp in which the thermostat should open, and drop the thermostat in to the water, if it opens than the thermostat is in good working condition.

Let me know what you find

 

Ive had that problem before. Being as thoug the car is a 96 there is a good chance I needs a new water pump. I had this exact problem your describing. After replacing the pump it never happened again. Neons are some of the best cars out ther, they have their problems like all others, youve just had them one right after the other. Check the water pump, if not that then go for the radiatior. But before you take this advice if you do, do what Charles says and check the coolant levels and the thermostat. A new pump isnt too terribly expnsive, especially off ebay. Good luck dude. Hope everything works out.

 

The biggest cause of overheating is a leak somewhere. It could be a coolant leak out of the system, an air leak into the system, or a combination of both. For the neon, the biggest offender is the infamous rad cap. When you turn off the car and the coolant starts to cool down, it draws a vacuum. Normally, makeup water from the overflow tank would come in. But if the cap seal is letting air by, it's much easier to draw in air than water... Then when you start the car back up, the air gets circulated through the system. Since air (or steam for that matter) is not a particularly good conductor of heat, portions of your system can get extremely hot if that bubble gets trapped (i.e. thermostat closed). Then when it gets rewetted, that heat transfers very quickly to the coolant, and when that slug of coolant gets around to the temp sensor, it spikes.

This is also where the "bubbling coolant syndrome" comes from. Immediately after shutting the car off, some of the air will get back up to the top of the system, and since the coolant is still drawing heat from the engine, temperature (and pressure) are rising. This forces the air out into the overflow tank, making a boiling sound. Problem is, not all of the air makes it to the top, and then more air gets sucked back in once the temp starts dropping...

Then there are fouled radiators. Folks that put regular tap water in their coolant systems are just asking for trouble. Tap water still contains plenty of salts and minerals, all of which are happy to plate out at temps higher than 160F or so. The tiny passages in your radiator don't take that long to start getting clogged. Less flow through the rad, less cooling.

Next up would be the rad fan(s). Some Neons have one, most have two. The PCM should turn them on when coolant temp reaches 220F or so, and turn them off around 200F. Also, they should turn on automatically any time the a/c (including defrost) is turned on. If this isn't happening, you'll notice overheating more in town and short distance driving rather than on long freeway trips where moving through the air at 75 mph gets quite a bit of airflow through the radiator. There is a fan fuse and a fan relay in the box under the hood behind the battery. The relays are switchable with any of the others, I tend to use the horn relay for testing... Fuses are the common smaller type. And there's the off chance that some wiring along the way is getting rubbed/pulled and shorting out.

All the connections should be thoroughly checked. Cracked hoses, collapsed hoses, and failing hose clamps do happen.

Pinhole leaks can be a nightmare to track down, particularly with the radiator still on the car... I finally found the leak on my last rad after taking it off, taping over the big holes, and dunking it in the bathtub until I found the air coming out... I could smell it, I could see drips of coolant after a long trip, couldn't see the leak on the car for anything. Forget the stop-leak crap, I've found they only make matters worse (not this car).

There's also the famous Neon head gasket issue. Yours is a '96, built before the "upgrade". There's a slim chance that you have the new gasket in there already. If you look down between the intake manifold runners #1 & #2 (where the oil dipstick is), where the head meets the block, there should be a metal tab sticking out if you have the updated head gasket. If you don't... You can pick up the parts you need for a compression test for $25 or so. A leakdown test requires an air compressor, I've never bothered. The kit should come with instructions, but ask if you need to. Pressure should be 180 psi in each cylinder, but isn't really a problem unless down below 150-160 psi. The real problem is if they aren't all the same, or pretty close to it. If you put a little motor oil in the cylinder and run the test again and pressure still doesn't come up, it's time to start thinking about the head gasket. Other big clues are murky coolant (oil in the coolant), water in the oil, or white smoke coming out of the tailpipe that smells remarkably like antifreeze.

The factory water pump is only designed for a 105k mile service life, same as the timing belt. you've still got a ways to go, but overheating will shorten that life... I certainly wouldn't peg the water pump as the most likely cause, and I wouldn't recommend it as a first line of attack. But you are getting close to that point, so if all else fails...

So here's my suggestions, if the first one doesn't work, on to the next:
- Turn on the car, let it warm up for a few minutes, turn on the a/c. If the fans don't come on, start there...

- Check all the connections thoroughly. Hose clamps aren't really that expensive, consider replacing the ones on there. If you have any doubts as to the condition of the hoses, replace them.

- Buy a new radiator cap. Top off the system and overflow bottle (halfway between fill and full) with premixed coolant (engine cold). Start the car with the cap off and wait for the thermostat to open (195F). You should see plenty of flow. If level drops (air in the system), top off again (thermostat should close immediately when you do this). Keep going until the thermostat opening doesn't result in a level drop or the fans come on (really getting hot now...). Keep a bucket under the car to catch any overflow (there will be eventually). And when you shut off the car, keep an eye on level, you'll need ot top off a little as the system cools down before putting the cap back on. It usually takes me about 3 tries when I do this before I'm satisfied. If you are unsure about the quality of coolant already in there, go ahead and drain/refill before starting... I replace my rad cap every other oil cahnge, which may be a bit overkill. Then again, most people don't have ~240k miles on their car...

- Drain the system and remove the radiator from the car. You can check it yourself in your own tub (spouses don't like this idea for whatever reason...), or take it to a shop and have them leak check it for $30 or so. The Neon's stock radiator is a copper core, plastic end bell setup. It is fairly cheap and not a quality piece of work. It is absolutely not worth plugging, welding or otherwise fixing. Whatever you fix now will happen again in a few months in another location... http://www.coolradiator.com/HPAPDodgeNeon2.htm has an aluminum core (still plastic end bells) unit for only $149 shipped. That's cheaper than a crappy copper core replacement anywhere. I went this way for my third radiator and absolutely love it.

- Compression test. Do it yourself, or take it to a shop and have them do a leakdown test as well. This will let you know if you need to do a head gasket. If you need to do a head gasket, you're going to have the timing belt off anyways. So...

- Timing belt and water pump replacement. It's expensive if done at a shop ($500-700+ easily). www.boogerracing.com has a spectacular how-to on timing belt replacement for the SOHC. I don't recall if he did the water pump in that job, but it's right there (driven by the timing belt) and easy to do. Doing it yourself would run $50 for the belt, $50 for the pump, $20 for the gear puller you'll need to get the crank pulley off (or rent it for free at Autozone) and $15 for the Miller Special Tool insert you'll need (or use the big 12mm stock passenger side motor mount bolt for free... carefully...). If you're really adventurous (or paranoid like me), the tensioner is another $50 or so.