WTH thread: overheating... but not missing any water?

Darkness · Post by **Darkness** » Sun Mar 10, 2013 12:35 pm

My girlfriend has been driving our trusty (as in, we can trust it to come up with some random repair at the least convenient times) Neon for several years. This is a 2001 SE, 5 spd, zero options.

I've replaced the radiator a couple of years ago and had no problems with the cooling system until recently. The car started to run hot and stink like coolant, so I checked the radiator and found it was down. I refilled it. This happened a couple of times so I figured it was coming up on "replace the water pump" time, until I noticed that the overfill bottle was full to the line, exactly where I had left it when I replaced the radiator two years ago.

I then figured it was either the cap or the t-stat, so I bought both. I replaced the cap first (since its the easiest and I'm lazy) and the problem went away.

Now heres the new problem, and the meaning behind today's thread title. Yesterday, she called me to say that the temp had started to climb while she was cruising on the interstate. She pulled off the superslab and into a parking lot, and the needle shot into the red, the cluster went crazy and chimes went off. She turned the car off, heard a loud >pop< like (quoting her) "popping a plastic bag". Then steam rose from under the hood and the radiator stink was everywhere.

She had it towed to a local "U-Bring It, We Screw U" shop, and even though she fit the complete description of an easy mark ("Panicked girl with cash, and has no clue how to describe any work thats been done on the car or even what just happened") they said that they found nothing to repair on the car, and none of the fluid levels were depleted including the radiator. They charged her diagnostic time, and as if they actually felt bad, they did a reverse coolant flush for her. We're going to get the car back this afternoon, for $80.

So... WTH happened? Was that loud pop the thermostat opening suddenly? Is there some kind of malignant air pocket roaming around this motor like a bully prowling school hallways?

Oh... she just told me that she heard "chirps" yesterday, like a loose belt. But the belts have been replaced. That sounds like a water pump going to me.

Theres a lot of people here with a lot more experience than me with these cars, so advice on what to check would be great. If I have to change the water pump, the Haynes book is absolutely useless, picturewise. Are there any good DIYs you can recommend?

Post by **occasional demons** » Wed Mar 20, 2013 9:52 pm

If you can smell coolant, it is going somewhere. A bad cap might have been why it was not pulling coolant from the expansion tank. A cracked hose from the water neck to the tank will also not let it pull coolant back into the system.

Since it was not pulling coolant back, there may have been air trapped in the head. It should have been eventually purged out if the cap and expansion tank are working properly. The air should have been vented to the tank, and when the engine cooled after parking, it should have drawn coolant back to replace the air.

The "pop" is anyone's guess. How many miles? The timing belt and water pump are generally replaced together, along with the timing tensioner. 105,000 miles is the recommended interval.

A 1gn, but most likely, you have this style tensioner.
http://jball.neons.org//howto/timing_belt/howto.html

The better one for a 2gn.
http://chronoscender.freeservers.com/ne ... gbelt.html

Edit:

AutoZone rents a nice puller for the crank pulley. ($75, but you get a refund when returned)

I use chain Vise Grips to hold the cam sprocket. They work very well. You just need to brace them against something when torquing the cam bolt.
I recommend pulling the valve cover, you probably need a gasket anyways, and loosening the rocker shafts so you don't bend any valves, either tightening the sprocket, or timing the engine.

Vise Grips are about $25 to $30. You might be able to rent a torque wrench from AutoZone also. You can get a timing component kit from www.rockauto.com for a reasonable price. I would go with the 2004 liten's tensioner. But like the link shows, you need to modify the rear timing cover. Very easy to do.

ducktapetg · Post by **ducktapetg** » Thu Mar 21, 2013 8:36 am

The rad. fans turning on? My 1st gen over heated once because the sensor connection got corroded. Granted, I didn't hear a pop or chirping but chirping could also be an accessory belt. I am no expert but it might be worth looking into prior to ripping into it.

Darkness · Post by **Darkness** » Thu Mar 21, 2013 11:11 pm

occasional demons wrote:If you can smell coolant, it is going somewhere. A bad cap might have been why it was not pulling coolant from the expansion tank. A cracked hose from the water neck to the tank will also not let it pull coolant back into the system.

Since it was not pulling coolant back, there may have been air trapped in the head. It should have been eventually purged out if the cap and expansion tank are working properly. The air should have been vented to the tank, and when the engine cooled after parking, it should have drawn coolant back to replace the air.

The "pop" is anyone's guess. How many miles? The timing belt and water pump are generally replaced together, along with the timing tensioner. 105,000 miles is the recommended interval.

Something like 160k on this car, and climbing about 70 miles a day. Its our workhorse commuter car. The belt was replaced last year, just in time as it was ready to come apart. Someone told me that the pop was probably the spring in the radiator cap, like the thing had jammed shut and suddenly opened. Sounds silly to me.

I think this motor is ready to give up the ghost. Whats a decent salvage pull 2.0 going for these days? I don't see any available on the local Craigslist for comparison.

ducktapetg wrote:The rad. fans turning on? My 1st gen over heated once because the sensor connection got corroded. Granted, I didn't hear a pop or chirping but chirping could also be an accessory belt. I am no expert but it might be worth looking into prior to ripping into it.

The fan thing sounds like a possibility except the temp started climbing when she was on the highway, not in stop and go traffic. That to me says "no coolant flow", which is either generally a water pump failure, or as our moderator said in the post above, an air bubble in the water jacket.

Post by **occasional demons** » Fri Mar 22, 2013 8:46 am

The WP is something that should have been replaced with the belt. I would do/have done a compression test, and a cooling system pressure test before scrapping the engine.

If the WP seizes, you are as good off as a broken timing belt.

You are looking at 1996 to 2002 engines for the easiest replacement. The 1995 has a different block, but will work with some modifications. The 2003 -up will not work .
You can also use the 1995 to 1999 DOHC bottom end with your SOHC head, if you wish to keep it SOHC. The 1996 - up sohc used the same block as the 1995 -1999 DOHC.

Usually, the 2002 -older 2,0's are more expensive.

Darkness · Post by **Darkness** » Fri Mar 22, 2013 10:58 pm

Don't know about the water pump, but the cooling system was pressure tested by the shop that handled the aftermath of the overheating event. They said it was fine - after they ran two complete flushes and got all the nasty out of it.

Compression test, I'll have to see if I can run that this weekend. I was thinking about doing it anyway.

I took the car to work this morning. I noticed a faint knock that went away within 10-20 seconds. It wasn't regular like a rod knock, but random. I asked her what oil weight the shop was putting in there, and she said it was 10/30 high mileage oil. I think it should have been switched to 10/40 a long time ago. Unfortunately the SE doesn't have an oil pressure gauge and I don't feel like wasting $100 putting a gauge in the car.