We have a 2001 Neon that my son drives. Base model 4 door. I have replaced the fan assembly, radiator, thermostat,radiator cap and we still have the issue.

We drove the car for about an hour, no issues. On the hour drive home, about two miles from the house, the temps started to hit the "hot" mark on the gauge. Then it slowly went back down. Water is topped off, haven't lost any that I can tell.

I did order a new temp sending unit and another thermostat to swap as a "just in case". I also bought a new fan relay, but I can't find it to replace it yet.

Any info on where the fan relay is? Any advice will be appreciated.

 

Welcome to the 2nd Gen Neon forum.

Lets think about the fan relay question some more. If your wondering if the relay is working to turn the radiator fan on, just turn the A/C on & raise the hood to see if the fan is running. If it is, the fan relay is working. The fan power relay is located in the under hood power distribution box, drivers side, in front of the shock strut tower & the lid inside will id which is the fan relay.
If your in doubt about the fan relay, before buying another, to test, try swapping it out for a like one not needed to run the engine & see how it goes.

On the intermittent overheat indication, until you get it fixed, when test driving & it's indicating a over heat condition is happening, or about to happen, roll the windows down, turn the in cabin Heat Temp control & fan speed to Max & it'll help cool the engine down, so you don't warp something important.

If we're moving say 30mph or faster, we should have enough air flow through the radiator to keep the engine cool, even if the fan isn't working.

You might consider having your favorite auto parts store perform their no cost cooling system pressure check, to determine if all is tight internally.
Also have them test the pressure cap to make sure it's holding pressure. If you have to buy another one, have it pressure checked Before leaving the store with it.

When you refilled the cooling system, did you have the front end raised, or facing Uphill, the steeper the better, so to chase entrapped air toward the radiator so it could burp.
Then after it was refilled, did you mark the over flow tank coolant level, start the engine, turn the heat temp control to Max, & let the engine warm up until the thermostat opened/top radiator hose was Hot, then run it at say 2500 rpm for 5 min or so, to help chase any remaining air bubbles toward the radiator?

Then let it fully cool down with the front end raised & hood up, so it'll cool faster & then recheck the recovery tank to see if the coolant level dropped?
If it did, the system had burped a slug of air, so top up the recovery tank & perform the warm up/cool down proceedure again until the recovery tank level ceases to drop. Then the system should be fully burped of air.

EDIT: Did the replacement thermostat have the bypass poppett valve design, that lets air bypass the thermostat? That design can really help burp a system after a refill!!!

A bunch of thoughts for consideration, let us know how it goes.

 

This is the relay for the fan that I had bought......

http://www.ebay.com/itm/Dodge-Plymou...pHJSnQ&vxp=mtr

Well, I got one locally, but like this one. Perhaps the reason I can't find it on the car is because it's the black relay in the fuse box under the hood as you stated, Paw Paw. I'll check the water issue for an air pocket.

What gets me, is he drove it an hour one way, then almost an hour on the return trip before any issues started.

 

You may have more than one problem, so put Everything on your suspect list & require all suspects to pass their good test.
The description for the relay you purchased on the EBay link, says it's a Used part, so who knows where it is on the quality scale?

 

I have a written list of things to do. I am waiting on new parts to arrive, then I'll get busy. Hopefully the new parts will cure the problem so I can focus on what I WANT to do with the car, not things that NEED to be done.But, the needs outweigh the wants.

 

So, I posted a relay that I bought for this car, is that the wrong one, or, is there one like it on the car?

 

Have you performed the cooling fan relay test, in the first paragraph of post #2 & if so, did the fan turn on?

 

Heading out now to do that.

 

The fan was off on initial start up. I turned on the a/c, the fan came on. Relay would appear to be OK. I have the new temp sending unit in route. It may be faulty, causing the gauge to read incorrectly at times. Maybe that's why the car went one hour in one direction, then nearly that distance on the way back before the gauge showed hot. Once the gauge showed hot, it started going back down.

I am going to drain the water system and flush it out, then add new fluids (water, antifreeze and a bottle of water wetter), and see what happens. I will put the car on an incline as you stated.

 

Hold on, resist the urge to toss parts at the problem on a whelm. Trouble shoot, get a positive result, Then replace the suspect part that's tested bad.
Did all those cooling system items you've replaced check bad, or highly suspect, that caused you to replace them, or were you tossing parts at the problem & hoping for joy? Kinda sounds like you may have some spare parts if they're ok.

If the old coolant that was in there when you replaced the radiator & other parts was degraded, did you use a cleaner to descale the cooling system before adding new coolant then?

Is the coolant in there now in good condition, no rust, slime, floating debris? If it's dirty/rusty, use a good flush product to clean it out Before adding any more new cooling system parts.
No need for a "water wetter" to be added to a quality coolant. Just mix the uncut recipe with distilled water 50/50. You can catch your home AC condensate for distilled water, rather than letting it run down the drain.

On the temp sending unit good/bad question, locate it & wiggle it's electrical connection, to see if the gauge moves. Check it's electrical connector pins/sockets for corrosion, loose fit. Check it's ground to the engine block. Check it's resistance range with temperature, to see if it's in spec.
If you replace it Don't use any PTFE ribbon dope to seal it's threads, as that can cause a faulty ground connection to the block & cause more woes. Use a liquid thread sealant like Loctite PST 56507, or the like liquid thread sealant that can flow so to allow contact between the sender & block threads.

When the engine temp was showing overheat, did the engine smell hot"

The engine temp climbing to hot, then dropping down, sounds like a sticking thermostat. So, when you replaced the thermostat, did you use a quality one, or an inexpensive after market one?
Does the current thermostat have the poppet bypass valve feature? If not you'll need to run the engine until the thermostat opens, to burp any entrapped air behind it.

Let us know how it goes.