When sitting idle, after roughly 10min the temperature gauge raises to its highest and will eventually start to overflow coolant. BUT, if driven even immediately after this the temp starts to cool off right away. This only happens when idle, Ive never had any other overheating issue even with a 9 hour drive. Could this be a bad temperature sensor? Recommendations on what I should replace first. Thanks!

DOHC 98 Neon

 

check and see if the radiator fan comes on. also, make sure it is sucking the air through the radiator and not blowing at it...It will make a whistle noise if it was wired the wrong way.

 

could this have anything to do with a CEL "Rad Fan control relay circuit"?

 

yes it could. what year is your Neon? on the 95's the relay is in the fuse box under the hood. on 96.5+ (i believe) its under the battery on the frame rail.

Its a common problem among all years.

 

Its a 98. What is required to fix this? replace the relay?

 

replacing the relay fixes the problem 90% of the time. the other 10% is generally a wiring issue or a bad coolant temp sensor. but replace the relay first. its like $40 at Autozone.

When you put the plug into the new relay make sure the plug's seal (its inside of it kind of its rubber) isn't coming out of it. When I replaced mine the seal was coming off a little, didn't think much of it till i ran through a small puddle and there went my relay and some other parts. so just a little warning.

 

Thanks for the info, Ill try replacing it. This is under the battery on a 98 DOCH?

 

I dont own any DOHC's but they should be in the same spot. so it should be under the battery either bolted or screwed (I've seen both) onto the frame rail.

this is just a straight on shot but it should look like this.

 

Appreciate the help. Ill get it replaced tomorrow as long as I can find it in stock locally. Ill update the thread when I see if the code comes back after resetting. Hope I'm killing two birds with one stone and the idle overheat stops too.

 

I noticed today, that the rad fans dont come on at all even with AC/heat on. I want to replace the fuse first. Does anyone know which fuse is for the rad fan? From what I've read if the relay has gone bad the fans should still spin up with the AC/heat on but they dont auto turn on when these are not on. In my case they just dont turn on EVER. Thanks!