OK, this one's kinda puzzling me. My car overheated tonight...badly. Stopped the car after about 20min of driving in heavy traffic, heard it boiling from iside the car. Guage read dead center, fans not running, overflow tank boiling ferociously, WTF?? I remember watching the guage come up to normal operating temp when I left work today, and afte the car sat it went back down, but it never went up past 1/2. Zero leaks, coolant is full. Checked te oil for "milkshake" and thankfully found none but my oil is blacker than I've ever seen it (mobil1). Anyone heard of a temp sender failing so it would only read up to a half? I thought it was usually a all or nothing sort of thing. In fact I just scanned the temp sensor section of my FSM for a guy at work whose car shows full hot and the fans come on as soon as you start the car.

I'll look into it further tomorrow in the daylight but who thinks I've hurt my motor? Im used to my old all cast-iron mopar smallblocks and Jeep 4.0's, the idea of overheating that aluminum head really worries me. Funniest part is we've had a record breaking heat wave this week (37 degrees celsius tuesday), but today was unseasonably cool maybe 20 degrees at the time of the incident.

 

what is the condition of your rad? znd do your rad fans work? have the connectors come loose?

 

The boiling sound is a dead giveaway that there is air getting into the system somehow. If there aren't any visible leaks, it's probably coming in through the radiator cap. The metal cap and plastic housing (aluminum in your case?) expand and contract at different rates. So as your car is cooling down, it's very possible for air to get sucked in through the rad cap instead of coolant getting sucked in from the reservoir. A new rad cap and making sure you get all the air out of the system almost always does the trick (if it doesn't, you probably have a leak you haven't been able to find yet...). I change my rad cap every other oil change, which I'm sure is overkill. But I haven't had the "boiling coolant syndrome" in well over 100k miles now, even with a pinhole leak.

The coolant temp gauge is a two-part deal. The part going to your instrument cluster is no better than the oil pressure light - idiot gauge, more or less. A scan tool would be able to read the signal being sent to the PCM.

Best of luck!

 

Update and additional info:
Checked everything out the next day and I can't find any leaks. Checked the temp sender according to FSM and it's within spec. According to an infared thermometer the fans are working perfectly (within 0.5 degrees off and on). Rad was new last year. I also suspected the filler cap and I'll replace it ASAP (holiday weekend). So far I've driven the car a bit (with IR thermometer close at hand and checking everytime I stop), with no repeat episodes. I'll let you guys know if I figure it out.

 

Man this sucks, I am having a similar problem with my 95 Neon. All the sudden this summer the car started overheating. The rad looks good, my fans are coming on and very efficient. Coolant is circulating. I already cleaned the cooling system and replaced the thermostat, still with the same problem. I noticed that it only does it with the A/C on. The boiling happens when the reservoir heats up. If you have a mixture of water and coolant mixed rather that just coolant in the reservoir, this will happen. I noticed after a long day of driving my car does it occasionally. It started when I removed my Air Intake box and went with a cold air, I guess it exposed it to the heat off of the manifold. I am also looking for answers.

 

Read through the whole post again. You have air in your system that is bleeding bck off into the reservoir when you shut off your engine. The rad cap is the culprit most of the time.

Best of luck!

 

I am having the same exact problem with my Plymouth, so your problem isn't just with the dodges, but I have noticed its a problem common to the DOHC as I have a 97 expresso.

What I have found is that it is a relay problem within the rad's wiring harness. If you look just infront of your front pass wheel just infront of the mudguard there is a small relay stuck to the wall with a plastic molly. The first time this unit was replaced it was due to the fans not turning off and draining the battery when the ignition was off. I had the dealership fix the problem and if you are under warrenty this falls under the same relay problem.

Fixing it the first time solved the problem, at least for 7 years - it just came back last week, this time the fans were only turning on when the AC was on due to the fact that the AC fan is actually the second fan you see on your rad.


Replacing it, once again, is said to fix the problem, but I just finished replacing it today, not only did it not fix the problem, but it made my electric sys. go all screwey - under 45 mph and the dash goes dead and the battery has defused and won't charge up (granted it is an older batt that should be replaced anyway). There are a couple more solutions to re-rout the left fans wiring to some open jumpers on the body. I will check it out tomorrow and see what happens (after I get a jump and go get a new battery, of course)

As for the AC not blowing cold - I don't know what to tell you. I think it has something to do with the release of some of the gas due to the fact that the fans just aren't coming on to cool everything down. My AC died right before the relay went when I was pushing it hard on the highway. I just got it recharged and haven't had a problem since - I freeze my butt off when its cranked, and because of the relay problem I have to wear a hoodie when I get into my car, even though its 90F outside.

Thats it for now, hope to let yo know how it goes tomorrow.

 

Oddly enough this has happend to me before.. I took it into the shop my self trying to figure it out and it was only the thermostat. But you never know. I woul change it just to be sure, Also my temp in the car also stayed at 1/2 never went to hot eaither. Was on my DOHC 97 ....

MAC

 

I just replaced the thermostat and the rad. cap in the car and the relay that I was talking about earlier and my overheating problem with the fans not turning on was fixed. As an added plus, the guages are all back to normal, at least most of them. The car is still overheating, but it isn't.

All the fans are opporational and the car is actually running on the cooler side as the fans don't always need to come on (unless I have the AC running and the compressor kicks in). What I did find is that there is SOMETHING, God only knows what, connected between the actual AC switch in the dash and the temp guage in the cluster.

The temp shoots up faster then any car would ever overheat, telling me that the car really isn't overheating, plus when I push it (in neutral, so there is no cool air flow) nothing bubbles over. At least there should be some simmering in the coolent resevoir if the car was truely overheating. I turned the AC off and shut the car off, when I turned the car back to the on position, without turning the ignition, the guage was at a normal level. When I shut it off again, and turned the car back to the on position with the air **** on (once again, not actually starting the car) the guage blasted up to H and the cars warning alarm went off.

There is something funny going on with the actuall AC switch and the wiring of the temp guage. Let me know if this same thing happens to you with the AC and maybe we can pool our brains to find out what this gremlin is.