Strange Overheating Pattern
 

Hello everyone

I have a 2002 S40 1.9T

Recently, the car has been having some trouble with temperature control. I live in Los Angeles, so the weather is mostly arid.

The big thing that I started noticing was the fan staying on after engine is turned off. When I first bought the car a few years back, this happened only once or twice a month. But now its completely inverted, and it will only completely shut down once or twice a month. Any time I drive, when the engine is turned off, the fan stays on a few extra minutes.

Most of the time, there is no indication that the engine is overheating. However sometimes the temperature nearly hits the red line. It comes out of nowhere, I haven't been able to track down a common denominator.

The air conditioner is not on, the ambient temperature is in the 60s. I know for sure this has nothing to do with it because sometimes, I drive in 90 degree weather, and blast the A/C and it won't flinch.

Any ideas about what could be causing this? I have absolutely nothing to base a guess off of. There is absolutely no pattern involved here, its completely arbitrary when it overheats and when it doesn't.


Another thing that might be a clue is a problem with my turn signals. They seem to decide when they want to work. Sometimes it just does the quick flash (usually means the lightbulb is out) and the front turn signals dont flash (but are on), but a few days later its completely fine and all the blinkers work.

It happens to both left and right side signals, but they alternate. Sometimes the left doesnt work, sometimes the right, sometimes both. As with the overheat problem, there's no pattern.

This vehicle has a range of electrical issues. From the moment I drove it off the lot, lights didn't work normally, you had to jiggle them around to get the contacts to connect. I don't know if this has anything to do with the cooling system of the vehicle. The fans do work while the engine is running. They're pretty loud, I can tell that the fan is on most of the time. I have checked the front of the radiator and grille for leaves and such, but there is nothing. The airway is completely free.

and best of all, no check engine codes either.


I am desperate, please if you have any info, let me know

o-heating
 

I would change the thermostat...cheap and often the problem with overheating....

You have my sympathies. Intermittent electrical issues suck. I do have some questions to maybe help.

When the temp is near the red is the fan on? I would want to determine if the fan is the problem or simply doing it's job.

When the A/C is on does this same near overheating occur? Have you tried turning on the A/C when the near overheating occurs? I ask because you actually have 2 fans. One for just cooling and one that only works when the A/C is on.

Does the overheating occur at speed or when in stop-and-go traffic or at red lights? Again trying to determine if the fan is the problem. Normally the fan does not come on above 55 mph because air through the radiator is much faster than the fan.

Do you have an infrared thermometer? With this low cost tool you can test the actual temp of the t-stat housing to see if the car is truly overheating or if the coolant temp sensor is not accurate. Coolant temps should run around 190*ish. If they are up into the 230*+ range it's too hot.

Any check engine lights? Normally a bad t-stat will cause a check engine light.

Change the thermostat and temp sensor to start.

Strange Overheating Pattern
 

Well I hope you solve your problem. if not follow the instructions from Hudini in post # 3.
Must of the time is the module attach to the fan. is the connectors are good then you most replace the fan. it include the module.

Usually when the fan runs after the car is off it is either because the motor is hotter than 216° or the ECT (temp sensor) is old and bad.

Sometimes you can plug in a OBD2 tool and read live data. A rapidly erratic temp change will indicate a bad sensor as well.

High motor temps can also indicate a bad water pump. Do all you can to avoid an overheat.

Thanks for the replys everyone

Here are some answers to your questions:
"When the temp is near the red is the fan on? I would want to determine if the fan is the problem or simply doing it's job."

Yeah it is, the fan is pretty loud, and I can almost always hear it on. The time when the temperature gets high, the secondary fan (VERY loud) kicks in. A couple of times I only noticed the problem after hearing the secondary fan kick in.

When the A/C is on does this same near overheating occur?

Yeah, the problem happens regardless of the A/C being on or off. It has happened in both cases. If it makes a difference, the A/C cools just fine.

Does the overheating occur at speed or when in stop-and-go traffic or at red lights?

I dont typically drive highways or anything > 40mph because my driving is very local, but it HAS overheated once on a highway. Fortunately I had time to pull over, but this was a year ago or so, I don't know if it was a one time thing, or linked with my current problem.

I don't have a temperature sensor unfortunately

And no CEL codes either.

Back in November I had to drop my mom off at the airport, about 20 mi from our home, and on the way there, it was smooth sailing, but on the way back, I wanted to beat traffic, so I was a little bit more aggressive with the throttle (believe me, I am a very calm driver, by aggressive I mean normal) and one point, something happened (misfire maybe?) and the engine coughed and threw a CEL at me. It works fine now as if nothing happened, but the CEL is gone too, so I dont know if this has anything to do with this problem :/

First check the fluid level in the cooling system reservoir. I've seen strange behavior when the fluid gets low.

If the coolant level is good my next step would be to check whether the engine is actually overheating or if it's a faulty coolant temp sensor. This is the device I referred to earlier: Non-Contact Infrared Thermometer with Laser Targeting Cheap and effective to determine actual temps as opposed to parts changing. Now parts changing works, eventually, if you have the money. I've done it way too many times.

Hey everybody, I did as you suggested and topped off the water in the coolant reservoir, and surprisingly (or not surprisingly) it seems to have worked!

I drove in 85 degree weather with the A/C on full blast, the temp gauge didn't flinch and when I stopped the engine, the fan did not stay on as it did before.

I haven't had much experience yet to be 100% sure but it looks promising thus far

Thank you!

Keep an eye on it. Mine had melted the little hose on the back of the engine connecting the turbo's water coolant pipes to the head. The water was dripping down onto the cat convertor and evaporating so none was reaching the ground. You could smell the coolant though when you lifted the hood. If it gets low again it's time to break out the search light.