Overheating only while idling

Tiny
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  • 2001 MITSUBISHI ECLIPSE
  • 2.4L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 207,000 MILES
Hello guys,

For a while now I've been noticing my engine temperature creeping above halfway up the thermostat gauge while idling. Today it actually got up to the red while idling at a drive thru for 15-20 minutes with the A/C going on a hot day (80 degrees but car was sitting in the sun first). The thing is, the radiator is basically new, it was replaced in August of last year. I also have seen no coolant leaks or white smoke, so I don't think it's the radiator or any hoses. Also, I turned the defroster onto hot and the highest blower setting, which did get the temperature to drop a bit, indicating that it's not the Engine Coolant Temperature sensor either. So I've reduced it down to mainly water pump or thermostat. I've heard the EGR valve can also cause overheating issues, but if it's clogged it generally produces black smoke out of the exhaust, which I don't have. Does it sound like water pump or thermostat or something else? FYI water pump is 4 years old, and the timing belt that I got in the same kit wore out faster than it should, just replaced it a couple months ago. So that also makes me think the water pump is on its way out.

Thanks,

Adam
Monday, June 22nd, 2020 AT 12:24 PM

54 Replies

Tiny
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Hi Adam,

Does the vehicle ever overheat when driving at highway speeds? If it only happens when at idle in traffic or not moving, chances are the cooling fans are not turning on. Have you checked if they work?

Let me know.

Joe
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Monday, June 22nd, 2020 AT 6:31 PM
Tiny
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Hi Joe,

At any consistent speed, the car stays at or below halfway up the temperature gauge, so not overheating

Both fans are working. I'm not 100% sure if they're turning on and off at the appropriate times though (possible failing fan relay maybe). When the A/C compressor is running, they both seem to run. How do I test to see if they're turning on and off at the correct moment? BTW this is a problem I've had off and on literally since I got the car used in 2005. I had the seller have his mechanic looked at it for me for this very reason, and he basically just said "that's just the fan having to kick on, etc". It may mean there are just idle cooling issues with this car in general. But today it actually got up into the red zone for a minute before I turned on the heat to vent the engine heat a bit. The A/C was on and I was idling at a drive thru maybe 15-20 minutes. The A/C wasn't blowing cold either, seemed to be picking up heat from somewhere.
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Monday, June 22nd, 2020 AT 7:09 PM
Tiny
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There really isn't any issues I'm aware of. The idea that it doesn't overheat when driving leads me to believe there is a problem with the fans turning on in time.

The cooling fan is designed to turn on at 230°F. The only way I could tell you to confirm it is with a live data scanner. Basically, you could watch the coolant temperature sensor's signal to the PCM as it warms up. Right around the 230 mark, it should turn the fan on. Actually, the fan module should allow the fan to run for up to 5 minutes after the key is off until the temperature drops below that 230 mark.

If the fan is working, what I would start with is simply replacing the thermostat and flushing the cooling system. Also, make sure there is no debris blocking any portion of the radiator.

Interestingly, the A/C was likely not working simply there wasn't enough air flow through the condenser which is in front of the radiator. Also, if the cooling fan wasn't running at that time, it will compound the issue because the condenser can't do its job.

Let me know if you are able to get your hands on a live data scanner.

Joe
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Monday, June 22nd, 2020 AT 10:27 PM
Tiny
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Joe, I do have an ELM327 Bluetooth scanner now. From looking at the Car Scanner app, ECT sensor is one I'm able to get live data from. So from a cold start, watch the ECT temperature and see if the fan comes on at 230 degrees? Should I run the A/C or not? Also I do have two fans, I believe one is called radiator fan and the other is the engine cooling fan. Should I expect them to both come on at 230 or do they have separate parameters?
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Monday, June 22nd, 2020 AT 10:33 PM
Tiny
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Hi,

Leave the A/C off. When you turn it on, one fan should always be turn on with it. That is the condenser fan. I want them to be off to see if they turn on automatically when they should.

Let me know what you find.

Joe
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Monday, June 22nd, 2020 AT 10:54 PM
Tiny
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Hi Joe,

I ran my test today. The car started up at 113 Fahrenheit according to ECT, and the IAT stayed consistently at 113 to 115 Fahrenheit (it is a 90 degree day). Turning on and off the A/C got both fans to turn on and off properly. I had to drive the car around in a lot of stop and go to get the temperature up, it would only stay at 203 Fahrenheit while idling at first. After my drive and bringing it home, I got it up to 217 Fahrenheit, at which point both fans kicked on simultaneously. It stayed consistently at 217 to 220 Fahrenheit while idling, whether with A/C on or off. I've attached a picture of what my dash temperature gauge shows when it's at this level. This means the gauge is showing as 2/3 to overheating before the fans kick on. Based on your information about fans kicking on at about 230 Fahrenheit though, nothing seems abnormal here.

Anyway, there are a couple possibilities here, since I was unable to get it into the red again. First is unlikely, but I had the windshield replaced last night. It's possible the guy cleared up some debris blocking the little plastic vents beneath the windshield, and improved airflow. Do those vents have much effect though? The second, and more likely probability is it's an intermittent issue, and a component is beginning to fail but hasn't fully failed yet. You seemed to think possibly the thermostat? Do water pumps only ever completely fail, not partially or intermittently fail? Anyway I think it's safe to say the ECT, IAT, fans, and fan relays are all working correctly. I'm going to have to keep an eye on it and see if I can reproduce the issue. I suppose I partially reproduced it, since I got my gauge above the halfway mark. But what's the temperature where it really and truly is dangerous to your engine? 240 to 250 Fahrenheit? Thanks again, and I'll update you when I have any new info to share.

Adam
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Wednesday, June 24th, 2020 AT 2:52 PM
Tiny
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Hi,

The vents in the cowl below the windshield are basically for air intake to the HVAC system. As far as a danger zone, you don't want it to go more than 230 if possible. If you exceed that point, it becomes a concern.

For the water pump, usually they will leak when there is a problem or you will hear a bearing noise coming from them. They can't just totally stop working simply because they are belt driven. If it was to lock up and stop, you would know.

This may sound crazy, but have you tried replacing the radiator cap? If it isn't holding pressure, this can happen.

Let me know.
Joe
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Wednesday, June 24th, 2020 AT 9:57 PM
Tiny
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Joe, I did actually replace the radiator cap as an attempt at a cheap fix a month or so ago. Thanks for your explanations. When we replaced the timing belt 2 months ago, the water pump wasn't yet leaking from what we saw, so we didn't change it out.

This experience has me wishing for features on future cars. Ability to leave the fans on at all times in hot weather. And the ability to vent heat right out of the engine when it's too hot, like what turning on the heater blower achieves, except without heating up the whole car. It seems like the fans just wait a bit long to kick on. Although when I went into the red zone the other day, the A/C was on, and so the fans were too.

I know this is a worst case scenario, but what are the symptoms of a leaking head gasket? I'm paranoid about that being an issue ever since one less than trustworthy mechanic tried to say it was leaking. He claimed to have chemically tested the coolant to see if it was contaminated by oil, and said that the test indicated that it was indeed contaminated. Of course, he was saying all this to avoid replacing my radiator under warranty. We had to take pictures of the leak in order to get him to honor it. So I've replaced the radiator in September 2016 and August 2019, and sometime between 2012-2014. So I've consistently been having similar issues with the engine cooling system. When it all exploded on me in September 2016, I was in stop and go traffic on a fairly hot day. It was similar to now where it was fine so long as I was moving. So anytime I see the gauge go above halfway, it has me worried about blowing up another radiator. I almost am considering trying an aftermarket fan or something to add, something that's just wired to be always on. Just a thought.
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Wednesday, June 24th, 2020 AT 10:08 PM
Tiny
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Joe I did actually replace the radiator cap as an attempt at a cheap fix a month or so ago. Thanks for your explanations. When we replaced the timing belt 2 months ago, the water pump wasn't yet leaking from what we saw, so we didn't change it out.

This experience has me wishing for features on future cars. Ability to leave the fans on at all times in hot weather. And the ability to vent heat right out of the engine when it's too hot, like what turning on the heater blower achieves, except without heating up the whole car. It seems like the fans just wait a bit long to kick on. Although when I went into the red zone the other day, the A/C was on, and so the fans were too.

I know this is a worst case scenario, but what are the symptoms of a leaking head gasket? I'm paranoid about that being an issue ever since one less than trustworthy mechanic tried to say it was leaking. He claimed to have chemically tested the coolant to see if it was contaminated by oil, and said that the test indicated that it was indeed contaminated. Of course, he was saying all this to avoid replacing my radiator under warranty. We had to take pictures of the leak in order to get him to honor it. So I've replaced the radiator in September 2016 and August 2019, and sometime between 2012-2014. So I've consistently been having similar issues with the engine cooling system.
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Wednesday, June 24th, 2020 AT 10:08 PM
Tiny
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Interestingly, most chemical tests look for exhaust gases (carbon monoxide) in the coolant. You can see oil. LOL Have you ever noticed bubbles in the coolant after the vehicle was driven? Take a look through this link and see if you can do some of the checks.

https://www.2carpros.com/articles/head-gasket-blown-test

Joe
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Wednesday, June 24th, 2020 AT 10:40 PM
Tiny
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Lol. Okay that's probably just me misremembering what he said. Thanks for the link, I will try these tests out in the next couple days. I suppose the next part change I'll try is the thermostat as I've already got one. I've got a water pump too but I know that's way more of a hassle. I know there are some radiator additives too, head gasket sealers and some that supposedly increase the cooling power of the coolant or something. I think I know your stance on such products, but are any of those worth trying to see if I get a boost in engine cooling ability?
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Wednesday, June 24th, 2020 AT 10:46 PM
Tiny
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I checked the coolant about 40 minutes after driving today. I did not see any bubbles in the reserve tank. The coolant level of the reserve tank is sitting halfway between low and high. However, the radiator itself appeared bone dry. I still do not really understand whether I should be seeing coolant in there or not when it's not running. Because pretty much as long as I've been checking my radiator, it almost always has been empty when I checked it.
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Thursday, June 25th, 2020 AT 6:42 PM
Tiny
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The radiator shouldn't be empty ever. The reservoir should only be a stopping location for coolant that expands into it and then is drawn back into the radiator when the engine cools.

Do me a favor. With the engine cold, fill the radiator. Start the engine and allow it to warm up. Let me know if the coolant continues to stay full or starts to drop. Also, do this with the heater on high and if you notice it dropping, add a little at a time to keep it full. When the engine reaches operating temp and the radiator stays full, then install the radiator cap and turn off the engine.

Note that when the thermostat opens, you should see some circulation in the radiator.

Let me know what you find.

Joe.
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Thursday, June 25th, 2020 AT 9:10 PM
Tiny
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Low on coolant would explain overheating issues. Though I haven't noticed a coolant leak since I got the radiator replaced. Which would add credence to the head gasket leaking. I haven't noticed the oil being discolored, I'll have to check it tomorrow. I think I'm also gonna add some K Seal head gasket sealer. It has better reviews than the Blue Devil stuff, and it's 8 ounces you just pour in directly.
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Thursday, June 25th, 2020 AT 9:16 PM
Tiny
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Hi,

Before you add the sealant, make sure that is the problem. Honestly, I have seen such products cause other issues. Try what I said. Once we know that the radiator is full, then we can check it again after you drive it and it cools off.

Note, if you are losing that much coolant, it shouldn't be hard to determine where it's going. Either the oil will be over full with indications of coolant mixing or you will see a lot of white steam coming from the exhaust.

Let me know.

Joe
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Thursday, June 25th, 2020 AT 9:40 PM
Tiny
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Sure, I'll wait on the sealer.

So just to be clear, you want me to fill the radiator to the bottom of the neck of the radiator. Leave the cap off, run the engine with the heater on high, check to see if the fluid level goes down in the radiator. Then if it does, add a little more coolant. So it's safe to run the engine with the radiator cap off? It seems like it wouldn't pressurize correctly with the cap off.
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Thursday, June 25th, 2020 AT 10:58 PM
Tiny
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Coolant sprayed out all over the place when I ran the car with the radiator cap off. So I've filled it back up, put the cap back on, am running the car with heat on full blast for 30 minutes, letting it cool down, then checking it again. I also found a coolant pressure tester in the closet so I'll check the pressure too once it's cool.
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Friday, June 26th, 2020 AT 9:54 AM
Tiny
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The coolant is/was definitely the problem. It's staying a lot cooler now and the fans are kicking on with the temp gauge reading below halfway. Having the coolant be low was screwing with the ECT reading probably. However, I was seeing some white smoke/steam coming out of the back of the radiator, see attached video. That said, I had spilled a lot of coolant all over the place, but at this point it had been about 30 minutes of running straight and I think all that had already burned off. What does it mean when the white steam is coming out of the grating on the back of the radiator?

Edit: I didn't see any leaks, just the white steam/smoke. I'm going to let it cool completely down for 2 to 3 hours then check the level and pressure, top up, and run it again to see if the smoke happens again.
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Friday, June 26th, 2020 AT 10:30 AM
Tiny
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Alright after letting it completely cool off, I checked the coolant in the radiator again. And the top of the radiator was totally empty again. I topped it off with 5 or 6 ounces of coolant, ran it again with the heater on full blast, and after 10 or so minutes, the white smoke started again. I'm attaching a new video of the smoke. The pressure tester was hard to get working right, but seemed to be within the higher side of the range, 260 to 265 boiling over point.
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Friday, June 26th, 2020 AT 1:21 PM
Tiny
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I checked the coolant level again. 30 minutes wasn't enough time for it to cool off apparently, and it was still very pressured and sprayed out as I opened it and was very hot. I used a rag though so it didn't scald me. It was over full at this point, the coolant went all the way up to the cap. But I guess since it was still pressurized, that's probably not a useful test. I'll have to check it again when it's fully cool.

I will say that the reservoir doesn't seem to budge at all. Just seems to always stay right in the middle of low and high, whether running or not.
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Friday, June 26th, 2020 AT 1:49 PM

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