Overheating only while idling

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.

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?

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

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.

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.

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?

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.

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.

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.

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.

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.

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.

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.