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Overheat on idle

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So I had my first overheating today, and I am trying to figure out where the problem is. I have an idea of the cause, but thought that I could bounce the info off some others, to see what you all think.


My baby is an 05 LGT with 162k miles (260k km). I have a cattless up and a cattless shorty down pipe, heat tape wrapped. Timing belt (and all connected goodies) have been replaced once, so I am about due for a second. Recently replaced pass. side valve cover gasket, due to a leak. Recently bullet proofed TMIC while trying to diagnose a fume issue (which turned out to be the VCG leak). Just switched over to synthetic, and am about to do the first change. Lastly, I recently performed a full coolant flush (drained, drained engine core, flushed until clean). I did the coolant flush because I noticed that my coolant had some sludge in it, not milkshake like, and sludge did not appear to be oil. HG was a suspect there, but I also realized that up until now I have been following the subaru guideline for a coolant change, Which meant that all my coolant changes so far, have involved draining from the rad plug, refilling and adding the subaru additive. That means that only about half of the coolant/additive mixture was ever actually removed each time. Following their guidelines, and that means that I was increasing the ratio of additive, every time! After talking with my local subaru shop, I found that they don't actually put the additive in for the majority of the cars they work on. So I flushed the whole thing, to wash any possible sludge out, and started fresh, with only the subaru pre-mixed coolant. That way I could see if anything showed up, and rule out the build up of additive.


So far, about 6k miles (10k km) and nothing has shown up in my coolant. It looks as clean as I put it in.


This morning (also happens to be the hottest day we've had so far, 110F with humidity), I park at my home depot, and since i had a few minutes to spare, I just sat back for a rest. After about 10 minutes, I noticed that the A/C wasn't really blowing cold air, and the fan speed was increasing every few moments. Once it reached full, and still no cold air, I knew that something was wrong, looked up, and saw that my engine temp was just reaching the red. Shut everything off and checked under the hood. The overflow tank was full to the top, and steamy! I let the car cool, checked for any kind of leak, and went on my way (carefully). No overheating at all, since that. Temp gauge remained at normal for the rest of my driving.


Initially, after reading, I was again worrying about a HG replacement, but then I started to think and I'm not sure that would also cause the A/C not to blow cold air. I don't know the exact technicals of how the systems work exactly, but I beleive that the A/C condenser requires ~800 rpm in order to operate, which is leading me to think that the issue could be in the belt area. The belt itself, or one of the pullies/connecting components.



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Did you replace the water pump at 105K with the Timing belt? AC tends not to blow all that cold on a very hot day with low idle RPM's you would need to be moving at higher rpm for that to work effectively. It may just have been a similar effect on the car sitting idle too, you're not moving enough air over the radiator when standing still on a very hot day with the car running/AC on. If it didn't overheat when driving it may just have been that. Won't hurt to check the drive belts but even so... 110oF/humid and 800rpm won't blow cold air.
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^ this ?


Also its 10 y/o have you replaced the radiator caps ? what do the seals look like. I did mine last year because they looked less then perfect.



When you were parked with a A/C on, was there a car in front of you or were you in a open space?

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I did a little more investigating last night, and actually looked into most of the above questions before reading them. With the exception of the radiator caps......interesting point. I will have to pull them, when it cools, and see what they look like.


So, to answer the other questions:


I looked back in my records, and I had my timing belt replaced with the Gates kit, which does include the water pump, at 80K miles. So I shouldn't actually be due for another just yet, and upon closer inspection, the belts currently look fine and the tension seems about right.


Both fans run, but I did notice that when the car is off, they don't really spin well freely. I'm not sure what is normal for them, but I gave them a hand spin to see if there was any resistance or grinding, which there wasn't, but they didn't just continue spining (like a normal fan would) and slowly come to a stop. They just went about 1/8th a revolution, and stopped.


When I was parked, it was fairly early, so no other cars around. Open parking lot all around.


I also was looking at my tach, and if it is any bit accurate, then there is no way that it is idling at 800. Looks more like 700. I am running a Cobb map (and have been running the same map for the past 120K miles with no issues with it yet), and I have successfully used the Accessport cable to data log with my laptop. So I intend on hooking it up again, to see what is happening real time, including the idle RPM.


Lastly, and its interesting that this was asked, as this is something I noticed too, and think it's a key clue...I let the engine cool as long as I could, but it was still warm to the touch, when I checked it. Would not burn you by any means, but warm none the less. At that time, the coolant DID NOT draw back from the overflow. So I pulled the caps to see what the levels in the rad and resevoir were like, and when I pulled it, I could hear the pressure change, but missed my opportunity to feel if it was pos. pressure or in vacuum. (I did burb correctly when I did the flush)


Now, the other things I did notice as well, is that there has been coolant seepage from both the top and bottom hose connections at the engine (at the water pump and the thermo). I also noticed that the small hoses for the overflow, especially the section that sits in the overflow tank, are deteriorating.


I will for sure be replacing the overflow hoses, and the main hoses (I will be re-tightening the clamps while I wait for better ones to come in). I'll likely replace the caps as well, just to be on the safe side.


I also noticed what almost looks like some oil leakage from and on the waterpump. Is there a seal or gasket there, that may need replacing? or could the water pump be done (how would I find that out)?

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The fans are run by an electromagnetic motor, so they do not spin freely because even though there is no electricity flowing because there are still magnets at work.


The oil pump has the front main seal on it but the water pump is directly to the right on the oil pump. It is unlikely that the oil is defying gravity and traveling horizontally. The only seal near the water pump is your driver side head gasket. I am not saying that's what it is.


Double check your fan fuses. Make sure, with the AC on, BOTH fans are spinning at warm idle. If those are good, replace your thermostat (only like $30 for an OEM one). Then if you feel like it, do a compression check to see if any cylinders are lower which can indicate the compression leaking into the coolant passages.



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