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#1: 03-09-2013, 08:46 PM
Another overheating problem...
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Car: 96 Legacy L Postal, 94 L Postal
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...with my 96 2.2.

In the past month I've changed the thermostat, radiator, radiator cap. The thermostat went out and I discovered the PO had somehow chipped the upper radiator hose connection. Ran fine after that.

A couple of weeks ago, about 2 hours into delivering mail, it overheated. I didn't really know why it was doing it, so I let it cool down, and followed the burping procedure while filling it- slowly. But, it kept overheating every 45 min or so. I checked that the fans were working, bled it again, and drove it for about 80 miles on the highway- no overheating. I figured everything's fine, right? Just an air bubble?

I drove it around town all week with no problems. But the next week when I did the mail again, in almost the exact same spot, it overheated again. I bled it and filled it, and it maintained correct temp., but the heater would only blow hot when I accelerated- when idling it would go cold. I bled it again a couple more times (every 45 min or so). The last time I bled it, it made it for the rest of the route (about 2 hours) without overheating, and I made it home fine.

Next day, in almost exactly the same spot, it overheated again. Same issues, heater only hot on acceleration, etc.

At this point I knew there was something really wrong, so I asked my mechanic and non-mechanic friends. Their ideas:

-Water pump fins corroded causing cavitation and air bubbles
-Heater core clogged
-just overheating from the hard conditions (it hasn't done this before and adding wetter water didn't change anything)
-Transmission getting too hot, trans fluid is actually heating coolant instead of being cooled.

I wasn't able to get it to overheat again, but on a quick trip to the store it heated up to operating temp and the heater was blowing cold at idle. On the way the heater worked, and when I stopped it continued to work, although it was noticeably hotter when revving the engine.

Frustrated and still thinking I didn't bleed it enough I took it to the dealership to have it flushed. Their contribution- bad headgaskets. "These cars had head gasket problems" -"The 2.5s did" -shrug-

After some observation I realize that the radiator is not pulling coolant back out from the reservoir. There are no noticeable leaks in the res. hose or anywhere else visible. Water pump isn't leaking as far as I can tell.

I'm not saying it isn't the headgaskets, but there are no other symptoms. Another theory I read about is that there is a minute crack in the block which, when the engine heats up enough, causes the system to lose pressure and thus the vacuum to draw coolant from the res.

Plus, I'm really hoping it's not that. I was hoping it was an air bubble to avoid doing the water pump or heater core
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