havoc

So, I've been driving it for 5 days now and I think the issue has been resolved. I do not believe I added enough coolant to the system. Apparently, when filling the coolant it is necessary to fill it to the very top of the filler neck. So, what I did was open the air plug (top screw on the passenger side of the radiator) and added coolant to the very top of the radiator fill neck. Then filled coolant to the "full" line of the overflow tank. Then ran the engine, revving it to 3000 RPM for 5 minutes until fan engaged. While doing this ran the heat at max with blower on 1. Then let the engine cool back to normal levels. Opened the rad cap and overflow tank and checked the levels. Both were at normal. Drove it at least 100 mi in the 5 days. City, highway, suburban, steep incline, fully loaded, pretty much every instance of driving. No overheating. So, hoping it's been resolved. Moral of the story: make sure your coolant is at full capacity when filling and make sure you have the air plug open when doing so. Any bit of air seems to cause weird issues which are difficult to diagnose.

OK, did a little work on this. Removed air vent plug, filled rad to very top of fill neck, filled overflow to "full line" Ran engine for 10 minutes idle, heat at high and blower fan on lowest setting, no overheat. Heat blew HOT, as in so hot you couldn't keep your hands in front of the heater. Thinking that there was air still trapped in the system after replacing the thermostat. When refilling the coolant I did not run the heat, which I now believe caused air to build up in the heater core since no coolant was running through it. I do not believe that there is something wrong with the rad. Top and bottom hoses were both HOT when the temp got within normal operating limits. Felt rad and no cool spots, so there I do not believe there are any clogs.

Overheating generally occurs when driving for extended periods of time. Hills also tend to be an issue. With the fans, is it normal for one to engage and the other not to sometimes? It seems odd that both do not turn on at the same time. Wondering if I should check my fan relay?

'97 Subaru Legacy GT 2.5 Has weird overheating issues. Very sporadic. Can be fine for weeks, then start heating 15 minutes after driving. Crank heat to HOT on full blast and only warmish air. When at normal operating temperature sometimes only one radiator cooling fan engages, sometimes both. There is a huge debate on whether a clogged heater core can cause these overheating issues or not. Some say yes, others say the core is not in the normal operating loop and will have no effect on the temp. Had the timing belt, water pump, and the head gaskets replaced. Still ran hot. Replaced the thermostat. STILL some overheating issues, but behaves slightly better. Tried burping the system by removing air vent plug, filling overflow to full line, and filling rad to the neck then running the car at 3000 RPM for 10 minutes. At this point, I'm stumped. Ready to tear out the ECT, radiator, and cooling fans and replace everything. Any thoughts?