bigstrusk Posted July 22, 2022 Share Posted July 22, 2022 (edited) My brother was driving my car at an LRP HPDE event the other day. At the end of the 1st 20-min session pulling into the paddock, the temp light went on and coolant had blown out of I believe the top of the overflow. Coolant in there was boiling. Didn't overflow again (nor light) for the other sessions but could hear it reaching high pressure with whistling. After each session, the overflow was at or near the top. Certainly was pressure in the rad. No engine mods on the car. Water pump replaced 15k ago (with TB). Unsure if thermo and coolant were reused or not then. Coolant color is slightly dirty green. Admittedly, it WAS 90°+ that day and it was HPDE, so harsh conditions for sure. That being said, my bro was not pushing the car as hard as I would have been (thankfully I suppose). I'm wondering what to do about this, if anything. I DO plan to do more HPDE. Never had a cooling problem prior, though never ran the car that hard. What are your thoughts? Edited July 22, 2022 by bigstrusk Link to comment Share on other sites More sharing options...
DrD123 Posted July 23, 2022 Share Posted July 23, 2022 might want to check for combustion gasses in the coolant... a head gasket failure can give symptoms like that, as can a leak somewhere in the coolant system (if the cooling system can't hold pressure, the coolant can boil) a bad thermostat could cause problems, too. (I'd be pretty surprised if they re-used the coolant, but it wouldn't be surprising if they didn't replace the thermostat) 1 Link to comment Share on other sites More sharing options...
bigstrusk Posted July 23, 2022 Author Share Posted July 23, 2022 Thx for the reply, DrD123. I'll start with the pressure/cap. Below tester looks well-received and price is right. I'd like to check the fans as next step. Will have to think about how to jump em and test relays. I've been around Subarus long enough to be leery of HG, but I'd still be quite disappointed if that was it. 115k of strong maintenance and light usage ('til now). Mityvac MV4560 Automotive Radiator/Cooling System Pressure Test Kit, Contains Adapters to Test Most U.S. and Asian Cars, Light Trucks and European Vehicles https://a.co/d/ibHxvGA Link to comment Share on other sites More sharing options...
silverton Posted July 23, 2022 Share Posted July 23, 2022 (edited) If it's an '11, shouldn't you have blue coolant? It does sound like you have some sort of cooling system inefficiency going on. You can easily test the fans by turning the AC on. They should both run. I do gotta say, I was under a 2000 outback with 130k on it the other day and was absolutely shocked, the head gaskets were perfect with no evidence of work done. They were also in 500-1000 miles early on their 3k interval, so.... either you pay for oil, or you pay for head gaskets. Edited July 23, 2022 by silverton Link to comment Share on other sites More sharing options...
bigstrusk Posted July 23, 2022 Author Share Posted July 23, 2022 (edited) I was thinking about that too re: the coolant. A local shop did the job so I doubt they used OEM fluid and/or additive. If I don't find anything odd elsewhere I'll likely change that, maybe with some Water-Wetter -type enhancer. TY for the AC tip. I was also considering flashing the ECU w/ a lowered fan engagement threshold, but that'll be a last resort. 5 hours ago, silverton said: If it's an '11, shouldn't you have blue coolant? It does sound like you have some sort of cooling system inefficiency going on. You can easily test the fans by turning the AC on. They should both run. I do gotta say, I was under a 2000 outback with 130k on it the other day and was absolutely shocked, the head gaskets were perfect with no evidence of work done. They were also in 500-1000 miles early on their 3k interval, so.... either you pay for oil, or you pay for head gaskets. Edited July 23, 2022 by bigstrusk Link to comment Share on other sites More sharing options...
bigstrusk Posted September 1, 2022 Author Share Posted September 1, 2022 (edited) Checking back in. Still hasn't overheated since. Finally got around to testing stuff with the Mityvac. Cap holds up to and releases at 15psi. Static pressure is consistent at 18psi. Dynamic test showed no immediate jumps or pressure bouncing, stays consistent at 18psi. Factory specs are 14-18, with 12 being service limit. No signs of coolant in fluids. No seeps or leaks I've ever noticed. Fans both kick on with AC. Only thing I can think of is that it wasn't filled or burped properly when the water pump/TB was changed. The parts kit on the service invoice shows a thermostat as well. Is another flush and refill even worth it at this point? I have some SOA conditioner to throw in regardless. Should I just top off and monitor? So frustrating... Edited September 1, 2022 by bigstrusk Added OEM specs Link to comment Share on other sites More sharing options...
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