240 is really pushing it. I am surprised the failsafe on your ems hasn't opened it up. They generally fail open.

 

Yeah, when my car was cold i would open up the cap and it would have pressure under it. Sometime it would let a little bit of coolant out. It seemed odd to me. After i replaced the headgasket i had tried this on a couple different occasions and driving it on several trips and after it was totally cooled down there was no pressure behind it with the new headgasket. I dont know if it was coincidence or not. Maybe someone with another known good headgasket can give that a shot on their car to see if they have pressure behind the cap. But like i said a few thousand miles after replacing the headgasket mine didnt have pressure.

 

From my experience with 2 other cars I have owned in the past and had thermostats fail, they failed closed and the car overheated. My moms Honda Accord did this back in 96 and she got it so hot that the head warped and had to be milled. I'm guessing that it's just a crap shoot if they fail closed or open unless you have one of those fail safe thermostats that always fail open.

 

Hmmmm......Thats making me wonder if it is the HG then. I mean, when it's cold it would relieve a little pressure and maybe a couple drops of coolant. I always figured that it meant the the whole system was very well sealed. Who knows.....

 

My IP headgasket overheated and blew at 220.
Totally my fault though but i had the aem ems and did not have the coolant mod fix so i had no idea i was overheating

 

I have my check engine light set to 220 degrees and when it came on is when we started watching the temps. We let it get up to 240 degrees to make sure it wasn't a fluke and was climbing. My tuner said 240 degrees isn't enough to blow the HG. I would assume that you were probably closer to 260 degrees when you blew your HG.

 

A leakdown test will very easily tell if the headgasket is blown.

 

^^ Mine did the same EXACT thing. I had some of the symptoms your talking about. My car would sit for 2 days, and i would take the cap off and it would have a TON of pressure behind it. Car would heat up, sometimes. Air was leaking out of the compression chamber and causing air bubbles, plus my car was eating coolant like its job. My HG was REALLY blown though, i was getting the WRX start up and all.

Good luck getting it fixed. I would just try the thermostat, its alot cheaper and easier than the HG, and should probably be replaced as maintance anyways.

 

I guess if the AEM logs were incorrect then it could have been higher.

 

Sounds like a thermosat.... Whatever you do..... Don't risk getting a thermostat other than OEM. Take it from me who has experience in this department.

Quick way to check if it's a bad headgasket is to look under the oil cap and look fore a milky look. Google it and you will probably find some pics of what that condensation is supposed to look like. If you have an air compressor, then yes, do a leak down and you'll confirm 100%.

Check your IC piping to make sure that they haven't come loose. I had the same thing happen.... I was running 24psi (on a GT35R) and then the pressure dropped to 19psi at 7200 rpms. Took the wheel off to check all the IC piping and sure enough, a joint came loose.