Overheating after Boosting

[SUPERIUM]

Just recently my car started overheating everytime after letting off boost. The stock temp gauge literally will spike up past red and then drop before i can pull over to shut her down. The only thing I can think of is air in the system or bad tstat but its too consistent to be air and the tstat is a month old oem one. The car also has a month old alumminum rad, new oem cap, stock clutch fan and shroud. Also was thinking it could be the temp sensor/electrical issue but Ive never had issues with it before. '
Any incite would be appreciated since its tough to diagnose it since it only occurs while driving under boost.
I guess I should do a compression and leak down test though I doubt its a bhg since the car still pulls hard as hell, no smoke from the exhaust and the previous owner had the head gasket replaced before.
Thanks, Mark

 

[oldsking]

how about you do what you mentioned, compression check and leak test. Might also want to consider upgrading from an OEM gauge to a good after market for a more precise measure

 

[SUPERIUM]

Bumping this. Since October I replaced the stock rad with a cx racing alum rad. as well as the upper rad. hose, 2 heater hoses (too hard to reach the 3rd on on the d/s), heater valve, oem rad. cap and oem stat. Since then everythings been running great with no issues whatsoever.....until last week. I take a friend for a ride. Automatically know somethings wrong as the cars slow as hell barely boosting. I hit fuel cut once and car starts overheating immediately and then drops back down to around 1/2. I pull codes and get code 34 (abnormal turbo pressure). I check leaks tighten everything and reset ecu. Everything seems fine the next day. Day later I go to run an errand and starts overheating again after boosting WTF!! Once I get to the place I look underneath and see a slight drip...ok so its just a leak. Head home stay out of boost until right before I get on my block and it doesnt overheat. Get home, look for the leak....nothing WTF!! make up your effin mind! Burp the coolant system and drive it and temp gauge stays arnd 1/2...WTF.
Today I go get a block leak tester from AZ and all signs point to no blown head gasket, ok cool but WTF!! Searching and feeling around for leaks I feel the tiniest wet spot underneath the coolant res hole by the top of the rad. No way it can be that easy of a fix. I pull the hose off, inspect it and looks fine then flex/bend it and what do ya know theres a pin size hole I discover. That thing was probably pissing out coolant like a lazer beam during and after boost.
So now I got to go back to AZ and get some new hose and probably have to burp the system again just to be sure. Hopefully that was the issue and easiest fix Ive ever had to do to this car. So for right now.....yippeee!, for later.....WTF!!
I will update thread if all works well or not.