hatchsiturbo

so the other day I drove my ap2 04 turbo s2 on the freeway wanting to see how it would do on warmer weather ...outside temp was about 91degree around 530pm...and I notice my coolant gauge was steady until 2 mile down the freeway it started to climb went up to half way then extra 1 or 2 bar then stop...I had the aem hook up to the laptop while driving and aem showing 205 and it stayed like that for good 5 mile down the freeway...so I pull off the freeway and was sitting at a red light and the coolant gauge started to fall back down to factory spot and I check the aem and it showed 193...so now I don't want to rely on my factory coolant gauge cause when I saw it go past half way I was for sure the headgasket was going to go. so I am looking to buy a external coolant temp gauge and buy one of those radiator hose adapter. I want to say for the adapter hose and send unit best location would be close as possible to the factory ect on the intake manifold but was wondering anywhere on the top hose would be fine. the further it is away from the head would slightly be few degree lower..looking for your guys input