Since installing the GTM (PWR) radiator a month or so ago I got a few observations...

Level in overflow doesn't seem to rise when engine is hot...only thing I notice is it always seems lower than the last time.

Twice I filled it up to the middle but both times it went back down to about 1/4 full within a few hundred miles or a few days worth of driving.

Do I have air in the system slowly bleeding out or maybe something worse?

 

The system is self bleeding, so likely just air. Get the spill proof funnel if you want to get it all out at once.

 

Or a slight leak...my overflow empties out every week and I re-fill it, it only leaks when being driven...I definitely have a leak somewhere around either the thermostat or other coolant piping around that area (and I can smell it too), but I haven't had a chance to fix it due to my supercharger bracket being in the way...

 

I did find a leak due to a loose overflow bung under the radiator cap and tightened it... but it wasn't leaking much and it still went down after that. I checked it this morning and the overflow was bone dry so I filled it up again.... hoping it's just air, I'll update the thread once I find out more.

 

if your overflow was bone dry then you're sucking air back into your coolant system. bleed that bish with the lisle spill-free funnel!