20v coolant problem

[Bravothreezero]

Hi,

I recently got a 20v blacktop installed with an sq-engineering kit for cooling. Every 5-10 minutes or so the coolant temperature rises till the meter can't go further and then suddenly drops back to normal in half a second. We've tried to bleed the radiator to let the pockets of air out, but it seemed this wasn't the problem. Now we are replacing the sensor ..somehow I think this won't solve it (the sensor was new and a part of the kit).

any ideas what else it could be? Still some air stuck somehow?

thanks

Edit: it's not related to revving it seems to happen completely at random