Too hot before T-stat opens
 

I've currently got an M-tuned coolant reroute installed, stock radiator and fans, stock motor, no turbo. As it warms up, particularly during highway cruising, such as on my morning commute, it gets entirely too hot for my comfort levels before the thermostat opens. It will creep up to 3/4 or so position for maybe a minute and then as soon as the thermostat opens it falls directly back to 11 o'clock and stays there no matter how I flog it. The weird thing is that the fans don't kick on in this time. It doesn't get nearly as hot while idling until reaching operating temp, at least it didn't while I was bleeding the coolant system. It didn't used to do this before my previous motor took a dump and the coolant reroute sat on a shelf for 3 months. Is it maybe just that my thermostat is sticking and needs to be replaced? I read about drilling a hole in the thermo to allow some flow through it all the time, is this now necessary? How big of a hole and where exactly does it go? Any other insight?

Thanks in advance

burp the system?
I had the same symptoms and later found out I had air in the system.
Never had a problem since.
Stock t-stat. DIY re-route exactly like BEGi's

T-stat in backwards?

I don't believe the T-stat is backwards. It was functioning properly before and I never pulled the remote housing apart. That being said, I can't be completely and totally positive it is correct.

I did burp the system, but maybe not well enough, it was getting dark by the time I called it quits. I'll give it another shot with one of those bucket things that attaches to the radiator filler. Is it likely that an air bubble works itself back to the back of the block around the sensor, heats up and then gets sucked through the system when the T-stat opens? Then when I crank it cold again the bubble works it's way back all over again?

Possibly. All I know is when my car supposedly "overheated" I cranked the heater on and it was blowing cold. Went out and touched the rad and it was barely warm. Car was nowhere near hot let alone overheating. Then 5 seconds later temps plummeted down and it was barely even warm
Must have been a bubble.

Quick and easy to check too, so that's what you should start with

This is a classic air-bubble symptom. Massage the hoses, jack the front of the car up, whatever else.

While it sounds like the main problem is an air bubble, if you have a remote(away from the motor in a hose) thermostat, you should drill a small hole in the thermostat flange to allow the warm water to get to it early. A hole 1/8" is sufficient to accomplish this.

I had the same problem, always withing the first five or ten minutes of driving. It went away after about ten or so cold start ups.

Sorry I couldnt be more help

I guess it's an air bubble then. I'll do some more burping after class today. The T-stat already has a small hole in it, came that way from M-tuned. Hopefully it's just a damn bubble and it goes away, overheating is not something I want to deal with.

my car does the same thing. aem reads temps up to 208-210deg before the t-stat opens then drops to 180. it's been doing this since the m-tuned reroute install 6 months ago. it doesn't show hot on the gauge just shows it on the aem.

air bubble... i bled the system and had a bubble about a half gallon in volume. I've still got a smaller one stuck in there somewhere too. It still over heats a little before the T-stat opens, but for much less time and much less hot. I need to pickup one of those spill free coolant funnel bleeder thingies to do it right.

At least the M-tuned kit I installed (from FM) already had a small hole in the T-stat housing, bypassing the T-stat. They refered to it as an "air hole" in the instructions, helping to air out the system and it should be mounted pointing up.

I've had the m-tuned kit installed since about mid-summer and the past couple weeks mine's been doing this as well.