Need help replacing thermostat

[floridamba]

I'm troubleshooting a coolant leak that appears to be coming from the thermostat gasket. I've drained the cooling system, removed the top hose, and removed the left (facing the car) bolt. The right side bolt is really tight and the 8mm nut head on it is starting to strip. I've lubed it with WD-40 and let set overnight...

Any advice on this? I would rather not take off the big pulley assembly (power steering and alternator). I am a skilled former motorcycle mechanic but cannot get to the bolt to put an impact driver on it.

Thanks for your advice.

[floridamba]

Well I got the second bolt out.. it had some water scale on it. The thermostat housing/neck had some corrosion on the bottom half of the sealing area and this was letting the pressure blow through.

I will check with the dealer tomorrow to see what a replacement costs.