My 2007 buick rendezvous started overheating but only boiling from resivor so the shop told me thermostat and flush was needed paid close to 400 to get that done. Right after i picked it up from shop about 30 miles later the temp gauge went up and so i pulled over once outside the vehicle i could see a huge puddle of all the coolant that had came out. I took it to.a few shops but could never get a honest answer or a straight one. This was a sudden occurrence not something that i delt with overtime so scared i parked it and havent started or moved since. Obviously the shop got me on the thermostat and flush being it broke down 30 miles after leaving the shop. I had my mechanic friend tell me she saw no coolant in my oil and i also do oil change regularly and they never mentioned discoloration either. I have had 0 smoke from under hood or exhaust and it seems to only boil out of resivor that was also replaced. I am tired of throwing money away or dealing with shops that want to tell you its bigger job than it is so they can benifit. Can i do anything to check myself? Average cost of pressure test? I am hoping its a manifold intake and not head gasket as last time i drove it right after new thermostat it over heated out the resivor loosing all liquid. Also wanted to add that this started in the winter when i would turn heat on...it blew 0 hot or warm air that was the issue that led to take it in...the heat was not coming out and this car has always had air and heat. Prior owner put radiator in it too.

 

I have no experience working on a 2007 Buick, especially not knowing which engine your car has, but I'm simply curious as to how you wound up on this website?