ok so here's the deal, i have only found one thread that comes close to diagnosis, but there was not enough consensus. I just happened to check the coolant reservoir after driving today, i did maybe three 5k rpm shifts, and thats about it, i dont even do that many in a month, however, i got home, checked the coolant reservoir, and there were a few air bubbles popping up in there, wtf? my fan comes on normally, my concern is my engine temp sensor inside the car, my needle stays just slightly below the middle of H and C. Does anyone elses stay around there or more towards the middle or slightly above cold? if my fans are coming on and my sensor is not going past the middle, should the air bubbles be a concern? any help is greatly appreciated!

 

probably nothing to be concerned about if the temp gauge isnt getting hot, then it should be fine. Bleed the system if you are are worried about it - I havent done it on a Z, but its easy on a 240sx....

 

on the z the temp needle points slightly towards the cold once it is at optimum operating temperature.

 

thanks for the replies, i have been messing with it for the last 3 hours now, i have concluded that my temp is normal based your replies and where my needle is, and also it only happens when my z is parked slighty downhill which is where i park across from my house, for the last few hours i have drove around and stopped on level ground and checked and no bubbles, park back in my normal spot(slightly downhill) and 3 or 4 bubbles appear, so it seems the way i park may be starving something, but i will just have it bleed soon, thanks for the replies, goodnight!(11pm here in TN)

 

Sounds fine, hope you didnt have nightmares about your car overheating!

 

ok so im back, took it out during lunch hour, pulled into a car wash and checked the resevoir, still bubbling, temp gage normal, fans work, i dont have clue, stealership says $85 to diagnose, im gonna try a new radiator cap today, if anyone has 5 mins, could you please take about 30secs to 1min to check your coolant resevoir to see if it does the same thing. also, when i remove the radiator cap and start the engine is the coolant suppose to start rising? a lot internet threads say its not so im beginning to wonder about head gasket problems now

 

ok, i think i solved the problem by simply replacing the radiator cap, drove aroundin 80 degree heat for about 30mins, checked no bubbles so far.....fingers crossed

 

https://my350z.com/forum/forced-induction/356151-coolant-purge-nightmare.html