I'm sharing my experience with a thermostat replacement in the hopes it may help you guys if you ever run across the same issue I faced.

My 2018 Z06 appeared to be running a little cooler than the thermostat setting. Not much of a bother, expect the tachometer would occasionally light up cautioning against rev's higher than 5,500.

I decided to install a new thermostat to see if perhaps mine was controlling a bit cooler than specification. I installed a new, OEM thermostat with no problems. There was very little coolant that leaked out during the process. I drove my car only a few blocks testing it out when it began overheating. My first assumption was the new thermostat was faulty and failing to open. When I got back home, the cooling fans were running wide open, but the air was cool (indicating the coolant in the radiator was not hot).

After studying the issue a bit, I decided to remove the bleed hose on the thermostat body to see if coolant would exit the body while the engine was running. To my surprise, no coolant sprayed out while the engine was running. I connected a vacuum device and it took a minute to begin getting coolant up into the body. I reconnected the hose, test drove the car and it operated perfectly.

Somehow, I believe my water pump became air locked and even driving the car a couple of miles did not force coolant up to the thermostat in order for it to sense heat and open. Once I vacuumed out the air, it has run fine.

I've never experienced that before and haven't seen anything similar reported in this forum. Hoping if you have a similar experience this will help you trouble
shoot and get it fixed.

Regards

 

Thanks for the info. I'm getting ready to do the same thing. I wonder if you had run it with the radiator cap off, it would have purged out the air. Maybe someone else will chime in.

 

This is very good information. I had no idea the cooling system has a potential air lock up once opened.

Thanks for posting. I'm sure your recommendation will save others a lot of frustration.

The things we learn on the forum…

 

thanks for sharing your info.
good choice going with the stock oem t-stat.

 

I am about ready to do the same. What kind of a vacuum device do I need ?

 

What was the thermostat you replaced? OEM?

I have the same issue but turns out I think I just dont drive my car hard enough to get it up to the temp it wants to be at if I'm not driving for very long.

 

The car should be at operating temperature in 5 to 10 minutes no matter how it's driven.

 

Never had an air lock / trapped issue because I always use a vacuum system to remove all the air when changing radiator fluid.
Learned the hard way when air got trapped in my 2005 Honda's head and warped the head and blew the head gasket.
Thus I and almost all good mechanics use a vacuum device for issue free fluid install.