After installing a brand new (not reman) engine from GM, turbo, new transmission from GM, radiator, new coolant and turbo oil hoses, pretty much everything except the radiator fan. The fan comes on but I don't know if it is running correctly. It runs hot while driving. I've checked to make sure there are no obstruction to air flow through the radiator. Even though the the new engine came with a thermostat we changed it out with another new one. (the one we took worked fine, wide open at 185° F). My mechanic friend and I are at a loss as to why it's running hot. I don't know how to check the coolant flow rate and volume. Any and all suggestions are appreciated.

 

Welcome to the site, I have to ask, which new thermostat? AC Delco 131-158 , 180 degree? And coolant? Dexcool 50/50 premix? Did you burp the coolant?

https://www.chevyhhr.net/forums/how-...-system-60614/

 

Bad thermostats typically cause the coolant to take too long to warm up. Extremely rare for a bad thermostat to cause overheating.

Did you take the plugs out of the new radiator? Where the hoses hook up, sometimes they come with plugs to keep foreign material out.

 

The engine is brand new from GM (the second to last one in GMs inventory for the entire country, I also got the last automatic tranny in GMs inventory in the country). We installed another new thermostat after I ran it for a few days close to home and the over heating didn't decrease. I tested the original thermostat after taking it out. It was wide open around 185° F. No plugs in the the new radiator.

 

What is "hot"? The fan should keep the temp below 220F. 190F-200F while cruising is normal.

 

It has gone up to 221° F and rising while cruising before I had to slow down from 70 MPH. Even to old worn out engine didn't get this hot when running well above 80 MPH.

 

Yes to all,,, new pressure cap ,new reservoir tank, Like I said in my post, "the only thing that wasn't replaced was the radiator fan" itruns but I don't know if it's turning up to the correct RPM.

 

You could change the fan assembly to confirm if it’s working correctly or not, better to be sure then fry the engine!

so, did you burp the coolant? I don’t see you answer to my questions

 

I won't be able to do anything with it until Wednesday. The shop is locked up today and Monday and Tuesday are all about doctors,,,, I'll let you know how it goes then.

 

Based on the answer in post #6, I would say it’s NOT a fan issue. Air flow at 70 mph is better than the electric fan can produce.
Sounds like a coolant circulation problem. Some part of the system is plugged up or the water pump isn’t working.