I have a 2005 Buick Rendezvous that is overheating a few months back it started overheating so I removed the thermostat. This solved the issue for a few months than it started overheating when I would Idle. So, I took my car into the shop they advised me to repair my lower intake manifold gasket And my thermostat to fix the issue. I replaced both now it's overheating even worse before it would only overheating at idle. Now it's get hot even on the highway and it struggles to get the temperature down. I don't notice any massive leaks and no smoke coming from the exhaust. Please help from what I read could be fan, fan relay, or radiator. The car has 185,000 miles
If it were the fan or relay the problem of course would be most noticeable sitting at idle, not on the highway. It is also a very simple matter to verify visually whether the fan is coming on when the engine reaches operating temperature.
You could check the radiator for clogs. (After 20+ years it's certainly possible especially if the cooling system has not been properly maintained.) It's also possible you have a blown head gasket.
See the troubleshooting guide of the site FAQ for further details.
