I have a 1991 camaro rs 305 tbi 1 note to make Is I live in west Texas so weather is average 100 degrees but my car is constantly reaching 240 or so on temp couple times boiling point. I've changed the radiator, hoses, water pump, thermostat and have even flushed the system 4 different times with flush fluid. The air damn is intact and the car runs good no smoke no water in oil so dont think head gasket but I can not figure out why my temp is averaging 240 after about 20 minutes of highway driving. I do not think my gauge is wrong because once it goes over 240 i can hear it boiling in the radiator. If I come to a stop sometimes it'll start cooling down not eveytime. I originally had a 195 degree thermostat and changed it but all they had was a 160 so said screw it put that in on the chance it would help, they have been tested and they both open. Any ideas or help would be greatly appreciated. I do have an electric fan and it is functioning. But if I drive at night when weather is not as hot it really doesn't overheat mainly when it's 90 degrees or higher outside.

 

Remove the 160 thermostat and install a 195, use an infrared thermometer on the water neck to verify your temps. Check the condenser for obstruction, also check that your lower rad hose has a coiled wire to prevent cavitation.

 

Bottom hose does have coiled wire and I just changed thermostat last night, before hand it was going over 240 with a temp gun on water neck it's like it doesn't want to over heat just struggles but after being on the highway doing about 75 it'll take about 30 minutes before it finally starts getting warmer then I like to see

 

If you haven't, change the radiator cap. Systems need to stay under pressure to prevent boiling. The boiling point of water at 15 psi is 250F. Good caps hold 15 psi in the system.

If you get boiling, you have gases in the fluid. This prevents proper fluid flow. It increases the likelihood of cavitation at the pump... And pump flow drops off severely. Gases also prevent proper heat transfer in the radiator.

In short, boiling causes the whole system performance to drop off.... A lot... And the car overheats. Boiling is a big no-no.

 

^^^ This ^^^

240° is NOT "overheating". In fact the electric fan switch that came in lots of these cars DOESN'T EVEN TURN THE FAN ON until it reaches about 235°... IOW, 235° is the NORMAL temp at which the engine JUST BEGINS to "require" cooling, according to how it was designed.

And before you start up about "yeah but the boiling point of water is 212°", go back and re-read your high school physics textbook. While that little truism is of course true, it leaves out 2 major points: the boiling point of PURE water AT SEA LEVEL PRESSURE is 212°. Everybody seems to conveniently leave out the parts in bold when talking about cooling systems. In reality, the boiling point of a MIXTURE of 70% DISTILLED (not tap) water and 30% yerbasic green AF, AT 16 PSI (radiator cap pressure), is nearer 265 - 270°.

So yeah, put the right (195° ish) thermostat back in it, replace the rad cap, and make sure you have a mix of between 50/50 and 70/30 AF & water. Maybe even add a bottle of "Water Wetter" which aids in heat conductivity between the castings and the coolant. Then forget about "what I'd like to see" and instead concentrate on how the car was designed to work.

 

What type of fan do you have on it?


Is it the stock single fan? Could be the motor is worn / not pulling enough CFM or if you replaced it with an aftermarket, it could be inadequate.