My buddy's 2003 Corvette has been having problems overheating recently we've replaced water pump, thermostat, temperature sensor, and coolant reservoir, pep boys cleaned the radiator. Have bled the coolant multiple times temps still get near 240°. What solutions can anyone think of, what other parts could be bad to make it overheat.

 

Are the fans coming on?

Is the lower valance still in place. The chin below the bumper really needs to be there.

 

Yes fan are coming on and the lower valance is still in place

 

They cleaned the radiator? Was that just a blow out cleaning (exterior)? Maybe pull the lines and check flow through the radiator. Inside could be "gunked" up possibly and impeding flow.

 

The lower center valance can sometimes get bent from curbs or driveway angle and angle backwards. This happened to me at my old house and caused my temps to rise. Straightened out the angle to the same as the side valances and the problem was solved

 

You might to replace the radiator cap, I believe it should be 16 Psi, and I think your main problem is the radiator. My 2003 base sits at 200 degrees and only get about that to 205 even during the hottest months and sitting in traffic for hours. You might want to make sure nothing in area in front of the radiator and AC condenser is not fouled with trash, I have seen some with whole plastic bags sucked up into the space in front of the radiator, and even better is replace the radiator with a Dewitt's aluminum radiator, but you still need to make sure the front of the radiator is clean. Before I put my away for the season I blow out and check the space in front is clean and free of any trash.

 

Did you replace the tstat with the original 190? Try a 180. You indicate you cleaned the radiator. I was not aware Pep boys could clean out the inside of the radiator. maybe have the radiator boiled out to clean the tubes. Our radiator has plastic side tanks that are glued on. FYI, sometimes the side tanks can start to leak because of the glue failing. If you do replace the radiator, as stated above, go with a DeWitts. It is an aluminum racing radiator with aluminum side tanks that are welded on. And even if you had the radiator cleaned on the outside, at least we know there is nothing in between the radiator and the ac condenser. That's Good. Did you by chance add a front spoiler? Some of them have inlets on the left and right sides of the spoiler, that's bad. Others have the air inlet in the center of the spoiler, that's good, even necessary. Also consider as i Did, having the fans retuned to come on at lower temps. On an 03, the first fan comes on at 226, and the second fan comes on at 230.
I have set mine to fan 1 at 195 and fan 2 at 200. I installed a 180 tstat and installed a Dewitt Radiator and fan system. I never get above 200. Cruise around town at mid to high 180's.
Also, what water pump did you buy. My pump worked good but I decided to replace it anyway to be on the safe side. The motor ran 5 degrees warmer with the new pump. I bought a cheap Chinese knock off. As I understand it there are 3 levels of purchasing GM parts. The 3rd ( I think its called Gold ) and most expensive level is what came with your car, I believe. I ended up putting the original water pump back on and recovered my 5 degrees.

 

Pep boys may not be completely familiar with vette heating issues.

Jack up the front end so you can crawl under the radiator shroud to view the ac condenser fins and get a good look up in the corners. Just taking a brush to the fins can make a big difference.

Alternatively, unbolt the four screws holding down the top radiator and you can see down between the radiator and the ac condenser. There should be no debris, twigs, leaves, or dirt visible. If you don’t have access to compressed air, even a strong stream from a garden hose can help.

Another easy replacement is the thermostat. Use stock 187° or aftermarket 180°. The thermostat will not make the engine run cooler on its own, but if it’s stuck it can make the engine hotter.

I drive in mid-90’s humid weather with the ac on half the year with a stock radiator, and the engine temp hangs around 205-210°. Most of the time people are having trouble it’s the thermostat, clogged radiator and/or ac condenser fins, or the lower valance. Personally eliminate the fins first.

 

Under what conditions do you see 240 degrees? Highway speeds, slow city traffic, idle, all the time?

Can you post a photo of the front end showing the bumper and the 3 piece air dam.

When was the last time the temperatures were running a more typical 192 to 200 degrees and were any vehicle modifications done since then?

 

Just a thought, have you displayed the coolant temp on the DIC in addition to looking at the dash gauge?

 

Changing from a 195 degree thermostat to a 180 degree thermostat is not going to fix the problem at the base of your pals heating problem. These engines were designed to run at 200 degrees, most engine oils don't begin to work properly till the 195 degrees is met, and hitting it with a parts canon is not going to do much more than empty your back account. Stick with the basics A good clean radiator, next cooling system pressure 16 psi I believe, clean clear airflow from the front bottom, the front air-dam is very important. All C3 -C4 and C5 are all considered Bottom feeders, not my name for tem but, and the number of C3-C4 and C5 out there is confirmation that the "front under feed of cool air works and works well is used properly works fine" Bookyoh is spot on, you or your pal needs to document when and were the heat gets to above 210 degrees. I may be graded as my 03 never gets above 205 but is totally OEM.

 

Moved to C5 Tech.

 

“Nearly 240” isn’t really hot, depending on circumstance.
For the ‘03 the fans come on in low speed mode at 226f and high speed mode at 235f. Both fans always run at the same time.

 

187 is stock.

That does not solve the issues...it just adds another variable.

Second fan turns on at 235

So your thermostat opens when the coolant temperature is 7 degrees cooler, and you are forcing the engine to operate outside of the intended design. To what end? Other than seeing coolant temperatures on your gauge that you were programmed to perceive as being normal with the SBCs of 50 years ago, what changed for your car?

 

So you are getting a warning message on the DIC or the engine is puking coolant? Please define what you mean by "overheating".