2005 M6 base 138,000 just started overheating last week. It is my daily driver.
topped off Dexcool, got it home, after cooling. Same thing next day after about 20 minutes of driving. Nothing under hood seemed out of ordinary. Radiator is new as of Christmas.

i just put on a new surge tank cap 2 days thinking that was it. I installed a new thermostat also then. I noticed the surge tank hose with the T that goes to water pump had a tiny crack at the T and was dripping. Do I ordered a new GM hose assembly and just installed today.

was running ok, adding coolant as I ran it, revved to 2500, heat on full. Walked away for about another 5 minutes and it said check coolant level and was steaming. This was just idling, I had not driven it yet.

attached video is the overheating with sound

 

Think I saw your post on FB just a bit ago.

do you hear the fan kick on and verify it’s working when it reaches temp?

if not, check the fan plug wiring and see if it’s cooked.

 

Start motor, make sure A/C in on and radiator fan should come on right away.
The HVAC system needs air moving through the condensor in front of the raditor when car is stopped, and so will kick fan on even with motor is not up to temp yet.

If fan does not come on, then check fan connector on side of radiator to make sure it not melted.
red dot it on the connector,


And when you have it apart, then check to make sure connector is not melted,


If upper connector is not melted, then need to check lower connector to PWM that may be melted down there instead.



If radiator fan does come on, but still getting the over heat message, and sure that the T stat is fine, then need to start the car, remove the reserve tank cap, and put a vacuum on the reserve tank, to burp any air out of the system. Hence if you have air in the system, then it can get trapped at the radator coolent temp sensor,


Makes the temp sensor freak out with wide temp sensor changes/swings, and causes the car car to throw the temp codes.

As for T fitting, go with after market brass one, instead of the oem plastic on that will just break again over time.

Last one, if the T state you installed did not have weep channel, or you did not get the weep channel TDC with installed in the pump housing, then may have to go back in. Also, if Fan comes on, have air purges the system, and T stat it good, may just be time to replace the water pump. The problem with the pumps as they get old, can have the shaft weld to the impeller break, and although the pulley is spinning via the belt, the internal impeller may not be spinning instead.

The last one that comes to mind, is one of the head gaskets is leaking, and could be causing the problem as well. hence its not always loosing fluid, but the other way around with cylinder shoving air into the cooling system isntead.

 

The fan did not kick on when i turned on the AC after staring the car, like was said it should. connectors look fine inside and out

 

It looks like maybe my surge tank may have a crack. I am having a hard time finding a replacement for one also..If anyone has any suggestions, or can help, that would b e great

 

If you're in TN, I'd look up Junior Samples at BR549. He's the CFO of "vettepartsinthesticks.com. I apologize. It's been a long week. Hope you boys will have a very memorable and safe weekend

 

SOLVED!! A rock was jammed way in the radiator fan, where I could
not see. Fan was not turning on with AC on. Tried moving it by hand, wouldn’t move. Rocked it back and forth, thinking maybe a stuck bearing or something.

A rock dropped out and fan spun freely, then with back on, ran fine. I let the car run with coolant level good, occasional rev to 2509, temp was great, about 110 or so.
2 test drives, one for about an hour, was about 108 and 114 sitting at stoplight. No problems at all.
A damn rock

 

start to make sure engine fuse box fuse is not burnt out for fan. also check the connectors at the side of the raditor, since it a always hot, and should have 12 volts across the large red and black wires, If good there, then check the pwm connector for the same power.


From there, Check the ground for the pwm to the chassic, then jump the radiator fan ground wire at the PWM connector still connected to pwn. to ground on the chassic (how the pwm controls the fan via the negitive side, with hot directly to the fan at all times) and if fan kicks on, then maybe burnt PWM.

https://www.corvetteforum.com/forums...g-diagram.html

If fan does not still come on with power to the fan and its ground directly to ground to bypass the pwn, then problem with radiator fan, and with car off, just reach in to see if it free spins by hand, or is bindy as hell from it brushes worn out,or bushing starting to seize up
Note, You can rebuild the raditor fan motor on the cheap, but may just be easier to just replace the entire fan assembly instead.


Short of that and PWM still good, then negative control wire off the ecm to pwn has problems, or aftermarket tune that screwed up the control voltage/temp setting in the tune instead.
So to check for that, again, start motor, turn on A/C, and the voltage from the ecm negative control wire(green) through multi-meter with negative probe on it, and other probe of the meter to 12V positive at the battery, should have the voltage at slightly over 5 volts. You can start with the connector on the side of the radator, but make sure to check it as well on the PWM connector too.

Again, when A/C is on, it will control the fan to turn on (increase the negative voltage on the Green wire to slightly over 5 volts on the digital meter to the pwm, for it to start to pulse the fan on.




Or fan stuck due to rock wedge in it, as you found out the case instead.

 

I have the plastic surge/fill tank for sale PM if needed. It is used.

 

One of those...
If I hadn´t seen it, I wouldn´t have believed it!