Model: C6 (convert, stick shift)
Year: '07 (LS2 motor)

After a cold start and while idling, the temp stays at 90C- 94C (194F- 201F) even if I let it idle for say 20 mins, the temp stays constant. But once I pull it out of the drive way and a few minutes in driving around the block. The temp both at the gauge and the DIC continues to rise and the coolant starts flowing out due to high boiling pressure from underneath the reservoir cap through the tiny hole

what could be a possible issue? the Fan fuse? I did replace the fuse but can't make sure if the fan is running or not, how could you make sure the cooling fan is running. Will turning on the A/C triggers the fan?

Maybe a bad temp sensor? sometimes while over heating the temp gauge starts fluctuating just right before the 'Engine Hot A/c shutting down' message pops up in the DIC.

An air pocket or vacuum in the block/cooling system and how to bleed if thats the case?

A blown headgasket? I checked and the engine oil isn't mixed with water.

A broken cylinder head. lets hope thats not the case

A few days back after changing the starter motor I took the car out for a spin, totally forgetting the cooling fan fuse had to be replaced since the original 60A fuse was broken. About 30 mins later the car overheated while I was stuck in the traffic and thats when I realized I didn't replace the fuse. drove the car back home ( I was just 10 miles away) maybe driving the overheated car 10 miles did some damage not sure tho. I kept stopping every 2-3 miles waiting 45 mins during the intervals to let the engine cool down naturally but ever since the engine oil has turned dark and the dip stick is very low on engine oil the DIC as well shows "low oil level" and oil temperature low message when I run through the options to check coolant temperature and battery voltage. Any help= highly Appreciated!

 

Are you sure your fan is coming on? If not, probably either a melted fan connector or bad ground.

 

I just had this happen on my 09 Z06it was a bad solid state relay switch on next to the fan. Info getting from computer to switch but not to fan. I also learned not to mix antifreeze types red/green gold as they have different corrosion inhibitors and when mixed can cause a jello slurry that can clog the system. Got mine to an engine builder who said springs in the head may be softer and piston rings may be warped. Good luck I feel your pain.

 

tell you mechanic do a 5 gas test .... sounds like a blown head gasket

 

The fan is not turning on despite a new cooling fan fuse [60A, #25 in the fuse box]. I let the car warm up for good 10 minutes then drove around the block, stopped, openned the hood the temp kept rising past 220 mark but the fan never turned on. And again as usual the water in the coolant boiled up and found its way out.

 

I been keep fillin' it with tap water didn't bother buying the coolant yet just waiting for the problem to be resolved before I flush the radiator and the cooling system and fill it up with the recommended coolant. But as of now its plain tap water. I keep fillin' it keeps spillin'.

 

Yea most likely it does, I removed the plastic covers over the heads and saw the stained head covers.

 

Fan connector is a VERY VERY common issue. It melts and then fan won't kick on. Unplug the fan and look at the connectors.

 

Yeah I had my connector melt..make sure it doesn't look like this!!

 

Alright the issue isn't resolved yet. The cooling fan runs (did a direct connection just to make sure it runs). Removed the thermostat as I thought it might be blocking the circulation but still no luck. The water starts spilling out once the car is warmed up despite the running fan.

 

I'll try bleeding the coolant system tomorrow. Once it's bled, I'll go ahead and have a look at the water pump and also install a new tstat. This should pretty much resolve the issue as I'm quite sure it's not the head gasket. I don't see any water spots or milky texture on the dip stick or oily texture in the reservior, I also don't notice any steam off the exhaust so I'm assuming it's not the head gasket

 

So I pulled out the waterpump, it looked pretty much waste. And here's the list of parts I'm done buying

1) New USMW waterpump
2) New Thermostat
3) New reservoir cap

Also done diagnosing the radiator since I had it pulled out. no blockage in the radiator whatsoever
I hope the new parts fixes the overheating issue. Any comments?

 

Presume when you direct-wired the fans the connector didn't look like the pic above from nick? Seems like you have the right parts, only caution is the burping isn't seamless (one-time only), may take a little extra to get the air bubbles out. Not unusual for many cars to.
So, you might be filling overflow, running, filling, running.

BTW, how many miles and what climate is car used in (desert, snow?)

 

Alright, I'm done installing the above mentioned parts (waterpump, thermostat, reservoir cap). The car is 71k miles and the car is used in a 105F climate. No the connector doesn't look like the above pic because there was no connector at all probably the previous owner got rid of his molten connector and just wraped an electric tape around .

Anyways back to the story. After installing the new parts the temp stays at 200F- 217FMAX (which I'm assuming is normal, or is it not??). Now the only problem, the fan is direct-wired. Since the overheating issue is resolved (pretty much) I need to get the fan work like the way its suppose to. Its a hassle to connect/remove the wire off the battery everytime I need to drive/park.

What could be a possible culprit.
1) The Siemens PWM Pulse Width Module (Fan controller)
2) ECM
3) Temp sensor

I welcome if there are any reference links on the forum. I'm trying to figure out the issue before sending it out to the dealer

 

Might look at post #12 here for insights from an actual fan mfr.

https://www.corvetteforum.com/forums...post1595557208

 

Fan is driven off ECU. So if the dash is reading correct temp, and tune isn't messed up, then only thing left is the PWM module.

 

How do you test the PWM? here's a link to my other thread where I've just specifically mentioned the fan & the module issue https://www.corvetteforum.com/forums...fan-issue.html

 

Thanks for the link. They suggest checking the harness and the controller(Pwm)