GTM overheating; blue light; 'limp mode'

[GTM0176]

My GTM has problem of overheating, going to 'blue light ie engine problem' then going into engine limp mode. Oh, by the way, it is over 100 degrees here in Phoenix, many times 105 , 110, 115 .
Working on solutions. Do Arizona owners have similar problem? Wonder if completed car ever tested here in summer.
Any solutions from fellow GTM owners!
GTM 0176

[jason moore]

the l6 or l7 is a corvette engine front mounted and my c4 had a chev truck water pump wow not cool take this engine and do a mid engine covert and the air flow is even more stuffed a higher flow water pump or a speed of plus 100 should correct the problem I WAS IN PHOENIX AT NIGHT AND IT WAS 126 THATS HOT MORE WATER MORE PUMPING AND there are coolant additives that also will bring the temp down

[LCD Gauges]

What is the cooling system pressure? What is the cap pressure rated at?

[kabacj]

I have raced at 100 degrees air temp and the car ran fine using the truck water pump and a standard c5 corvette radiator.

I would check the basics first. Make sure you don't have any air pockets in the system. Air in the system is the most common problem.

I added a bleed valve like you see on a brake caliper in the water pump housing and a custom overflow can in the engine compartment just to make the air bleeding process easier. Neither are required to get the system working

Make sure your radiator is in good shape. ( not corroded or blocked)

Water wetter and pure water offer the best cooling capacity but obviously no freeze protection.

Also make sure the engine is not running too lean. A lean condition will make it harder for the cooling system to keep up.

Hope that helps.

John

[crash]

We just ran a race in 105 degree temperatures with no over heating issues. Fans are important. Make sure they are operating as intended by GM. Stock GTM water line routing leaves something to be desired. My opinion is that every GTM should have a header tank system in the car, like every other car on the planet has, but I may be biased since I sell those retrofit kits.

http://www.myraceshop.com/Header_Tank.html

[Edgeman]

When you installed the hard coolant lines, did you installed as in the manual. If you did you will have the small line going to the suction of the pump and your pump will not be circulating proberly and could be cavitating. The bigger line should be your suction and the small one will be the discharge. Having mine set up this way, once I had it purged I have never opened it again and never had it air lock problem. I did not have to install an extra expanson can (header tank) in the back, I only had the one in the front from the corvette.

[fastthings]

I have been driving in near 100 temps, mild shake down driving. I see temps on the gage around 220, and it doesn't seem to mind. I do run two duct fans that point out the back.
I always run around 200 for my other cars.
It has never gone above 220.

Is 220 safe all day long?? is 230 safe all day long?? I also think my gage reads 10 degrees less than the ecu.
I am new to the LS world, I'm looking for you guys to tell my to quit worrying.
What temp would you guys shut-er down?

[fastthings]

I don't think my car would make it at a red light, if it was 115 degrees out. That might be some kind of a limit??

[crash]

220 is the optimum operating temperature. Most street cars aim to have their engines run between 200 and 225. Above 230 and bad stuff starts happening unless the cooling system is built to handle it. Above 220 will require a high pressure system to work properly, and the stock Vette plastic tanks will not handle that increase in pressure for very long. Should be able to keep the temp at or below the 220 mark on a GTM if everything is working as intended and the system is void of air.

[flickery8]

I have had several overheating episodes. I believe it is due to the difficulty of getting all the air out, especially after overheating the first time. I also have found water wetter to make up to a 10 degree difference and that is the cheapest/easiest solution to run while the air works its way out.

[mikespms]

I have been driving in near 100 temps, mild shake down driving. I see temps on the gage around 220, and it doesn't seem to mind. I do run two duct fans that point out the back.
I always run around 200 for my other cars.
It has never gone above 220.

Is 220 safe all day long?? is 230 safe all day long?? I also think my gage reads 10 degrees less than the ecu.
I am new to the LS world, I'm looking for you guys to tell my to quit worrying.
What temp would you guys shut-er down?

Hey Gene,

I have a similar issue,after the cam change and tune the exhaust temps went up drastically but the car was not overheating. It stayed around 200-212 deg during tuning and it made good power but after the dyno it was stalling at idle after fast deceleration it would start right up and idle fine but if you slow down too fast it would stall. After the body went on the temps went up, in traffic it would go to 220-230 deg and the stalling got worst. When the car was hot idling temps around 220+ if I opened the hood the temperature would go down to 200 deg in a few minutes. So i figured it was an airflow problem I tried removing the grill and making the openings on the hood vent bigger but it didn't do much. I was running the stock corvette radiator and fans so I upgraded the radiator ,fans and a new hi flow mechanical water pump I also vented the radiator compartment into the wheel wells. That helped but it still gets to 220deg with the hood closed in traffic but it take much longer to happen and if I open the hood it goes down to 189 deg in minutes. I also spent some time with the tuner or I should say tuners The first guy was not too helpful gave me the runaround and excuses,the second guy got it to idle better but not right he runs a trans am race team his son is t/a2 national champ and he is on the road most of the time and don't have the time to mess with it but he raced c5 and c6 corvettes and gave me a ported throttle body from one of his old race car that help some, he said that the cam lobe separation of less than 114 degs made his race cars run hot and hard to idle to much overlap unburnt fuel to the cats =hi exhaust temps.I checked with comp cams and they confirm the diagnosis by saying that the cam I used has 112deg lobe separation it gives the rough idle sound that people like but it's harder to tune to idle and they would custom grind a cam with 114 deg lobe separation with a high rpm power band to match the porsche gearing and would idle smoother for $400.00 dollars.
I have done some research on the tuning and cooling system, Jim from factory five recommended an inline electric circulation pump he said that it solve a similar problem on the 818r. I was referred to a new tuner by a friend that had dyno and they confirm the electric circulation pump is the way to go, they used them on the high hp turbo set ups to get proper flow to the intercoolers and radiator. The engine driven water pump does not flow enough at low rpms that combined with the long run of the tubes to the radiator restricts the flow through the radiator. I am going to try an electric inline circulating pump and before any more tuning or cam change removing the cats may do the trick on the high exhaust temp.

[kabacj]

Do you guys know what the input temp and output temps are across the radiator?

I am using a stock c5 rad I got from rock auto with the stock c5 fans.

When they kick on the return water is so cold it shuts the thermostat.

When I first built the car and was purging the air I could not get enough flow because the stupid thermostat kept closing

Just wondering if you use a doner c5 rad and then Amp up the power and heat load with a hot cam if that's the issue.

If we could compare our temp drop across the radiators we would know if the radiator itself could add to the problem.

[mlkwd1]

My GTM was purchased out of AZ and has no overheating issues despite have and enormous amount of HP. Apparently when it was built it did overheat so here is what the builder did to help with that situation. Hope this helps.
The fans run all the time and the thermostat control the temp at 210-220. The A/C solenoid on the ¾ line going to the coolant tank is disconnected and failed open to always allow flow. It has diffuser louvers from VRaptor and rear deck diffusers. It also has the rear quarter windows removed and CF NACA ducts installed. The Kooks headers have been ceramic coated and the cats gutted. It also has a Trans oil cooler and pump and an oil cooler both mounted in the ducts in front of the back wheels.
This winters’ project will be to return the fans to running on temperature control and installing a header tank from crash so I can utilize the a/c heater core shutoff solenoid and make the A/C cooler. Right now the electrical draw is excessive with all the extra stuff running when the starter is engaged. It drags the voltage down too far. I will also take the tunnel apart and better insulate the cooling lines and install the VRaptor louvered panels on the belly pan.