View Full Version : Overheated

05-13-17, 10:50 PM
I have a '16 Z06 with an automatic. I was racing in the LS FEST WEST Road Course Challenge in Las Vegas last week. After 4 laps the bells started dinging and I looked down and saw my coolant was 282 degrees and I left the track short of my allotted laps. Is there a "fix" for the overheating issue that anyone knows of? Either GM or aftermarket? I won't race again until something is done with the overheating of my Z.

Hib Halverson
05-15-17, 05:54 PM
Without having road tested your car, I'll guess that you are spending too much time at high rpm. That, plus the fact that automatics don't make the best track cars and the weather in Vegas might have been pretty warm, might be working against you.

If you plan to track regularly, you may need to adjust your driving style a bit. You may, also, want to change your engine oil and your coolant mix.

05-15-17, 08:35 PM
Would a normally aspirated engine overheated like that at high rpm? I was running Mobile 15-50 and I did change that when I got home. I didn't loose any coolant but should change it? I guess the only fix is to watch those RPMs and keep them down all I can next time as there doesn't seem to be a GM fix. FYI I don't have the Z07 package but have dot 4 in the brake system. I never did detect any brake fade and I was doing 123 mph on the back straight away heading into the first corner. It's quite a car, but pushing it hard will heat it up for sure. To me it seems like a design flaw as it basically is a "race car" that is street able but race cars have their limitations too. I went to the dealer when I got home and he said it wasn't throwing any codes. That evening, of the race, I drag raced it and it did great and then auto crossed it the next day. Seems to run great. Love that car but it can overheat for sure. A bigger radiator isn't a fix?

05-15-17, 10:15 PM
check Corvette Forum as massive thread on overheating issues and solutions folks have been successful with

05-16-17, 02:15 PM
Yes. Definitely check out the C7 section on Corvette Forum. Your issues are common.

I am a C6 guy myself but one gentleman that I follow on YouTube just added a larger coolant reservoir to combat similar circumstances.

Boston Joe 620

05-18-17, 01:01 PM
Overheating of the transmission, and sometimes the engine, is a huge shortcoming of the C7s, especially Zs. It happens frequently at track days, and even gearhead magazine tests. It's a pretty serious flaw for a car with the aspiations and mojo of the Vette. The last time I checked, GMs response was "let it cool down."..brilliant.

05-20-17, 02:47 PM
Whom is it at GM that I could get a hold of and, at least, get an answer as to "how to fix" the problem and worry about who's going to pay for it after it is fixed so I can race like I thought I would be able to in a Corvette Z06; Corvette's "race car"? Bigger radiator, different supercharger, bigger coolant reservoir, etc? Maybe the answer is, "it basically can't be fixed". At least I'd know where I am on the racing end of owning the car. It makes me hesitant to ever buy another new Corvette "race car" to race .

Hib Halverson
05-20-17, 10:10 PM
First, understand that the automatic powertrain generates more heat than does the manual powertrain. As current Corvette cooling technology has all the heat generated by the powertrain shed by the engine coolant radiator, ECT is a much more critical issue. 282°F is way too high for ECT under track conditions. Once you see ECT go past 250-260, I'd back off.

As to my earlier comment about RPM, with respect to track use, I was talking about part throttle operation. Often I see drivers going though part throttle parts of a course in two low a gear, such that their RPM is at the high end of the engine's torque band. That causes two problems: 1) it generates more heat and 2) it may put you at the wrong RPM when coming off a turn, for example: you exit a turn near redline in second when you should be near peak torque in third.

Now, as for simple changes you can make to gain a modest reduction in ECT: 1) use premium full synthetic lubricants rather than the blended or semi-synthetic lubricants which are factory fill in the engine and rear drive unit (RDU). This is because premium synthetics typically reduce lubricant temperature. Since all powertrain heat goes into the coolant, whatever you can do to reduced lubricant temperatures helps your coolant temperature problem.

For track use in the LT4, I'd use Gibbs Driven DT40 5W40. DT40 is an mPAO-based, premium full-synthetic engine oil. In the rear axle I'd use Gibbs Driven 75W110 Gear Lubricant. Keep in mind that a Z06 has an external, electronically-controlled limited-slip differential (eLSD) so the choice of gear lubricant does not need to be compatible with a traditional, internal limited slip. Gibbs Driven has a new ATF which meets the Dexron 6 specification but I could not find it on the Gibbs Driven web site (http://www.drivenracingoil.com/). For track events, that's the stuff to use your trans and you'll need to find a trans shop which will flush and refill your trans with that. I'd try calling Gibbs Driven for more info on getting ahold of some of that Dex 6 ATF. (704) 239-4401

As for coolant you should reduce the level of antifreeze in your coolant. I'd start with a 15/85 mix of antifreeze and water along with Gibbs CST additive which supplies the anti-foaming, anti-corrosive and wetting agent you need for track use. You also can go to straight water which is an even better coolant, but, if you do, you must use CST, you must change the coolant ever two years and you must not park or store the car anywhere that gets below 32°F

Also, I'd switch your charge air cooler coolant to straight water and Gibbs CST. Note that changing the charge air coolant is not an easy job. Special equipment is required to fill and bleed air out of the system.

Anything you can do to increase airflow through the cooling stack will help. Tape over openings though which cooling air can bypass the radiator. Remove the front plate if it obstructs air flow...stuff like that.

Beyond those things, you get into real money...a bigger radiator.

05-28-17, 08:37 PM
Thanks Hib. That's the most comprehensive answer I have read on the problem. I think by implementing your tips, I will be fine on the next rack event.

06-20-17, 11:17 PM
The more I read the more I believe that there really is a problem that shouldn't be there and certain measures can help with the overheating but won't really cure what is wrong, just appease it some. What makes the engine overheat? Water or oil or the supercharger and why? I know we have a water cooler, the radiator, but is there an oil cooler? If it was just a simple fix of a bigger radiator say, then are they putting a bigger radiator in the 17s or 18s? Was overheating an issue in the C6 ZR1? I don't think I ever read that it was so what is so different in the LT4 vs the LS9 engine? Maybe the best track car would be a C6 Z06 with a Lingenfelter power upgrade; no supercharger and 600+ horsepower!

06-22-17, 07:53 PM

A large group of 2015 – 2016 Corvette Z06 owners have filed a class-action lawsuit against General Motors due to a proposed issue where their Corvettes go into limp-home mode after performing on a race track where the engine temperatures rise to a certain level.The lawsuit, filed Tuesday, June 13, 2017 in the U.S. District Court for the Southern District of Florida, alleges that after around 15 minutes of track use, the Corvette Z06’s LT4 engine will go into “limp mode” due to a “defective cooling system” which prevents the driver from driving the car on the track until the engine has cooled back down. The lawsuit also claims that GM was “knowingly selling allegedly defective” cars, even though the vehicles are sold as track-ready.

CDR Wayne
08-13-18, 05:13 PM


I have had my Z06 go into limp mode at Daytona, Charlotte, Pocono, VIR, NCM, and almost every other track I've been on. The solution was always the same - paddle shift at 5000 to 5500 RPM to stay out of of the high rev range. It doesn't affect lap times much at all but it takes a little extra concentration to stay on top of shift points until you get to know the track.

Other Z06 owners would often mention that I should bleed the Intercooler system on the Supercharger to ensure there are no bubbles in the system. Supposedly, bubbles cause cavitation in the system and when that is sensed by the engine, it shuts off the electric circulation pump for 3 minutes. Never did confirm this. Maybe someone else on the forum knows.

I had my dealer bleed the system only to find out at Bloomington Gold from a factory rep that there is a special bleed tool for the LT4 and 5 engines that dealers can either buy or get on loan. Without it, I was told that it is impossible to do a proper bleed on the Intercooler. here is a picture of the Bleed IV as many people call it:


Then I found out that there is a fluid reservoir deep down under the hood where you can actually see if the fluid level is correct. I got this from the factory rep and we checked it out on a ZR1 which has the same reservoir. Here is where it is located. Bring a strong flashlight:




The correct fluid level is for two small bubbles to show about the size of a quarter. I've yet to track the car with a known proper fluid level but this could make a huge difference. By the way, all the bleeding was covered under warranty when I complained about overheating.

08-13-18, 09:07 PM
if automatic tran is builting heat put big tran cooler and that keep car coolant temp lower

CDR Wayne
08-14-18, 12:39 AM
if automatic tran is builting heat put big tran cooler and that keep car coolant temp lower

The transmission in my 2016 Z06 does not overheat at the track. I had a 2014 C7 Z51 and it did have transmission overheating problems. This problem appears to have been fixed in the 2016 C7's with an extra radiator under the grill. Engine coolant overheating and entry into 'limp' mode is the problem I am addressing with the procedures for the Intercooler bleeding.

11-18-18, 06:49 AM
The GM "fix" to the overheating situation was the ZR1 with its extra coolers and butt ugly front snout. There are aftermarket vendors that make conversion kits to cut the front end and add coolers to help but that fix is expensive. Best solution is to either not track the car or short shift it and run less than the 20 minute sessions you have paid for.