Starting Over: C7 Z06 Overheating Issues
 

I hope the mods will let this thread stand and not combine it with the great overheating mega merge. Given how that thread has gotten so confusing with a number of loosely or unrelated issues I wanted to start over and summarize at least my understanding from reading the other threads so new folks don't have to try to. I’m hoping we can keep this thread on track with a mature discussion of our observations to date with specifics. There are some details that I may have missed so please feel free to correct me and I’ll update this post.

There are at least 3 different heat related concerns that owners have raised about the C7 Z06 and heavy track use and I’m going to try to cover each.

The first is high oil and coolant temperatures that when either reaches a programmed threshold of 257F for coolant and 311F for oil will result in a message being displayed that the engine is over temp and to idle the engine. While I’ve not experiences first hand my understanding is that the car also goes in to so called “limp mode” where there is very limited power.

This issue appears to be most common on A8 cars when the driver leaves the car in “D” and the automatic shift logic holds the engine in lower gears and high RPMs for extended periods of time. Most owners have found that by manually shifting the A8 transmission while on track this issue can be avoided. Also, it is very uncommon for M7 cars to experience this issue in ambient temps less than 100F (SBC you’re the only person I can think of that we know is real). It’s also worth noting that the few instances of excess coolant temps on the street have been the result of mechanical failures of the car and not a systemic design flaw.

Some forum members have experimented with additional cooling measure to include removing the inlet scoop from the radiator to the hood scoop, removing the rear weatherstrip on the hood, and aftermarket radiators. At best it seems the results have been inconclusive so far.

The second issue is the electric power steering unit overheating on track. The symptom is that the power assist becomes intermittent and eventually turns off completely along with receiving a message on the display to service power steering. It is unclear why but this issue seems to be tied to running the air conditioner while on track. In the cases I am familiar with simply running with the A/C off will prevent the power steering from overheating. I’m not aware of anyone that has overheated the PS with the A/C off. Some folks have tried using spacers to allow additional air in the engine compartment from under the undertray but again I believe the results have been inconclusive so far.

Finally, there is the issue of the car losing power after extended tracking because of an increasing Intake Air Temperature (IAT). This is also known as heat soak. My personal experience has been that the C7 Z06 intercooler does a good job of managing IAT and the only time I’ve experience this issue was with rapid back to back sessions extending for multiple hours in ambient temps in the mid to upper 90’s.

Some might confuse this with a oil or coolant overtemp condition but in my experience this has occurred when fluid temps were still well below the maximum. The car still runs fine and can continue to be tracked, just without as much acceleration, and preliminary IAT data seems to indicate that the temps rise quickly when the car is stopped but then also drop rapidly once it is moving again.

Last, it’s worth noting that the C7 Z06 appears to be very sensitive to fuel quality. There have been multiple reports of cars entering what feels like a low power or limp like mode on track after adding questionable fuel. In these cases there is no message on the DIC and adding quality fuel and driving for a while seems to clear up the issue. I mention this simply because it might be confused with a heat related issue.

I’ve tried to fairly cover the input from those that have provided their personal experiences and been very specific about what I am basing solely on my experience. If I referred to you indirectly and you want to be named explicitly please say so, I simply didn’t want to start digging through the old thread to see who said what. Hopefully we can have a productive discussion from here.

<p>I think this is a pretty accurate summary. I have sorted through the long and complex posts and distilled it down to the same, editorial and speculation free, conclusions you have clearly outlined here.<br /><br />I think a new reader interested or concerned about the track use/temperature limitations that have been reported would be able to understand the issues with just this post. Thanks!<br /><br /><br />&nbsp;</p>

Sounds like a pretty good detail run through it all. Only exception i see is the power steering going out while tracking was done with the AC off in my car. I have never ran the AC while tracking. I have since been back to the track and ran 2 full days with no issues with power steering or any over heating.

I have ran many days with temps 95 to 99 degrees with never any engine coolant or Oil temp overheating with just the following mods.


My mods:
80/20 water coolant ratio
15w50 mobil 1
Rear weatherstrip removed
Home made heat shield between the cat and oil cooler.

It is dire for anyone tracking to change the coolant ratio and oil to 15w50 before tracking.

just like the owners manual says!

Great summary.

Mods - Please keep this thread unmerged, separate and alive.

Also - unless folks are posting PDR info, data, actual track observations etc. or questions/discussions about same, the posts should be deleted. It would be great to keep this 100% factual findings/experiences.

:iagree: 100%

I think that before we get into "my car did/did not overheat", we need to establish what we consider "overheating".

The viscosity design temps for the 5W-30 oil is at 212F. For the 15W-50 oils it is around 240-250F. I would say that anything approaching 300F oil is way overheating, even if you don't get the bells and wistles and the limp mode. The thinned-out viscosities of the 15W-50 oils at 300F are far below their temperature design parameters. The oil was clarly NOT designed to be run extensively under those temperatures, thus IMO, it is valid to call it overheating.

Coolant? I would say that anything north of 230-240 is overheating.

As to the statement that the use of 15W-50 oil off the track is "dire" I would take exceptions to that. I had run all my many high performance street and race cars with oils X-50 and never any engine issues. I am presently running the M1 15W-50 in my car full-time and expect absolutely no problems but only benefits, given how hot the oil runs under my regular mountain driving routines. I will switch to 5W-30 for the winter but, even that is not an absolute must, given the mild winter temps in CA. Most high performance engine builders will recommend oils in the x-40 to x-50 viscosity ranges for all-around usage.

Edit; one more thing to add; I am also active on the Jaguar forums having owned 6 of those cars, presently 2. The Jag 5.0 engines have water pump issues that can result in catasthrophic loss of coolant. A number of forum members posted that by the time they got the warnings, the engine was toast, warped. So, all I am trying to say that no one should use, or wait for, the visual or audio warnings as a sign of overheating.

Excellent summary! Thanks Poor-Sha. I was losing interest in the mega merge post that was going in every direction. Good job

Phil

Hi

You may want to look at https://mobiloil.com/en/article/why-...oil-protection to get more accurate figures.

Kind regards

My experience, I received my car in December and after the 1500 mile break in I started tracking it, I went through the cooler winter months with no issues and was breaking all of my pervious C6Z06 times. I was having a blast and enjoying my new car. I was reading post about heat soak and bla bla bla. I started defending the car and posting numerous threads with PDR and data showing the car running very fast times on my home track Sebring.

Than 85 degrees with 100% humidity and it all started going bad, I could overheat the car in as little as ten minutes, all backed up by PDR and data all buried somewhere in the megamerg. I started documenting my overheats by taking my car to the dealership, at this time I started a dialog with the GM engineers through emails with the dealership as the liaison. We/they/I could not resolve and I was voicing my displeasure to he point of I was getting rid of my car and buying something else. Problem was, I loved my car and really just wanted it to run right. anyway after many trips to the dealership/track GM decided to replace my fuel pressure regulator switch and reflash/recalibrate my ecm, at the same time I had the "Willow Springs Rough Track Calibration" done.

I really cant say or tell you guys what fixed my car, what I can tell you is that I can now manage my water temps and run m car for 30 minute sessions. Can I run it at 9/10's 10/10's? No (or at least not more than a couple of laps than cool it down). Can I run it at 8/10's and have fun, still running faster than I ever could in my C6Z06, Yes.

So in summery should GM come up with a cooling pack? Yes, should GM be let off the hook? No, can we enjoy our cars? Yes.

I do believe that SBC's car needs to be fixed, and I do believe that PoorSha got a true Gem. As a side note I do believe I would have beat his VIR time if I didn't screw up and wreak my car. :lol:

Your numbers are in need of some adjustment. The coolant temp warning is at 256 degrees, not 265 degrees. I think those warning temperatures for coolant and oil are crazy high, and only for the Corvette have I ever seen such extremely high temperatures set as limits. Any other car would issue warnings far below those temperatures. There isn't an oil company in the world that would recommend running their oil on track at 320 degrees.


And while you may not have had any overtemp warnings. I can easily overheat my Z51 and get an "Engine Overheating - Idle Engine" warning as the coolant temperature gauge just keeps rising and rising until it reaches the red zone and then the warning comes, even in sub 86 F ambinet. The Z51 and Z06 have the same radiator. Plus my M7 transmission temperature gauge gets pinned in the red zone at 300 F virtually every session. GM has no fix, I've been dealing with them about this for over a year.

Poor-sha..

Excellent summary. I had overheat issues at Mid-Ohio amd VIR. I have made the mods that are on lawdogg149 list, but did not have a chance as yet to evaluate their effectiveness.

I am seeking a documented solution, not anecdotal information or speculation. I would prefer not to hear from those in this thread who do not track their '15 or '16 Z06s. I would like to hear some answers from GM other than, "We are aware of the problem, and are looking into it." Finally, I am anxious to hear from DeWitt who is the only one I know that is seeking a radiator/oil cooler improvement. Hopefully, DeWitt will have successfuly tested his approach to the problem and document the differences no later than October 1.

I agree with Poor-sha. We need a dedicated and focused thread to address a resolution to this issue.

Sir Just curious if your C6Z was stock or modified. Also what is your opinion of the handling and power delivery of the two cars? Obviously there is a big hp and trq difference but would think a heads and cam C6Z would be close in power.

Yes my C6Z was stock. best ever 2:22. C7Z started at 2:20's. It is not a power issue, It is a balance issue, the C7 is so much better in all aspects, braking, cornering, exit speed. In my option if GM had put a 605HP LS7 in this car it would have been amazing.

I assume you are referring to this sentence from your quoted link?

"Mobil 1 advanced synthetic motor oil provides outstanding high-temperature performance and is proven to protect at engine temperatures up to 500°F."

"Engine temperatures" vs. "oil temperatures" are two very different concepts. No sane engineer would recommend running 500F oil temps. As a matter of fact our car's oil temperature gauge goes into RED over 290F. So, at the extreme, we should consider THAT to be a deifnite "overheat" value even though by that time the viscosity of the 15W-50 oil is thinned out to be nearly the same as 20 and 30W oils, loosing all the benefits of the higher viscosity rating. Like I said, the 15W-50 oils ideal running temperatures are 240-250F.

Nobody recommends running on the track with 300F oil temperatures. Some people do, some people get away with it but, IMO, it is playing Russian roulette with the engine. I personally refuse to do it, I back off before my gauge gets to 290F, which happens within a few minutes of hard, high RPM running.

We got to strive to come up with a fix that gets our oil temps down to 240-250 max and our coolant temps to 210-220F. The only solution that is clear to me is a dedicated air-to-oil cooler and, potentially a new radiator. First, I want to try the oil cooler as it may significantly drop the water temperatures, once the heating effects from the superheated oil is removed from the coolant circuit.

:iagree: and thanks for the excellent summary.

Most of this post is opinion backed by no data. If you are going to state such opinions, perhaps you should qualify them by stating your qualifications to make them. Otherwise, they are worthless and without merit.
Your comments regarding what constitutes "overheating" are nothing but your opinion unless you can provide data to support them.
That is what this thread should be about. Facts rather than bullsh$t opinions, supposition and theories based on nothing.
S.

Excellent summary, Poor-sha.

Agree 100 percent. ^^^

The point is to gather data to help manage heat and get the most out of cars under extreme conditions.

As to the original poster's first point, last weekend I saw a Z06 overheat (boil-over) with an ambient temperature of about 80 degrees (medium humidity). The car was a manual. It had done a couple of laps about 15 minutes earlier and had done two laps following me (in my Z51) when it started having the problem. The engine did NOT self destruct, just seriously over-heated and had to be flat-bedded to the dealer.

I should remind everyone that each individual incident is unique. Its possible that this particular event was cause by some failure and not a general over-heating problem. So don't take any one incident of proof for or against anything. Its only by analyzing the root cause of all the incidents that any over-all problem can be proven.