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Official Announcement of The C8’s 7.18.19 Reveal; Video of The C8’s Ride; C7 Production Ending This Year

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C8 Section Re-Organization, With Our New “Mid Engine Exterior/Interior Pictures, Videos and Renderings” Section

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Your C5 & C6 Issues: Ask “OffshoreMechanic2

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  • Your C5 & C6 Issues: Ask “OffshoreMechanic2

    Hello my name is Jim J. I work on a Offshore Platform for a Major Oil Company, I own a 2004 White/Oak Convertible & 2008 Victory Red/Cashmere Coupe!.........I repair my own cars and have plenty of experience and very knowledgeable mechanically on C5 and C6 Corvettes.

    **If you have any issues or questions about your C5 or C6 please contact me.....I would like to help!


  • #2
    Thank you Jim for your skills and reaching out to others who might need your assistance. This thread is going to be so valuable to so many C5 & C6 owners. I have just “stickied” it so it remains at/near the top of this C1-C6 section — easy for folks to later find.

    Nice also that those who might have some C5 or C6 issues, can also visit this thread to see if their issue has been earlier asked/answered.

    ​​​Thank you Offshoremechanic2!
    So many questions about the ME right now, but the answers are nicely, though slowly, coming out.

    Excited owners of a 2015 Z06. Lifetime, annual contributors, and 20 year members of NCM. Our 2020 ME C8 Corvette is next.


    • #3
      Hi Jim, I need to replace some cooling components on my 99 Z51 M6 daily driven coupe with 140k. The engine is modified, (heads, cam, intake, exhaust, tune) but still naturally aspirated. This summer in traffic with the A/C on the temps eventually climb to 255 before I intervene, either by turning off the A/C and using the heater, or getting the thing above 50MPH. I have the original stock radiator, water pump, 192 degree thermostat, overflow etc. After trouble shooting, the fans are turning on as they are supposed to, but the drivers side fan is getting weak, and the rad has lots of scale. In addition, the overflow tank has a tiny leak around the hose nipple.

      So, here are my questions. I have around 450HP now, won't ever get more than 500. I drive hard on the street, and like to autocross. Do I get a stock replacement radiator and replace the fans with stock, or should I step up to the Dewitt direct fit aluminum radiator with the spal fan setup that I see everyone selling. When I do this, should I change to a lower temp thermostat and have the fan operation modified in the computer or stick with the stock temp. It seems now that the engine works best at around 190 to 200. Is there any advantage to replacing the stock overflow with the aluminum one from Canton? Finally, when I replace the hoses is there any advantage to silicone hoses other than making my wallet lighter?

      I've owned the car since 2008, and just last year it has become my only car. I will put 20k a year on it til I'm buried in the darn thing, so I'm really interested in reliability above all else.

      Thanks for your help. I'm not into bling, just performance and reliability. I have enough money to maintain the car (I have a $150 a month tire and brake budget), but don't want to spend money just cuz I have it.

      Thanks for your help, Kent


      • #4
        Hey Kent,
        Have a solution for your overheating problem. I have a friend of mine who had the same problem and we resolved it with the following . I would go ahead and purchase the Dewitt Radiator( you will have to call Dewitt and find out what part number you need to order that will except original GM cooler fan) SecondIy purchase a new Dorman Products p/n 634-634 OEM Cooler Fan Assy. to replace your week fan assembly.Thirdly purchase a new AC Delco coolant recovery tank p/n 10405218. Next I would stay with the 190° thermostat Lastly Since you have a modified engine this item allows you to turn on the high speed fan manually either racing or just cruising( Sac City Corvette High Speed Fan Controller - Coolit H2/H3 ....You will have to go to sac city Corvette website and determine which one of the two page 2/H3 that you need).

        This will solve your problem of overheating my friend races and also uses his 99 Corvette as a daily driver as well he has had no problems since we have modified his car with the above listed.
        contact me if you have any further questions


        • #5
          Hey Kent...sorry if the reply was rather short(but accurate) but I am in Tampa on vacation with the family. Any further questions I will reply when I get back home!



          • #6
            Hey Kent......have not heard from you , was the reply positive or negative, do you have any questions or suggestions????


            • #7

              I am a friend of Kent’s; he is pretty sick right now. I can tell you that just before getting sick, he was so excited by your advice, that he bought every single part you suggested. He can not wait to get better, have the parts arrive, to install them, and to resume his daily driving and his autocrossing.

              Thanks Jim for being so helpful to Kent!

              So many questions about the ME right now, but the answers are nicely, though slowly, coming out.

              Excited owners of a 2015 Z06. Lifetime, annual contributors, and 20 year members of NCM. Our 2020 ME C8 Corvette is next.


              • #8
                Thanks for the offer to lend insight on c5and c6s...

                i dont have any questions at the moment but do appreciate the offer for the future.

                very cool of you



                • #9
                  Hey Jim. Am in the middle of assembling the parts you suggested. Can't wait to get them all in! I ordered the V2 Cool-it from Sacc Corvette parts, and it's a really nice piece! Beautiful craftsmanship, awesome instructions, and it didn't work. Called the guys and they immediately sent out a replacement, and after a 5 minute install this one works as advertised. I already am in much better shape cuz of that little item, so looking forward to next week. The Dorman fan assembly is part number 620-634 by the way. Thanks for your help, I'll post when all the parts are assembled.


                  • #10
                    Offshore - I've got a question for you relating to the C6. I've got a 2010 Lingenfelter ZR1 that I've had since it was new. It's modded, obviously, but it's a fairly mild bump = 710 hp. I kept it at that level, as opposed to going higher with LPE (and they certainly have the ability to go wild and build absolute monsters) for a couple reasons. One is I love the darned thing so much I intend to keep it for good long time (already have had it 8 years now), and relatedly, I wanted to extend the longevity of the factory cats, which it still has. It is street driven, tracked, and I run high speed events with it.

                    I've thought about, for purposes of the high speed events, having LG Motorsports (cuz they're fairly close to me), put on long tube headers and high flow aftermarket cats, re-tune it, and turn the wick up a bit more. The only reason I haven't done this, is I keep hearing folks say the longevity of aftermarket high flow cats is inferior to factory cats, and the factory cats get toasted at power levels higher than mine.

                    So - I can either leave it like it is, which is a rig that is deadbolt reliable and will embarrass a stock C7 Z06, or I can turn it up a bit more. But the latter path must solve the cat question, because while my state doesn't sniff cars, I'm not interested in running catless, due to the smell.



                    • #11
                      OnPoint.....Good Afternoon! With your C6 having all those fine mods 710 hp Wow! I am not going to lean either way on this’s strictly your choice. My expertise is more repair and troubleshooting, I prefer to stick with what I am sure about!



                      • #12
                        Offshore. I understand - and thank you. If you run across what you'd regard as reliable info on this topic, feel free to drop me a note. I've frankly heard conflicting advice on this.

                        Be safe out on that rig, my friend.


                        • #13
                          Offshore. As most everyone knows, there was a bad batch of valve springs that found their way into the LS6 on 2001-2003 Z06's. Do you know the serial number or production date that the new "improved" springs were first installed and/or how to identify them. The ones in my 2003 are are not the infamous "yellow" springs that broke so easily but rather are unpainted metal. I do not have enough history on the car to know if they are original or replacements. Any help is appreciated as I want to keep the engine absolutely stock if possible.
                          Thanks for your help, George


                          • #14
                            Hope your valve spring are the “best” ones George!
                            Last edited by John; 08-29-2018, 08:03 PM.
                            So many questions about the ME right now, but the answers are nicely, though slowly, coming out.

                            Excited owners of a 2015 Z06. Lifetime, annual contributors, and 20 year members of NCM. Our 2020 ME C8 Corvette is next.


                            • #15
                              Hey Rebelraider4.......listed below will answer one of your questions(vin # and year of engines built w/ yellow springs).......GM replaced the bad yellow springs w/blue painted springs......found there is 1 spring kit available GM 12499224(includes all 16 springs) GM 12625033 are the same identical blue springs(just sold individually)
                              What year they started manufacturing the new improved blue springs to sure!

                              Hope this helps!

                              Attached Files