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2004 Z06
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Discussion Starter · #1 · (Edited)
I purchased a 2004 Z06 that had been sitting in the previous owner's garage for 9 years. So far I have accomplished the following:

Spark Plugs & Wires: No noticeable differences. I changed them prior to using Techron Fuel Injector Cleaner.

Chevron Techron Concentrate Plus Fuel System Cleaner: Very noticeable performance difference. No more lean fuel codes, sulphur exhaust smell, or rough idling. Had increased acceleration and lowered the idle. I tried this out prior to going into full diagnostics to find out why the codes/smell/idling problems were occurring.

Belts: Replaced the serpentine/AC belts. No major improvement but engine seems to run 'smoother.'

Radiator Flush - Followed GM's directions on flushing the radiator. Replaced upper/lower radiator hoses along with a thermostat. No noticeable improvement in performance.

Differential: Changed. No noticeable difference.

Transmission: Changed. Shifting gears 1-4 has improved and smoother but 5 & 6 are still 'slotty" and still having difficulty hitting R consistently.

Power Steering: No noticeable differences.

Turn Signal Fluid: Much more consistent flashing with brighter and more fun colors.

At a later date I will take care of bleeding the brakes and change out the clutch fluid.

It has an aftermarket Vortex Ramair Induction Cold Air system which I plan on removing and reverting back to the stock air filter system. Personal choice.

On a side note: When reading forums, I am surprised at the frequency of maintenance work that some do. Changing out the fluids at intervals that seem unreasonable. Radiator, differential, transmission, and power steering once a year; brake and clutch fluid every other oil change, are just a few of the examples.

EDIT: 10/25/22:

I updated the above work in the order in which they were completed and added a bit of additional information.

Stock Air filtering system: Removed aftermarket Cold Air system and replaced with factory air assembly and filter. Though not dyno tested, but seat of my pants tested; the car runs much smoother and acceleration is better. Also, it is running much quieter.
 

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DC PIT CREW BOSS
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My '04Z gets gas and washed 2-3 times a year maybe. The rest of the time I drive it like I stole it
 

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2004 Z06
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64 Posts
Discussion Starter · #4 ·
Yeah. I plan fully bleed to old fluid out.

It just amazes me at the amount of money wasted doing ‘maintenance’ that isn’t needed.

With the differential change out GM recommends driving it reasonably for 300 miles. Until then, I’ll be gentle. LOL.
 

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I do not question the obviously reasonable actions posted. especially the belt replacement.

I once bought a used car that ran fine around town, but after a couple of hundred miles of high speed driving to visit a friend in another town the belt just separated into pieces on the highway going home. And of course, it was one of two possible belts for the car, and the remaining pieces of belt gave no clue , plus it was a "W" belt, not the more common old V shaped belt, and there was no internet to help with antique car problems. Live and learn, an once of prevention is worth a pound of cure, all that stuff applies.

I do offer that the cost of replacing the radiator is very reasonable, and might be worth considering during this renewal, since the plastic that makes them light and somewhat inexpensive, doesn't last forever, and is known to have a common weak spot up on the left hand top side. my new GM radiator lowered operating temps by five degrees from what I assumed was the original part from 03. My area has very hard water, which probably contributed to scale build up, if it found its way into the cooling system of my used car. I prefer premixed solution, because of the filtered water used in the jug.

another thing , if the under supports are all bashed up from crashing into parking stops over the years, when the radiator is out would be a good time to replace them, but that part costs about as much as the radiator. I wish I had known to replace mine when I had the radiator out, mine are kind of messed up, but not enough to make the effort as a single repair.
also, the GM radiators are now universal, and no longer have a dedicated plastic bottom molding for each model's hose configuration, if you are building a show car.

I am also just starting to undertake refreshing my old car , I am going to risk some long distance touring, so will be undertaking pretty much the same actions.

You might have thought it too obvious to mention, but I put in new plugs and wires when I first acquired my used car, in large part because the job was so simple, and I thought it beneficial to have a known starting point on these somewhat consumable wear items , even though the correct plugs are now spec'ed for 100,000 miles, so not a real critical concern. I just did it for peace of mind. the stock GM stuff , with the red wires , is usually agreed to be the best choice, and fits perfectly.

I did benefit from using the newer spark gap recommendation, as the plugs in there had the older gap, and the newer gap gave a slightly better idle. I wasn't expecting some screwy plugs selected because the previous owner always used those plugs , as some guys posting like to insist is the best way to go , because my used car was professionally maintained, but you might want to check , depending on your assessment of need.

if you do change out the wires, note that they are only very slightly different, because of the independent coil locations. Don't be like me and just pull them as though it were an old style V8 and the length of the plug wires is easily self evident and you needed a new puzzle to occupy some time.
my new plugs were delivered, and might have been bounced around, because two out of the eight plugs that supposedly come correctly gapped out of the box, were incorrect . I corrected them under magnification, because of the danger of marring the finish and creating a second spark path. which I assume is why they now are sold as correctly gapped out of the box.

I wish you happy motoring with your new ride .
 

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2004 Z06
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Discussion Starter · #7 ·
@bodysurfin child: I updated my OP by adding a few things that I had not been listed. I did change out the wires & plugs. Thanks for the feedback on the radiator... I will take that into consideration but as of now there are no leaks and the temp is running within the GM parameters,
 

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1972 Convertible, 2004 Coupe, 2019 Grandsport
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The C5 is a great platform! We've had an 04 coupe since new and now has 260k miles on it. You're on a good path with everything you've mentioned. You stated that you've seen posts of more frequent changing of fluids Etc., could be they are tracking the car which requires a more frequent change schedule, also some are hung up on old school change every 3k. Stick with recommend oil and if you need piece of mind do oil analysis Blackstone Laboratories I've done this with 04 and a 19 Grandsport that I track and the cars oil moniter system is spot on. Enjoy!
 

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2004 Z06
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Discussion Starter · #9 ·
The C5 is a great platform! We've had an 04 coupe since new and now has 260k miles on it. You're on a good path with everything you've mentioned. You stated that you've seen posts of more frequent changing of fluids Etc., could be they are tracking the car which requires a more frequent change schedule, also some are hung up on old school change every 3k. Stick with recommend oil and if you need piece of mind do oil analysis Blackstone Laboratories I've done this with 04 and a 19 Grandsport that I track and the cars oil moniter system is spot on. Enjoy!
Some were Trackers but most were regulars. I just can't understand why someone would do regular maintenance so frequently.
 

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Yes pennzoil makes their synthetic oil from natural gas. Synthetic base stocks are cleaner and have much better lubrication so oil change intervals have increased.
Plus fuel injection is a much more precise delivery system so you don’t have as much fuel contamination of the oil. This also increases oil life. So 3k oil changes are a thing of the past. I personally do a 6K oil change. I just can’t bring my self to go 10k or longer.
 
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