ticking/knock noise
Good luck with whatever path you decide to go down.
I have owned the car since day 1, and except for very rare and very short duration trips by my kids ( a single trip to the grocery store by my better driving daughter and son) I have put probably 164.75 of the 165k miles on it. Oil level has never been low, so unless an internal blockage leading to localized starvation has occurred, that's not an issue. Same with overheating - which is what my favorite mechanic said caused oil to look like that. I guess a blocked galley could lead to local effects on the oil, resulting in breakdown. Never seen low oil pressure, and although I have had an undiagnosed slow coolant loss issue, I have never seen the engine temp read above 212. Always have used Mobile1, and have followed the dashboard-indicated intervals - which makes me think the 10k plus interval as shown on the dic are probably not realistic...
My friendly mechanic, an old European car specialist, said he'd never seen so much sludge buildup. This friend suggested a letter to Mobile1 manufacturers, as he thinks these long interval oil life recommendations are misguided.
I am doing a pretty thorough top rebuild (cleaning up valvetrain, head surfacing, new lifters and springs) but to dig into the block??? not sure I really want to go there without a definite goal in mind. I am more inclined to go with above recommendations to run some high detergent oil/additive for a few cycles, drain, rinse and repeat till it comes out clean...
1) External leaks
2) Internal leaks i.e. coolant in the oil, buring, etc.
...and yes, coolant in the oil will create sludge.
If you have that type of sludge build up, and don't see that as a problem that warrants a rebuild at 165K miles............good luck with that.
Addendum:
I now am certain that there is a small pinhole leak of coolant into the oil system, probably in the block somewhere. When I did the pressure test on the cooling system via a pump/cap on the overflow tank, there was no external leakage, and no drop in pressure. But would one expect any drop in pressure if the leak was very small - say, a few teaspoonsfull over the 12 hours I had the cooling system pressurized? Of course not - that much volume loss would make no difference in the pressure. But over time, those teaspoonsfull become pints, and quarts of coolant, and the result is large amounts of sludge buildup. Case closed.
If my car had 65k miles instead of 165k, I'd replace the engine. But I think I'll try a can of stop-leak. I was hesitant to do so before, but now I see that as the only realistic way to possibly get to 200k on this motor.
Last edited by portney; Aug 20, 2012 at 07:30 AM. Reason: additional thooughts

Started in 3 seconds of cranking, and I ran the engine for 20 minutes to bring it to temp, with generic (Advance AP)5W-30 oil, and a Fram Ultra filter. Revved it a few times, then shut down and drained immediately (lots of suspended particulates in dark brown oil), then added Pennzoil Ultra, and a high capacity Bosch filter.
Drove normally for 1000 miles, including short runs to work and back, around town, and one 300 miles round trip at normal (79 mph) speed. Added one can of Gunk engine flush, and ran (not drove) for 5 minutes at temperature, drained. Oil was dark, but not black, and no particles settled out in clear class container of captured drained oil.
Mobile 1 5W30 and another Bosch high capacity filter installed.
Now have about 1500 miles since rebuild, and it looks like coolant level is holding.
Plan is to drive 3-5k, then change again.
I changed the oil on the C-5 over the weekend, because it was relatively warm, with colder weather in the near future. As I had mentioned earlier in this discussion, I had used Pennzoil Platinum last summer, and my engine seemed quieter. When I put the car back on the road this year, I put Mobil1 in it, because I still had some left over from a big sale that Wally World had 2-3 year ago, when I bought something like 18 or 24 quarts.
Autozone has an internet sale going on currently, 5 qts. of Pennzoil Platinum, and a K&N oil filter for $32. (you place the order online, and do a pick-up at the store) I put the Pennzoil in on Saturday AM, and have driven the car around for the last 2 days, and once again, just as it did last year, the car seems quieter.....
BJs has a deal on Shell Synthetic, might be time to try something different.
Did Exxon-Mobil change the formulation of Mobil-1 some time this year??
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Driving to the gym this morning, car suddenly, and with a loud "thud", lost power to the rear wheels. Engine running fine, able to shift, and seemed at first like the problem was the clutch. Now, after putting it up on the lift, and noodling around a bit, seems more likely the problem is in the transmission.
Since engine is running well, and in addition, she has new tires, new seats, and recently rebuilt top half of engine, I am facing the age old dilemma - replace transmission(2004, manual transmission with 165,000 miles), only to have more issues in a few months, or just give up??? The car is the best one I've ever owned, and I do not want to get a new one. It is old, and a paint job is in order, but otherwise, all systems are good.
I love this vehicle, but should I just give up? I guess my specific question/need for advice concerns cost. How much will a new/rebuilt transmission cost? Is replacement a reasonably doable thing for a weekend warrior? Anyone out there done this in their garage?
If this post should be put in a new thread, please let me know, or admin take care of it...
DT MacMillan


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Transmissions don't usually give up all at once with a "thud". It usually starts with an annoying whine, that gets increasingly louder.
With respect to your car, if it's in good shape, body and interior wise, and you really like it, it might be worth looking for a good, honest, and reasonable Corvette mechanic. Sometimes, repairs can be more cost effective than selling off.




Yea mines only in the mornings after sitting over night, once the engine warms up I cant hear it. What brand oil do you use? Can you get the ZDDP at an automotive store or do you have to order it online? I'd like to find something at a store as I'm doing the oil tomorrow. I've also heard using a higher flowing filter like k&N helps a little.
















