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Old 06-19-2014, 04:58 PM   #1
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C7 Engine Oil Leak started

My C7-Z51 has 2,300 miles on it and I discovered engine oil on the floor a couple days ago. I'm taking it into the dealer next Tuesday. The mystery is up until now there has never been a leak. I park in the same spot in a garage with painted floor so I would know if and when oil leaks show up. The leak is in the front of the engine and dripping down the metal brace which is sticking through the plastic covering under the front of the car. I discover enough oil to make a spot about 3 inches in diameter. Since I discovered this oil I have not seen it again and I drive the car every day. The oil level is fine so it can't be leaking much. Hopefully the dealer can figure it out.

My question has anyone had oil leaks and, if so, where did the leak come from?
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Old 06-20-2014, 04:26 PM   #2
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Yep, I've had that issue

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This was after one week and less than 500 miles. So far it looks like some MORON at MOUNTAIN VIEW CHEVROLET in Upland overfilled the Z51 during the PDI.

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This is a picture the next day AFTER THEY FIXED IT!!!!!
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Old 06-24-2014, 03:51 PM   #3
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Ok here is the answer. I went to the dealer today. the oil is leaking back to the air filter assembly box due to the PVC valve. The reason is (according to Chevrolet not the dealer) at 2,300 miles my Z51 is not broken in yet. They say it takes at least 4,000 miles to break in (which is not listed anywhere in the owners manual). The dealer was instructed not to touch my car other than order me a new air filter. Granted the oil leak is very small but what else are they not telling us about a car that costs $70k? They claim that after say 5,000 miles I still have a problem come see them. For more on this issue it is Corvette forum under "vert major oil leak" many people on the Corvette forum have installed a catch can. According to my dealer this is not necessary has the problem should go away at 4-5 thousand miles. We will see.
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Old 06-25-2014, 11:50 AM   #4
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The problem with this oil being sucked into the intake is it carbons up your intake valves. And with direct injection, no gas goes past the intake valves to help wash it off before it's baked on. A catch can on your PCV system would help. I've got 6k miles on my C7 (no catch can) and theirs no sign of oil in the intake yet.

It sounds like a lot of blowby past the rings, pressurizing the crankcase, causing an excessive amount of oil to be sucked into the PCV valve.
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Old 06-25-2014, 12:15 PM   #5
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this is not a DI or catch can problem...it is a clean side separator problem, but you don't even need that...

I can tell you EXACTLY what it is...Chev and the techs have not thought out the proper levels in the reservoir -
1. drain the oil and add 9.5 QUARTS - NO MORE...and you will never have this prpblem again...and your air intake will stay clean....the car is BURPING....
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Old 06-25-2014, 01:23 PM   #6
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Quote:
Originally Posted by Glen e View Post
this is not a DI or catch can problem...it is a clean side separator problem, but you don't even need that...

I can tell you EXACTLY what it is...Chev and the techs have not thought out the proper levels in the reservoir -
1. drain the oil and add 9.5 QUARTS - NO MORE...and you will never have this prpblem again...and your air intake will stay clean....the car is BURPING....
I tend to agree with your analysis
So this is a Z51 issue due to dry sump system?
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Old 06-25-2014, 01:35 PM   #7
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Yup....a complete overfill....not a leak, an overflow....and again, chev info is bad....

You can run any car a qt down and have absolutely no problems unless you're doing some type of Daytona track work… there are thousands of cars out there running 2 quarts down right now and are not blowing up . Chev, and every other company has to put in a safety margin.. My car takes 7 quarts as a base car. I put in 6 quarts and a week later start putting into ounces to bring it up to 25% of the dipstick.

You can run a car a qt down with no problems but you run a car a qt over and you got immediate problems

This information was taught to me by powerhead engineers at BMW and Porsche when I worked for both them on the corporate side.

And all it takes is a bit less in the reservoir to solve this, not even a qt. get a turkey blaster and take out 3-4 oz......prob solved....
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Old 06-26-2014, 02:24 PM   #8
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I didn't know he had overfilled his car with oil. He said it checked ok. I own a C7 Z51 and I run it at the full mark on my dipstick. (I change my oil) And it takes about 9.3 qts to put it there. (including filling the filter first) I run my car hard on occasion and no leaks or burps. 6100 miles so far. Wonder why some do it and others don't. And I don't sell catch cans. I was just trying to be helpful.

http://forums.corvetteforum.com/c7-g...separator.html
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Old 06-26-2014, 04:22 PM   #9
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That's the point ....some are putting in 9.8 per chev docs, in one version of the manual it says 10 something, both are too much. And many are not fully drained, so its an overfill.

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Old 06-27-2014, 04:57 PM   #10
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C7 Engine Oil leak started

I found this bulletin from GM today. They state there are two reasons for oil in the air box:

1. Oil too full

2. Aggressive driving with low miles on the car.

I'm not the only owner in the world with this issue. Granted I may have been aggressive but after 1,500 miles I thought I was OK. Chevrolet says it takes 4,000 to 5,000 miles to break in the motor.
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Old 06-27-2014, 06:53 PM   #11
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Yup, that's been on the other site before. I predict it'll be followed by another that takes the oil level fill down .5 qt.....if so, it will be the third spec change. As it is, the aftermarket vendors are making hay on selling clean side seperators.
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Old 06-28-2014, 05:38 AM   #12
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Glen e - I am the idiot that started this whole thread. I tend to agree with you. My question to you is after dropping the oil .5 quarts you have had no problems? How many miles on your car? Are you aggressive on the car periodically? I am taking the car back to the dealer on Tuesday. They had to order the air filter. They are going to change oil, clean things up and put in new air filter. They are going to allow me to watch the mechanic open up the air box is I can learn and do it at home. It looks like its tricky with the antifreeze line running across it. My car has the original oil and the factory level was exactly at the full mark. Not too much or too little. I was checking it after 7 minutes which seemed to be the right time to wait after full warm-up. At the same time I did have visitors over Memorial Day and took folks for rides and showing off with about 2,000 miles on the car. Could be some blow-by too. I will know more when we get the air box open and see where the the oil is coming in from.
To be prudent I guess it is best to wait until I have 5,000 miles before I step on again. Thanks to all you guys with the helpful information. You are all great.
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Old 06-28-2014, 08:50 AM   #13
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I don't have a z51, but have owned dry sumps before......just going from my 35 year experience in the car/motorcycle industry on the corporate side. My "solution" is not a permanent one - GM needs to figure out why the car "burps" so hard. My gut tells me they just have published a suggested level # that is too much. Being a reservoir, and not the true level needed to lubricate, taking the level down a bit so it does not overflow into the airfilter makes sense. Going down a few oz in the reservoir so it does not overflow will not hurt a thing, lubrication-wise as the actual lubrication is injected.I certainly don't see a clean side seperator being needed if it does not over burp.

As I said above, a powertrain engineer from Honda Motor once told me to keep watch over my level, and keep it in the bottom 25% of the hash marks to prevent this sort of thing.

Last edited by Glen e; 06-28-2014 at 09:01 AM.
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Old 06-28-2014, 10:59 AM   #14
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I'm wondering if the fact Z51's have the dual oil pump causes some turbulence in the reservoir as it is constantly returning oil from the pan. A lower fill level would seem to lessen the effect of this?
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