Rear Main Seal Oil Leak

[RetiredMD]

After discovering oil on the garage floor beneath my 2010 6MN Coupe (18K miles), the car was evaluated at Dale Earnhardt Chevy where a diagnosis of a rear main seal leak was made.
What might have caused this? I have had Red Line oil/filter changes every 3K miles at Cox Chevy and with every change the car was overfilled with 6 qts of oil. I was always reassured that the extra 1/2 qt. did not pose any problem, however, might this have caused the rear main seal leak?

 

[catbert]

First, I'd have a real problem with a service department that routinely overfills the crankcase after an oil change. I would never take them seriously again.

Rear main seals should not leak after 18,000 miles. I would take my car to a good independent mechanic to verify the diagnosis if the car is out of the warranty period. If it really is leaking, then you can proceed with the replacement.

 

[Chevy Customer Service]

I am not able to offer technical advice but I would be more than happy to check your warranty availability for you. If you would like to private message me with your vehicle identification number and mileage I can let you know all the expiration dates/mileage. Hopefully this will help,

Kelly J.
Chevrolet Customer Care

 

[Hib Halverson]

There's been a lot of discussion around the I'net about later LS3 manual wet sump engines.

If your engine is an LS3 manual with wet sump oiling–ie: no dry sump tank under the hood–adding six quarts of oil overfills the engine by half a quart.

While common sense dictates that half a quart overfill should not fail a main seal, there seems to be some anecdotal info out there suggesting it can.

If it were my car, I'd order the dealer to replace the main seal under warranty and instruct them to fill the engine with 5.5 quarts of oil. If they tell you the extra half quart doesn't matter, disagree and demand they do the job right or find another dealer.

Lastly, if you are using Red Line, but changing every 3000 miles you're doing nothing but wasting money and oil. A 3000 mile oil change for an ester-based synthetic does not improve durability at all.

Run Red Line until the change oil light comes on (typically about 10,000 miles) BUT, change the filter twice–that is change the filter at 50% oil life and 0% oil life.

 

[pkincy]

Although you will not likely find this helpful, remember the famous old saying....."it is not a SBC if it doesn't leak at both ends."

I certainly have found that true on my SBCs, my LT1s, my LS1s and my LS2s. Haven't gotten there on the LS7 yet but then again it only has 6800 miles on it and the leakage from my older cars makes up for this one being dry underneath.

Perry

 

[catbert]

Guess I've been lucky. Eight Vettes, and not a leaker in the bunch.

 

[Hib Halverson]

Although you will not likely find this helpful, remember the famous old saying....."it is not a SBC if it doesn't leak at both ends."

I certainly have found that true on my SBCs, my LT1s, my LS1s and my LS2s. Haven't gotten there on the LS7 yet but then again it only has 6800 miles on it and the leakage from my older cars makes up for this one being dry underneath.

Perry

Come on, Perry...it's just that you keep putting those motors together with used main seals or something.

I've built small-blocks and big-blocks with the early-style two-piece main seals and if you install high-quality rear main seals and install them properly, they don't leak.

My 1995 LT5 has never leaked a drop from the rear main. The only oil leak it's ever had was from a loose driver-side chain tensioner. Tightened the bolts and the leak ended.
My 2004 LS6 has never leaked a drop.
My 2012 LS7 (13K-mi. so far) has, also, not leaked a drop.