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2003 4.8 Starting To Leak Oil Rear Of Engine, Lovely!!


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With 162,000+ on the clock, my '03 Sierra 4.8 2WD has started an oil leak at the rear of the engine. Has anyone else had a similar issue? I am hoping against hope that it isn't the rear main seal, but with my luck it probably is.....

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Thanks for the replies guys. I went to take a quick look at it this evening, and couldn't even see it. Will hopefully be able to get more time and attention to it this weekend.

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I had a rear main oil seal leak on a 1995 Nissan pickup (at 90 k miles, out of warranty). Eventually it got so bad that I had a 6 inch diameter puddle of oil under the truck every time I parked it. The oil leak also ruined the clutch. It cost me $ 1,200 to fix that mess.

Edited by pm26
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It's probably the rear main seal but at your trucks age and mileage it's not surprising to have leaks. Soon you'l be having leaks from all of the gaskets on the engine.

 

I had my rear main seal done in 2011 when the transmission was replaced. Learn from my mistake and do as much preventative maintenance in that area if the tranny is going out. ie. mounts, seals, etc

Edited by white1500
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My neighbor is telling me that when the oil sending unit starts to leak, it will do so showing on the passenger's side of the engine (which it does).

 

I checked the oil pan bolts several months ago before this even started, just as a matter of mainteneance, and they were fine.

 

The original trans bit the dust back in 2010, and the $3000 price tag at the time from the dealer was bad enough.....

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My neighbor is telling me that when the oil sending unit starts to leak, it will do so showing on the passenger's side of the engine (which it does).

 

I checked the oil pan bolts several months ago before this even started, just as a matter of mainteneance, and they were fine.

 

The original trans bit the dust back in 2010, and the $3000 price tag at the time from the dealer was bad enough.....

 

The "oil sending units" are made of plastic (thanks GM), and because of where they are situated (due to heat), get brittle and leak.

 

I had one crack on Sara (2001 Z28), and your friend is correct, the leak appears to be down the backside of the passenger side of the block.

 

I had the sensor replaced, "and all was forgiven" :)

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  • 6 years later...
23 hours ago, CharlesC said:

The 4.8L and 5.3L engines are know for the Rear Main Seal, Oil Pan Gasket and a Bypass Block right above the oil filter to leak.

 

Question If you previously/recently had a rear main seal and all else above replaced and are encountering similar drip locations. You would  expect oil also be inside the inspection plate and covering everything flex plate, torque converter ect… in there, Or could the seal leak somehow bypass were you can see inside the plate and the inside remain relatively dry/clean?  My situation Is the inspection plate inside doesn't look like its leaking but the oil comes down the bell housing point and I can see drips on the starter and its side and oil filter and its side

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