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Rear main seal leak?


Rabid Farm Hand
12-31-2011, 11:14 PM
I have an '01 with around 180k miles on it. It has an oil leak that shows itself on the lower aft end of the engine and bell housing area, and lately it has been getting worse. I thought it was the rear main seal, but after cleaning it off and observing it more, it seems to be coming from somewhere else. And I'm pretty sure it's not the intake area or the valve covers, or anything that high up on the engine. The oil is all over the the aft lower part of the motor and then onto the bell housing and trans where if it were a rear main seal it would be more localized to the bell housing and aft. I was wondering if the 5.3's are prone to an oil leak in that area and if anyone knows a sure fire way of detecting a rear main seal leak, just so I can rule it in or out. Thanks for the help.

MT-2500
01-01-2012, 09:15 AM
I have an '01 with around 180k miles on it. It has an oil leak that shows itself on the lower aft end of the engine and bell housing area, and lately it has been getting worse. I thought it was the rear main seal, but after cleaning it off and observing it more, it seems to be coming from somewhere else. And I'm pretty sure it's not the intake area or the valve covers, or anything that high up on the engine. The oil is all over the the aft lower part of the motor and then onto the bell housing and trans where if it were a rear main seal it would be more localized to the bell housing and aft. I was wondering if the 5.3's are prone to an oil leak in that area and if anyone knows a sure fire way of detecting a rear main seal leak, just so I can rule it in or out. Thanks for the help.

Clean off old oil and run engine and watch where it is starting to leak.
If any covers on bell housing remove them to look inside.
Does it have a oil filter and or oil sending unit or oil lines on rear of engine?

They make a oil leak checking dye to put in engine oil to find where it is leaking.

Let us know what you find.

Rabid Farm Hand
01-03-2012, 01:28 PM
After cleaning all the old oil off with degreaser and doing a thorough rinse, I ran the enigne for a little bit to warm it up to check for the leak. It leaked from the bell housing at about the oil pan and down, even through the inspection plug area. The starter had oil all over its mounting hardware and motor. It is a significant leak leaving a good size oil spot/puddle on the carport floor. After a little reading up on the issue, it seams the rear main seals tend not to leak, but short of having to take the transmission off to verify on a engine with 180k on it, what othe way can I verify? It started off as a small amount of oil on the bottom of the engine and trans and has now turned into full blown puddle. Any help or suggestions with be apprecitated.

j cAT
01-03-2012, 01:53 PM
After cleaning all the old oil off with degreaser and doing a thorough rinse, I ran the enigne for a little bit to warm it up to check for the leak. It leaked from the bell housing at about the oil pan and down, even through the inspection plug area. The starter had oil all over its mounting hardware and motor. It is a significant leak leaving a good size oil spot/puddle on the carport floor. After a little reading up on the issue, it seams the rear main seals tend not to leak, but short of having to take the transmission off to verify on a engine with 180k on it, what othe way can I verify? It started off as a small amount of oil on the bottom of the engine and trans and has now turned into full blown puddle. Any help or suggestions with be apprecitated.

what year vehicle/engine ? rear main seal on the 5.7L does leak . I use a engine oil sealer of just a couple of ounces , and this usually takes care of it. this is something that occurs with the use of regular dino oil that breaks down sooner than synthetics.I think the O rings on the 5.7 filter housing can be the cause as well.

with the newer 5.3L this can be the oil pan gasket/or the O rings on the filter housing to block..

try the oil sealer first.

rather than solvents to clean It is best I found to use steam with NO SOAP . this is very safe and fast. allow to dry completely before operating the engine. if a distributor cap is used remove wires and cover with plastic ...

solvents attack rubber/gaskets/seals/corrode wire connections etc...

I forgot to mention that the crankcase vent system must be working. the PCV and all hoses must be checked for proper operation. on newer engine this may require the removal of the internal PCV in side the valve cover...

gmtech1
01-03-2012, 02:29 PM
Sounds like a pretty bad leak, under pressure. The oil pressure sender/switch is in the back of the intake manifold, hard to see and get to. Check that, if it were leaking, it would run down to where you are seeing it.

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