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BAD Oil Leak

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Old Apr 23, 2009 | 01:13 PM
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Default BAD Oil Leak

I have a bad oil leaking come from between the egine and trans. I took it to my mechanic and he replaced the rear main seal but when he started it up this morning it started leaking again. The leak wasnt as bad as before but it still leaked. Could any thing else cause it to leak from back there? I've read that there something on the intake that can cuase it to leak is this true?
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Old Apr 23, 2009 | 01:16 PM
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leaking a lot ? Oil pan maybe ?
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Old Apr 23, 2009 | 01:43 PM
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At first yes, it was leaving puddles like 6in x 6 in. After they changed it, it was still leaking but not sure if it was a little since the oil was low/
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Old Apr 23, 2009 | 01:53 PM
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Check your oil pressure sending unit.

Usually a rear main or oil pan leak will leave drips, because the gasket is still there, but its letting oil seep past. That fact that its a 6x6 puddle leads me to believe its not a gasket, unless the oil pan gasket blew out completely.

The oil pressure sending unit is located behind the intake manifold, on the top of the block. It looks like a round black tower. If they break or start leaking, they can make quite a mess since you have full oil pressure going through it.

Check that out, it sounds like it may very well be the culprit.
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Old Apr 23, 2009 | 02:25 PM
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Originally Posted by Wesmanw02
Check your oil pressure sending unit.

Usually a rear main or oil pan leak will leave drips, because the gasket is still there, but its letting oil seep past. That fact that its a 6x6 puddle leads me to believe its not a gasket, unless the oil pan gasket blew out completely.

The oil pressure sending unit is located behind the intake manifold, on the top of the block. It looks like a round black tower. If they break or start leaking, they can make quite a mess since you have full oil pressure going through it.

Check that out, it sounds like it may very well be the culprit.
Thanks for the input. I let my mechanic know to have them check that as well. Could the switching oil and adding an additive cause the leak to worsen? I was using high mileage oil before but I got a deal on some synthetic and added a can of Restore and that is when it started leaking a lot more than usual. Usually I always add Lucas; this time I didn’t add any but when it starting leaking I add some and it kind of stopped it or slowed it down.
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Old Apr 23, 2009 | 03:15 PM
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Guys i need help!!!!! Anyone!!!
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Old Apr 23, 2009 | 03:31 PM
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Originally Posted by lilpb1
Thanks for the input. I let my mechanic know to have them check that as well. Could the switching oil and adding an additive cause the leak to worsen? I was using high mileage oil before but I got a deal on some synthetic and added a can of Restore and that is when it started leaking a lot more than usual. Usually I always add Lucas; this time I didn’t add any but when it starting leaking I add some and it kind of stopped it or slowed it down.
A leak is a leak, especially one that bad. The type of oil and/or additives should have nothing to do with it.
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Old Apr 24, 2009 | 02:51 AM
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i was a mechanic for a long time before i joined the army and i would do what i always did. clean the entire area off hose whatever fill it up with oil and start it up and trace the oil leak down. if your mechanic cant fix it hes ****** sucks and you need a new one because diagnosing the problem is only the first step.. if he cant get past first base then he shouldent be playing in the big leagues
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Old Apr 24, 2009 | 03:25 AM
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Reach behind your intake on the drivers side and check for oil. If there is oil then it's your oil pressure sending unit.
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Old Apr 24, 2009 | 03:28 AM
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Picture of the sending unit

https://ls1tech.com/forums/9894589-post5.html
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Old Apr 24, 2009 | 05:00 AM
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Here's another thought. Maybe when it had a bad leak he didn't clean up the oil that was there previously. Could it just be residual oil still weeping out? Just brain storming a little.
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Old Apr 28, 2009 | 03:59 PM
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Originally Posted by Wesmanw02
A leak is a leak, especially one that bad. The type of oil and/or additives should have nothing to do with it.
EXACTLY...
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Old Apr 28, 2009 | 05:21 PM
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how about he plug in the crankshaft
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Old Apr 28, 2009 | 08:06 PM
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Is it a M6 or auto? If its a M6 it could be your slave. My friends was doing that. When we first put it on the lift, there was a puddle of oil and i thought it was the rear main but it turned out to be the slave.
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Old Apr 29, 2009 | 05:23 AM
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not to intrude but i just had my clutch done AND NOW MY CAR LEAKS im extremly pissed it my 2000ss has 60k and NOW IT LEAKS haha i just got heads and cam to go to the track but you cant run if you leak.... has anyone heard of leaking after a clutch install
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Old Jan 22, 2011 | 02:34 PM
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Could also be a porosity block leak... I had the same leak... I replaced my rear main and rear cover and continued to leak... So then noticed my cam sensor
o-ring was a little falt so i replace it and the oil sender while i had the
intake off... But then removed the tranny and let it run and found out i had a porose block, the repair is rtv for it.. There also a gm bulliten out for the same issue and has a repair guide for it.. Hope this helps some of you.
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Old Mar 1, 2011 | 03:15 AM
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my car does the same thing, my mechanic has seen it on alot of ls1's it comes from where the oilpan meets the block by the oilfilter housing there is spot in the oil pan gasket that takes most of the pressure and over times it seeps out. mine does same thing drips little drops in a 3x3 to 6x6 area going to get fixed this week
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Old Mar 1, 2011 | 06:33 AM
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Might be different, but mine was GUSHING between the engine and the trans, and it ended up being the Oil PSI sensor at the back of the block (just behind intake manifold). I guess I cracked it during intake swap and it finally let go lol. Got scared thinking it was rear main. May not be your issue, but to even check it I had it up on buddys hoist, with a mirror from underneath, PITA.

Edit : 94'BLKBRD beat me to it, didn't read that lol
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Old Mar 1, 2011 | 07:35 PM
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Check your PCV system....... a lot of times a plugged PCV system will cause rear main seals to blow because of excessive pressure in the crank case area because it is not being vented. Just saying
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Old May 11, 2013 | 11:46 PM
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Originally Posted by cjels1
my car does the same thing, my mechanic has seen it on alot of ls1's it comes from where the oilpan meets the block by the oilfilter housing there is spot in the oil pan gasket that takes most of the pressure and over times it seeps out. mine does same thing drips little drops in a 3x3 to 6x6 area going to get fixed this week
Did you you resolve this leak?
I'm having this area leak as well?

Where was it?
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