Oil leak ?? Need a little help

[Dustin Butts]

OK I am a veteran of LS1Tech.com and I have done massive amounts of work on LS1 engines in camaros and firebirds and corvettes. I have not done any serious work on the truck engines. Also most of these F-body engines were fairly new so I haven't run into this problem before.
My buddy has a 2000 4.8 truck with 170Kmiles on it and it has a pretty decent oil leak at the rear. It has drips coming off the starter and at the middle right at thethe trans/block interface. We replaced the oil pan gasket and a friend at a trans shop pulled the auto trans and replaced the rear main seal and rear engine cover gasket. Still leaking but less. The trans friend said that it looks like the rest of the leak is coming from up top. I know there is an oil pressure sensor and a cam sensor and according to factory service manual diagrams there appears to be a non used hole with, I presume, a little tin button like an expansion plug pressed in there.
My question is what is the most likely spot for a leak up there? I am just getting some heads up before I get into this later in the week. I also would like intake manifold torque sequence and specs and any other land mines I need to watch out for for R&Ring the intake manifold on a truck. Thanks brothers..

D

[RedHeartbeat]

Oil sensor leak. That many miles of vibration has most likely desolved/killed the seal in it. Poke a flashlight and mirror down there and check it out. Better yet, pull the intake off and get direct access to it.

[txarkitekt]

Oil sensor leak. That many miles of vibration has most likely desolved/killed the seal in it. Poke a flashlight and mirror down there and check it out. Better yet, pull the intake off and get direct access to it.

My thoughts exactly. It would be wise to take off the intake to replace this sensor. Since it does have 170K, the underside of the intake manifold will be quite dirty. This will not only give you better access to everything, but it will give you a chance to clean everything well. As you know, the intake manifold gaskets are reuseable. Make sure to clean those well also.

[thunder550]

Also make sure it's not something simple like the dipstick tube seal. I searched and searched for an oil leak only to find that my dipstick tube was not seated fully into the hole.

[thunder550]

Here's a link for pretty much any torque spec you might need for the LS based motors.

LS1Howto.com

Intake Manifold Bolts (First Pass in Sequence) 44 lb-in
Intake Manifold Bolts (Final Pass in Sequence) 89 lb-in

For sequence I just start in the middle and work outwards in a star pattern.



9-----5-----1-----3-----7
x-----x-----x-----x-----x
Intake manifold
x-----x-----x-----x-----x
8-----4-----2-----6----10

[Dustin Butts]

thanks friends...good info