Oil Leak What Should I Check?

[Daniel644]

My Sister in Laws Parents have an early 2000's (like 03-05, I don't remember the exact year) Suburban with the 5.3, last year (like i'd say at least a year ago) the oil pressure sending unit (on the back of the block behind the intake manifold) failed and I replaced it, recently the suburban has been having an oil leak, he thought it was the rear main, but I reached back to where the oil sending unit is and came out with oily fingers, I also noticed at the front of the engine on top of the valley (basically in front of the intake manifold) looked a little oily.

Aside from trying to see if I can tighten the oil pressure sending unit a little more what else should I look at to see for possible oil leaks on the top of the motor? I haven't spent much time around the V8's i'm more used to the 4.2 in the Trailblazer so any advice would be appreciated.

 

[Mike534x]

If you're finding oil near the oil pressure sensor, then its mostly likely coming from the cam position sensor. It sits between the heads, and is located at the back of the block behind the intake manifold (same general area as the pressure sensor). Best bet would be getting one of those little borescope cameras ($18 bucks on Amazon, and plugs into your phone if its USB-C) and snake it back there to see if there's oil coming from where the cam sensor is.

Be prepared to take the intake off if thats where the leak is, and since you're going through the hassle you might as well replace the knock sensors while you're there to avoid doing the job again in the future. They do sell replacement o-rings for the cam sensor, if you wanna avoid buying a new one, and having go to the dealer for a CASE relearn.

 

[azswiss]

Check the valve covers as well. While you are there check the PCV hoses (at the front of the passenger valve cover & at the back on the driver side) for any cracks.

 

[Daniel644]

@Mike534x thanks, actually ordered one of those camera's last night figuring it would make it easier to look around different places, I also bought a pair of "kevlar sleeves" (well thats how they are marketed) that should help make it easier to reach back there without scraping up my arm on the intake so I can clean the area off to make it easier to see whats leaking.

@azswiss will do.

 

[Daniel644]

Pretty sure I found it, I located both Oil Sender and Camshaft Position Sensor with the endoscope camera and then I had him crank the truck up so I could watch for an active leak, this is that video

To me it looks like its seeping out between the metal and the plastic parts of the oil sender.

 

[Mike534x]

Seems like it could be a faulty oil sensor! Did you use an OEM one, or part store one?

 

[Daniel644]

Seems like it could be a faulty oil sensor! Did you use an OEM one, or part store one?

OEM AC Delco based on the part number.

 

[Mike534x]

Its hard to tell, but it looks like the leak is coming from where the sensor mates with the theaded portion. I'd get another and swap them out and see if that works.

 

[Daniel644]

Its hard to tell, but it looks like the leak is coming from where the sensor mates with the theaded portion. I'd get another and swap them out and see if that works.

Got the new one installed earlier today while I was over there, as for the old sensor, you could take the metal part the socket fits on in one hand and the plastic part the wire clicks into and rotate the plastic half relative to the metal half with relative ease, so i'm pretty confident that was the problem. Guess we just got a crappy one last time. Man I wish Engineers had to work on the cars they designed, LOL. I mean the sensor itself is easy enough to replace, it's just in the worst possible position making you slice up your arm doing it.

 

[Mike534x]

At least it wasn't an expensive fix, sometimes you get a bad quality part. When dealing with a recent faulty knock sensor on my TB, the AC Delco ones I purchased were both faulty out of the box. Bought a delphi one and its been fine ever since. If that intake didn't sit so far back, that sensor would be a cake walk to replace.