Sudden bad oil leak

Sandytows · January 9, 2017

Hi all. I am new to this forum but started having trouble with my truck and was hoping for some help.

In the last few days my truck has developed an oil leak bad enough to leave a small puddle on the driveway overnight, like maybe an ounce or two. I recently had some service done to the truck and I'm wondering if it's possibly related. I'll start out with the details and the background.

2007 Sierra 5.3 4x4 178k

I have owned it for 18 months and about 15k. The last couple oil changes I noticed a very slight oil leak on the right rear engine around the bellhousing. It was never enough to leave drops on the driveway just wet enough to make a nice cake of oil and road dust on the Bell housing. With the trucks age and miles I assumed the rear main seal was beginning to weep and didn't investigate further.

About a month's time and a thousand miles ago I had a lower knock sensor replaced cuz they were giving a code and check engine light was on.

My question: what are the chances this oil leak is related to the knock sensor replacmemt? I had the work done at a shop since it's a bit over my experience level.

Im in Maine it's super cold and icy here right now and I don't have a garage so I haven't wiggled under the truck to investigate but I can see that it's coming from somewhere near the back of the engine based on the puddle location under the truck.

Thanks for the help!

2000hdflstf · January 9, 2017

When you say right side, are you sitting behind the wheel or looking into the engine compartment ? And as far as the knock sensors concerned, they do not go into an oil passage.

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Colossus · January 10, 2017

Welcome to the board, Sandy.

Sandytows · January 10, 2017

Right side when looking forward. AKA passenger side. The knock sensor required a bunch of disassembly of the top of the engine as I was told. It was a lower one. Intake manifold I believe. Forgive me as I am not very familiar with this engine so don't know what all was disassembled. I did a little reading on forums prior to posting and read about a valley cover being involved possibly. The last time I took off an intake manifold was on a 390 Ford (25 years ago).

VikingTrad3r · January 13, 2017

Hi Sandy,

Yes getting to the knock sensors which are located on the top of the engine, one front, one back, you need to remove the intake and its possible that the rear of the intake manifold gasket is leaking.

Can you reach behind the valve cover on the head and see if you have an oil buildup on the rear of the passenger head? That will tell you if if it is a passenger side valve cover leak.