Oil leaking options...hear me out first

[Mr T]

Folks:

So 2008 6.2L is going strong. Past year it does leak when oil is hot and all around the engine block (back side) by drain plug, starter motor and oil filter.

I replaced my drain plug. I've replaced the oil pickup gasket last year, which required oil pan being dropped. I put new oil pan gasket on and applied RTF at the back corners, etc.

I replaced both valve cover gaskets. Still dripping.....

I used RTF to seal up the oil cooler blockoff plate. WOW, that stopped all leaks on the left side. So clearly time is working against this engine and things are leaking. So now leaks are just on the passenger side by the stater motor--I think.

I opened the inspection plate at the tranny, thinking might be a rear main seal issue. The pressure plate/flywheel is dry. NO oil in that area. So I'm not sure it is rear main seal.

So my question is why would there be a leak near the starter motor? Where is there a seal there?

Secondly, is there anything above the starter that could be leaking? I thought there might be a knock sensor there or something......

Thoughts anyone?

 

[Danny3737]

The quickest way that I find leaks is to clean the area first with some greased lightning then run the engine for a bit, then use a boroscope. You can get them cheap off eBay, they are great for anything from auto to home repair.

https://www.ebay.com/itm/352477906922

 

[OR VietVet]

May have a leaking oil pressure sender at the back of the engine, if is located at the same area where the 5.3 engine sender is. Back of intake?

 

[wjburken]

May have a leaking oil pressure sender at the back of the engine, if is located at the same area where the 5.3 engine sender is. Back of intake?

This would be the first place I would look based on what was shared.

 

[Mr T]

I’ll take a look there but the oil sender unit is on the driver side and most of my leaks are on passenger near the starter motor. But it’s a process of elimination. I know.

 

[OR VietVet]

Think of it this way. Like water that drips on to something and then that water runs across the surface or down the surface and ten finally drops to the ground a hole foot over from where the leak started at. Same with oil, especially hot oil.

 

[Foggy]

Crank Position Sensor !! Near and above the starter. It's just an O Ring
that seals it into the block. New Sensor comes with new O ring

 

[iamdub]

My two guesses are crankshaft position sensor and oil dipstick tube.

Like Danny said- clean it off so it'll be easier to find the fresh leaks. I like to use brake parts cleaner- the cheap Super Tech from Walmart works great. Their engine degreaser works great as well.

 

[kbuskill]

Crank Position Sensor !! Near and above the starter. It's just an O Ring
that seals it into the block. New Sensor comes with new O ring

This was going to be my suggestion as well.

 

[PG01]

What those guys said... plus what pnwvet said....path of least resistance.... look up from where it’s dripping and try to follow it ....after it’s clean

 

[kbuskill]

The other option is to add an oil compatible UV dye to the oil and then clean everything up really good and crank the truck and break out the black light and start looking for the glowing dye.

 

[Mr T]

Do any of you know what’s above the starter motor? I really do see most of it around the motor and wonder if there is something above it. I will buy the die kit and try that but I fear it will be coming from above the starter and so perhaps have to remove it to see what’s above.

My current oil is at 10% so I’m changing it shortly. That’s a good time for the die—before the change.

 

[91RS]

Oil pan gasket and probably a rear main seal/housing gasket.

 

[PG01]

Do any of you know what’s above the starter motor? I really do see most of it around the motor and wonder if there is something above it. I will buy the die kit and try that but I fear it will be coming from above the starter and so perhaps have to remove it to see what’s above.

My current oil is at 10% so I’m changing it shortly. That’s a good time for the die—before the change.

 

[iamdub]

Do any of you know what’s above the starter motor? I really do see most of it around the motor and wonder if there is something above it. I will buy the die kit and try that but I fear it will be coming from above the starter and so perhaps have to remove it to see what’s above.

My current oil is at 10% so I’m changing it shortly. That’s a good time for the die—before the change.

Crankshaft position sensor:

That bronze cylindrical object underneath it is the solenoid located on top of the starter


Close-up view:

Angle showing more of the starter:

Bonus pic with starter removed, also showing nearby dipstick tube:

IMO, the dye is to help locate small leaks. Yours sounds like it's fairly prominent. Grab a few cans of brake cleaner and some goggles and spray away the mess. It takes seconds. Start it up and look for the new trails of oil. You may need to hold the revs around 1500-2000 for a minute or so to get the pressure up, simulating normal cruising pressure. Driving can make it difficult to find the origin since the wind circulating through the engine bay can blow the oil in other directions.


Oh- Please don't follow the Oil Life Monitor. Change your oil more regularly or, if you insist on following the monitor, change it when it's down to 50% or 30% at most.

 

[Mr T]

iamdub: Thanks for your details. Great pics. That shows me exactly where the sensor is. I am NO fan of replace and pray. I like to find issues, diagnose them then address/repair. So I wish I could clean all around and even at the sensor but I do think I can't get to it with the starter there. So perhaps I do have to remove the starter motor to get to the sensor. Once there, can't monitor it when its running so perhaps this is the case of replace and hope.

As for frequency of oil changes, this debate of oil usage, brands, frequency is long debated. Sure, always best to replace frequently as it lowers risk of issues. Just how frequent is the debate. However, I've always used conventional (not synthetic) on this car cause that is what the manufacture asked for and going to Syntheic would likely cause it to leak even worse...... I do run Synthetic in all my other cars as the manufacture requires it (Hondas). On '08 my GMC I have 198K on the 13 year old engine. So I'm confident in saying going to 10% of life hasn't caused my rings to go bad as she blows no smoke and fuel economy as stayed the same for all 13 years. Now has it caused my seals to leak (well some are right now), I would suggest that age is the cause of that and not oil usage. Most 2008 and older are leaking. It's a GM thing and at some point, that's what cars do when they get long in the tooth. Right....to this point....

It would be curious to know if we have any 200K 2008 owners (6.2L), who run conventional, change oil more frequent than the oil life monitor--who have NO leaks under the bottom. If that is you or someone, please share.

BTW, I seldom, if ever, get to 0. Usually drop it around 10%. Oh and my leaks are about 3 to 4 drips after every drive cycle. I used a tinfoil bottom (turkey baking pan) to capture it for 6 months. I caught probably 4 oz of oil over 1/2 a year or driving. So not the end of the world but I hate the mess.

 

[iamdub]

iamdub: Thanks for your details. Great pics. That shows me exactly where the sensor is. I am NO fan of replace and pray. I like to find issues, diagnose them then address/repair. So I wish I could clean all around and even at the sensor but I do think I can't get to it with the starter there. So perhaps I do have to remove the starter motor to get to the sensor. Once there, can't monitor it when its running so perhaps this is the case of replace and hope.

As for frequency of oil changes, this debate of oil usage, brands, frequency is long debated. Sure, always best to replace frequently as it lowers risk of issues. Just how frequent is the debate. However, I've always used conventional (not synthetic) on this car cause that is what the manufacture asked for and going to Syntheic would likely cause it to leak even worse...... I do run Synthetic in all my other cars as the manufacture requires it (Hondas). On '08 my GMC I have 198K on the 13 year old engine. So I'm confident in saying going to 10% of life hasn't caused my rings to go bad as she blows no smoke and fuel economy as stayed the same for all 13 years. Now has it caused my seals to leak (well some are right now), I would suggest that age is the cause of that and not oil usage. Most 2008 and older are leaking. It's a GM thing and at some point, that's what cars do when they get long in the tooth. Right....to this point....

It would be curious to know if we have any 200K 2008 owners (6.2L), who run conventional, change oil more frequent than the oil life monitor--who have NO leaks under the bottom. If that is you or someone, please share.

BTW, I seldom, if ever, get to 0. Usually drop it around 10%. Oh and my leaks are about 3 to 4 drips after every drive cycle. I used a tinfoil bottom (turkey baking pan) to capture it for 6 months. I caught probably 4 oz of oil over 1/2 a year or driving. So not the end of the world but I hate the mess.

Spray it clean through the fender well. With the wheel removed, you have straight access to seeing the sensor. You may not even have to clean it first. Hit it with a bright flashlight and you might be able to tell for sure if it's leaking just by looking.

 

[Larryjb]

Diagnosis using dye is a great idea, as is replacing the easy-to-get-to gaskets first.

One thing though, just because you couldn't see any seepage at the rear main doesn't mean oil isn't leaking there. I couldn't see oil through my inspection plate, but I had replaced pretty much every gasket and it was still leaking, so I bit the bullet and did the rear main. What I learned is that the rear cover can leak more than the rear main, but you cannot see it through the inspection hole.

And just to throw the monkey wrench into everything, my crankshaft sensor was probably the only gasket that wasn't leaking.

Also, depending on the age of the vehicle, if you are going to remove the starter to get at the crankshaft sensor, I'd consider getting a rebuild kit for the starter. They're easy to do once you have the starter out. I work slow, and it only took me about an hour to actually rebuild the starter. It would probably take everyone else around here about 1/2 hour or less.

 

[petethepug]

Oil leaks are handled like a maintenance issue on our 6.2. The longest I’ve had the motor leak free was 3.5-4 years.

NNBS have aged to owe the owner 2 or 3 rear main seals depending on the miles and year manufactured.

At 140k mi the 2nd rear main leak occurred on our 08 Denali after only 40k. We did the pan gasket at the same time even though it was intact. The oil temp sensor died shortly after that. Now I know it’s prudent to replace that when the rear main is being done.

So, pick your fight with your accessibility issues on the motor. If your wallet allows, look into all the high dollar labor issues (motor mounts) at the same time. When it’s time to deal with exhaust leaks and broken studs, it’s nice to have all that out of the way.


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[91RS]

There’s no reason a rear main should have needed doing again after only 40k miles if it was done correctly. Did they replace the whole rear main housing or just the seal itself? The gasket for the housing leaks just as much as the seal itself.