Oil Drip from PCV/Intake issue? Anyone experienced this?

[MLRTYME]

Hey all,

I have a 2007 Yukon Denali (6.2L, no AFM) and I recently rebuild the engine (approx 4200 miles ago). Full rebuild w/ new pistons/rings, lifters, main/rod bearings, timing gear, oil pump, rebuilt heads...etc...etc. I recently went on a longer trip than normal and saw oil dripping from the sway bar after it sat at home for about 20 min. I see oil along the back of the engine and it seems to be coming from ABOVE the oil pan. I pulled an inspection plate and the bottom of the transmission bell housing is dry as is the flexplate (which would lead me to believe not a rear main seal...I thought I installed that VERY CAREFULLY). I cleaned the entire bottom of the engine with brake cleaner, put it on ramps to get a better view, and let it idle and periodically hold at 1500 rpm and 2000 rpm (total for approx 10 min). I see NO oil coming from around the pan, nothing around the oil cooler block-off plate, nothing wet in the bellhousing, but I do see some forming on the drivers side rear of the block where the 'pad' is.

So, I thought that maybe I lost a seal on the oil pressure sending unit, a leaky valley cover, or a bad valve cover gasket. I checked the VC gasket carefully and can see no signs of a leak. I tore into the intake...and there is a decent amount of oil in each runner. So much that the #5 and #7 runners actually seemed to have oil 'weeping' out of the gaskets and down the back of the valley cover. All Valley Cover bolts are tight and there seems to be no oil coming from the Valley Cover - Oil pressure sending unit connection. All intake port bolts were tightened to spec upon install. I cannot confirm if I have the newer 12570427 valve cover, as I honestly didn't know to look for it when I rebuilt the engine. It does have a brand new Melling oil pump advised for the VVT in that engine so it pumps at a slightly higher pressure than what I had when I bought the truck with 129k on the clock. When cold, it will run 40psi at idle and when driving at 1500rpm after just warming up it will hit 60psi.

I can see oil in the runners. I know I need the updated Valve Cover (The oil deflector at the pan was installed during the rebuild). However, has anyone seen oil buildup via PCV so bad that it bypassed the intake runner gasket and ran down the back of the block enough to pool and cause a substantial drip all the way down to the sway bar?

Basically my question is this: Do I keep looking for other areas where a leak may be? I'm not sure where else to look, honestly. No Service Engine lights. I need to get this resolved so I don't have the damn oil spots in my garage anymore. This is ridiculous for 4000k miles. Grrrr.....

 

[02Lightning]

I have a similar leak that I can't pinpoint, a mechanic looked at it and told me it was a head gasket.

 

[Geotrash]

Hey all,

I have a 2007 Yukon Denali (6.2L, no AFM) and I recently rebuild the engine (approx 4200 miles ago). Full rebuild w/ new pistons/rings, lifters, main/rod bearings, timing gear, oil pump, rebuilt heads...etc...etc. I recently went on a longer trip than normal and saw oil dripping from the sway bar after it sat at home for about 20 min. I see oil along the back of the engine and it seems to be coming from ABOVE the oil pan. I pulled an inspection plate and the bottom of the transmission bell housing is dry as is the flexplate (which would lead me to believe not a rear main seal...I thought I installed that VERY CAREFULLY). I cleaned the entire bottom of the engine with brake cleaner, put it on ramps to get a better view, and let it idle and periodically hold at 1500 rpm and 2000 rpm (total for approx 10 min). I see NO oil coming from around the pan, nothing around the oil cooler block-off plate, nothing wet in the bellhousing, but I do see some forming on the drivers side rear of the block where the 'pad' is.

So, I thought that maybe I lost a seal on the oil pressure sending unit, a leaky valley cover, or a bad valve cover gasket. I checked the VC gasket carefully and can see no signs of a leak. I tore into the intake...and there is a decent amount of oil in each runner. So much that the #5 and #7 runners actually seemed to have oil 'weeping' out of the gaskets and down the back of the valley cover. All Valley Cover bolts are tight and there seems to be no oil coming from the Valley Cover - Oil pressure sending unit connection. All intake port bolts were tightened to spec upon install. I cannot confirm if I have the newer 12570427 valve cover, as I honestly didn't know to look for it when I rebuilt the engine. It does have a brand new Melling oil pump advised for the VVT in that engine so it pumps at a slightly higher pressure than what I had when I bought the truck with 129k on the clock. When cold, it will run 40psi at idle and when driving at 1500rpm after just warming up it will hit 60psi.

I can see oil in the runners. I know I need the updated Valve Cover (The oil deflector at the pan was installed during the rebuild). However, has anyone seen oil buildup via PCV so bad that it bypassed the intake runner gasket and ran down the back of the block enough to pool and cause a substantial drip all the way down to the sway bar?

Basically my question is this: Do I keep looking for other areas where a leak may be? I'm not sure where else to look, honestly. No Service Engine lights. I need to get this resolved so I don't have the damn oil spots in my garage anymore. This is ridiculous for 4000k miles. Grrrr.....

Install the updated valve cover. The factory ones on the 2007 are the old design and will send oil straight into the intake.

 

[wsteele]

I agree that the updated valve cover is a good idea. I would also install a catch can between the PCV and the intake manifold.

A catch can is a great canary in the coal mine, will stop oil getting to the intake and a tidy way to keep an eye on how much oil your engine is pumping up through the PCV.

If it is pumping a lot of oil, it may be more than the down rev valve cover.

 

[donjetman]

MLRTYME, you have an all aluminum L92 engine(as do I). The aluminum blocks can be porous and weep oil thru the block. There is a TSB about it.

wsteel and Geotrash have given you good advice too.

Also, the more vacuum you put on the engine, the less it will weep, so that makes the updated valve cover, GM# 12570427, even more important.

 

[iamdub]

+1 to all of the above.

 

[MLRTYME]

Thanks to all the replies. I am holding off on buttoning everything up and driving again until the updated VC comes in as well as the catch can setup I ordered. That should be sometime next week. I will report back to all on the status of the oil system when that is all setup correctly.

 

[swathdiver]

Hey all,

I have a 2007 Yukon Denali (6.2L, no AFM) and I recently rebuild the engine (approx 4200 miles ago). Full rebuild w/ new pistons/rings, lifters, main/rod bearings, timing gear, oil pump, rebuilt heads...etc...etc. I recently went on a longer trip than normal and saw oil dripping from the sway bar after it sat at home for about 20 min. I see oil along the back of the engine and it seems to be coming from ABOVE the oil pan. I pulled an inspection plate and the bottom of the transmission bell housing is dry as is the flexplate (which would lead me to believe not a rear main seal...I thought I installed that VERY CAREFULLY). I cleaned the entire bottom of the engine with brake cleaner, put it on ramps to get a better view, and let it idle and periodically hold at 1500 rpm and 2000 rpm (total for approx 10 min). I see NO oil coming from around the pan, nothing around the oil cooler block-off plate, nothing wet in the bellhousing, but I do see some forming on the drivers side rear of the block where the 'pad' is.

So, I thought that maybe I lost a seal on the oil pressure sending unit, a leaky valley cover, or a bad valve cover gasket. I checked the VC gasket carefully and can see no signs of a leak. I tore into the intake...and there is a decent amount of oil in each runner. So much that the #5 and #7 runners actually seemed to have oil 'weeping' out of the gaskets and down the back of the valley cover. All Valley Cover bolts are tight and there seems to be no oil coming from the Valley Cover - Oil pressure sending unit connection. All intake port bolts were tightened to spec upon install. I cannot confirm if I have the newer 12570427 valve cover, as I honestly didn't know to look for it when I rebuilt the engine. It does have a brand new Melling oil pump advised for the VVT in that engine so it pumps at a slightly higher pressure than what I had when I bought the truck with 129k on the clock. When cold, it will run 40psi at idle and when driving at 1500rpm after just warming up it will hit 60psi.

I can see oil in the runners. I know I need the updated Valve Cover (The oil deflector at the pan was installed during the rebuild). However, has anyone seen oil buildup via PCV so bad that it bypassed the intake runner gasket and ran down the back of the block enough to pool and cause a substantial drip all the way down to the sway bar?

Basically my question is this: Do I keep looking for other areas where a leak may be? I'm not sure where else to look, honestly. No Service Engine lights. I need to get this resolved so I don't have the damn oil spots in my garage anymore. This is ridiculous for 4000k miles. Grrrr.....

What oil pump did you use? The all aluminum engines use the M365 which pumps 1/3 more oil per revolution than the iron block pumps and runs at a lower oil pressure. This is by design because of the increased tolerances of aluminum engines. Mine runs around 36 psi at speed once warmed up which is close to the bypass spring rate at 33 psi.

 

[MLRTYME]

What oil pump did you use? The all aluminum engines use the M365 which pumps 1/3 more oil per revolution than the iron block pumps and runs at a lower oil pressure. This is by design because of the increased tolerances of aluminum engines. Mine runs around 36 psi at speed once warmed up which is close to the bypass spring rate at 33 psi.

I will need to pull the oil pump data from my purchase history, as I don't have that handy. I did purchase the one Melling specifically shows as recommended for the 6.2 with VVT. However, I do have an update:

1- Pulling the valve cover showed the previous design valve cover was in place. Replacing with the newer design is something I hope will help this situation.
2- When pulling the old valve cover, I discovered the rear-most bolt was not torqued to the same spec as the other 3. Weird, as I mark each of my bolts when finished torque patterns to spec, but I can confirm it was less than 1/2 the torque needed to remove the bolt in comparison to the others. I feel confident much of my leak was being generated from there, but just in a location on the back of the head/block that I could not see before.
3- I have just under 500 miles after the VC change and proper torque of the valve cover. I do not see any of the oil drip that existed before.
4- I did install the catch can but due to other needs, I do not have 500 miles on the truck yet. At 500 miles, I will check the catch can and see how much oil has made it to the can.
5- In general, the truck seems to run more smoothly than before. Based upon the difference, I believe that oil WAS getting into the combustion chamber in larger volumes than should have been, but not enough for me to see any white smoke under use. However, pulling the catch can will provide a more definitive answer on 'how much' oil. Of course, changing Valve Cover and adding catch can does change 2 variables at once (not a good idea for scientific-method testing, but needed for my timeline) but I will report back quantity of oil in the catch can.

 

[wsteele]

I will need to pull the oil pump data from my purchase history, as I don't have that handy. I did purchase the one Melling specifically shows as recommended for the 6.2 with VVT. However, I do have an update:

1- Pulling the valve cover showed the previous design valve cover was in place. Replacing with the newer design is something I hope will help this situation.
2- When pulling the old valve cover, I discovered the rear-most bolt was not torqued to the same spec as the other 3. Weird, as I mark each of my bolts when finished torque patterns to spec, but I can confirm it was less than 1/2 the torque needed to remove the bolt in comparison to the others. I feel confident much of my leak was being generated from there, but just in a location on the back of the head/block that I could not see before.
3- I have just under 500 miles after the VC change and proper torque of the valve cover. I do not see any of the oil drip that existed before.
4- I did install the catch can but due to other needs, I do not have 500 miles on the truck yet. At 500 miles, I will check the catch can and see how much oil has made it to the can.
5- In general, the truck seems to run more smoothly than before. Based upon the difference, I believe that oil WAS getting into the combustion chamber in larger volumes than should have been, but not enough for me to see any white smoke under use. However, pulling the catch can will provide a more definitive answer on 'how much' oil. Of course, changing Valve Cover and adding catch can does change 2 variables at once (not a good idea for scientific-method testing, but needed for my timeline) but I will report back quantity of oil in the catch can.

Another thing you might check when you get time are the spark plugs for oil fouling. Since you have that new valve cover and catch can, you likely won’t be adding much to that, but cleaning any oil/carbon fouling that was created by the oil ingestion might make her run even smoother.

Start with #7, that might be the worst of them.