Oil leak from Oil Pan and Oil Pressure Relief Valve

[rdezs]

There's a TSB regarding the porosity issue on the aluminum blocks. The issue is on the back of the engine in areas not covered by the rear cover. The fix for it according to GM is to spear some RTV across the back of the block. I've never actually ran across one but I'd be pissed.... I view that as a defective block.

There is no oil pressure on the passenger side of the block. Crankcase pressure would be the only thing pushing oil outward past a week seal, gasket or o ring. The volume of oil in the video coming down on the passenger side with almost have to be pressurized by crankcase pressure. Unless of course there's a quarter inch of valve cover gasket missing.

 

[05gto]

Sometimes you have to step back and think outside the box. Your oil pan gasket is fine. When you did the AFM delete, you had to remove the dipstick on the passenger side to deal with the exhaust manifold. To me, based on where the oils dropping down, it looks like the dipstick is not seated all the way in the block. (And if it has another half inch to go, the crankcase is quite overfilled)

I've seen cases where people have completely missed the dipstick tube opening in the block when trying to reinstall it. Also if the o-ring on the tube is completely trashed. And then there's been several cases where the lower part of the dipstick tube is completely rusted through.

Based on the amount of pressure pushing oil out, it's quite possible it's aggravated by a plugged PCV system. Verify you have vacuum in the crankcase at idle. (At idle, if you just lift the dipstick up your idle should change a little, due to the vacuum leak you just created.) You can easily adapt a hose to fit a common vacuum gauge and connect it on the passenger side valve cover which is the fresh air intake. After about 10 seconds you should start to see a slow increase in vacuum. If the PCV system is plugged or even partially plugged, that will pressurize your crankcase and the pressure will blow out the weakest seal. (I replace that o-ring on the dipstick anytime I have it out)

Well that's my two cents worth..... I could be wrong, but I don't think so

I have to check this Sunday when I get to work on it again. Thank you

 

[05gto]

Does the problem also occur when the engine is warmed up and the oil pressure has tapered down a bit with the warmer oil?

The oil pressure relief valve in the pan is a pop-off valve. It's spring loaded and is supposed to pop open when the AFM system changes modes with the pressure spikes, and then pops back closed. If you removed it and the AFM system, there really is no reason for it. Your oil pump pressure spring is what governs the output pressure from the pump. Melling HP pumps ship with 3 different springs so you can choose a lower pressure spring if you want to. But that said, I see no problem with the oil pressures you mentioned. My 2012 has a Melling high pressure oil pump in it using the spring that shipped installed in it, and I see similar pressures to yours across the range. Mine still has the pop-off valve in the oil pan, but I doubt it's even opening because there are no pressure spikes from the AFM system any more since I deleted the whole thing. I did replace that pop-off valve with a new one, but I still don't see any issues with your pressures.

So, my money is on the crank position sensor o-ring above/behind the starter. And as rdezs says, it's being aggravated by a plugged PCV system.

The only other thing I can think of that hasn't been mentioned yet is that the 6.2L blocks have occasionally had porous casting issues. When that happens, oil can leak right through the aluminum. But I've only read of it in articles, and have never seen anyone here having that problem.

I never had any oil leaking problems before the rebuild song doubting, at least hopefully that it's not a casing issue. I'll try and check the other suggestions later this week when I'm able to work on it again. Thank you for the insight

 

[Geotrash]

I never had any oil leaking problems before the rebuild song doubting, at least hopefully that it's not a casing issue. I'll try and check the other suggestions later this week when I'm able to work on it again. Thank you for the insight

Unless the previous owner had the TSB service done per GM specs. That wouldn’t survive a rebuild unless the block was never cleaned.

But I see that as a long shot anyway. Something is up with your PCV system (or you have a hole in a piston). The crankcase pressure is likely the problem, not the oil pressure.

 

[rdezs]

When installing the dipstick tube, that flange has to be down against the block all the way. If it's up 1/8 of an inch, the o-ring probably never got pressed into the hole in the block. If it doesn't take a bit of force to get it in, your old o-ring is worn out. I put the open end of a small crescent wrench around the tube and on top of the flange, then with a pry bar.... Take advantage of the angle on the end.... Lightly tap it down the rest of the way with a small hammer.

I've seen the heat from the exhaust manifold take its toll on more than a few dipstick tubes. You'll notice you get rust with the heat has cooked off the paint. I've seen holes in the lower part of the dipstick tube from that corrosion. New genuine GM dipstick tubes complete with the o-ring are about $25.... Well worth replacing anytime you pull it out.

 

[05gto]

Unless the previous owner had the TSB service done per GM specs. That wouldn’t survive a rebuild unless the block was never cleaned.

But I see that as a long shot anyway. Something is up with your PCV system (or you have a hole in a piston). The crankcase pressure is likely the problem, not the oil pressure.

I agree with suggestions now on pcv. This makes sense. Looking forward to testing.

 

[Dustin Jackson]

With that amount of oil it should be easy to see where its coming from. Going bottom to top there is the oil pan gasket, I think there is a plug in the side of the block for an optional knock sensor or oil (this might be under the exhaust manifold making it hard to see), might be an oil level sensor, you have your head gaskets, then your valve cover gaskets, valley cover gaskets, oil pressure sensor, PCV is up there also.

It sounds like you know a bit so I'm sure you covered most of that, I am super curious about this one.

 

[rdezs]

The video shows the passenger side of the engine is the source. Both the crankshaft position sensor and the dipstick tube where it enters the block are difficult to see with the starter installed. And that's all there is on the passenger side of the engine besides the head gasket and valve cover gasket. Nothing on that side of the engine has oil pressure.... Which is what led me to his engine having excess crankcase pressure, commonly from a plugged PCV orifice in the driver side valve cover. (Or even a hole in the piston as Geotrash suggested)

All of the oil pressure is on the driver side of the engine block, and up to the sending unit at the top rear driver side. (And with AFM, also through the valley cover plate....the 'VLOM')

As a side note, the bolts securing the valley plate or the VLOM, are commonly found to be loose. Leaks from here usually go down the back of the engine, dripping at the rear of the block on both sides. Much more of a problem with the AFM engines.

 

[Geotrash]

The video shows the passenger side of the engine is the source. Both the crankshaft position sensor and the dipstick tube where it enters the block are difficult to see with the starter installed. And that's all there is on the passenger side of the engine besides the head gasket and valve cover gasket. Nothing on that side of the engine has oil pressure.... Which is what led me to his engine having excess crankcase pressure, commonly from a plugged PCV orifice in the driver side valve cover. (Or even a hole in the piston as Geotrash suggested)

All of the oil pressure is on the driver side of the engine block, and up to the sending unit at the top rear driver side. (And with AFM, also through the valley cover plate....the 'VLOM')

As a side note, the bolts securing the valley plate or the VLOM, are commonly found to be loose. Leaks from here usually go down the back of the engine, dripping at the rear of the block on both sides. Much more of a problem with the AFM engines.

Spot on. All of it.

The valley cover bolts on my L94 were barely finger tight after 9 years and 120K miles back in 2021, but it wasn't leaking. For the benefit of others - the gasket under that plate takes a set after a while, gradually releasing the tension from the bolts. If there is any crankcase pressure at all, that gasket will start leaking big time.

 

[rdezs]

Lol, I'll bet you had four to six of them less than finger tight. Sounds crazy, but completely typical.

 

[West 1]

It is not a pressure problem caused by the oil pump. You have a leak. I just re watched this on a 21" screen. Your leak starts dripping at several oil pan bolts on both sides of the oil pan? This tells me the oil pan gasket is not sealing the pan to the block at all. I bet you could slip a feeler gauge maybe .020 thick along the top of the gasket and slip it into the block. Nothing else will leak on both sides of your block. With the engine running there is oil throw off at the connecting rods in normal operation. This oil splash is the pistons only oil supply. If the pan is not sealed this same splash can get out of the engine past the pan gasket along with all other oil draining back down from the top of the engine.

Any chance the oil pan bolts are bottoming out in the block before the gasket is clamped tight? You could remove the bolts one at a time and use high pressure air and maybe a wire to probe up there and make sure some old gasket or dirt is not jammed in the bottom of those oil pan bolt holes.

Second mechanical issue to rule out. The Oil pan gasket has torque limiting sleeves at each bolt hole. IF by chance those sleeves are the wrong height the gasket can't crush into place and seal. With all the low priced pan gaskets out there you might find the wrong sized torque limiters in your gasket. In that case all bolts torque properly but the gasket has never been crushed into place allowing leaks all around the oil pan.

If you torqued the Tranny to the oil pan using those big bolts first the oil pan would not be able to move up into place as designed and will leak or the pan will break.

You have to bring the oil pan up to snug by hand with all the oil pan bolts first then get your 2 large tranny bolts in and screw them down till almost snug. At this point I loosen all the oil pan small bolts maybe one full turn. This will allow the oil pan to slide back as the tranny to oil pan 2 large blots are tightened to pull the pan back to its needed position. Now loosen the 2 large tranny to oil pan bolts maybe one full turn but no more. This will let the oil pan properly slide up while properly positioned to the rear. Now you have it pulled it back where it needs to be against the tranny.

At this point you have the pan positioned to the rear, back against the tranny as needed. Now slowly torque by proper sequence the 10mm Pan bolts till all are fully torqued with a torque wrench in 3 steps. The short 10mm bolts torque to 18 ft pounds or 216 inch pounds. The long 2 bolts at the rear tighten to 106 inch pounds. Torque all these and the pan is now up and torqued. Lastly, torque the tranny to oil pan 2 large bolts to 44 ft pounds ( verify this spec I may be off on these 2 bolts ) knowing you have the pan up and torqued and also back in proper position.

It is all about the sequence and evenly bringing that pan up and back into proper position before final torquing the bolts. A lot of oil pans are broken by guys not following the steps.

It takes maybe an extra 20 minutes but you can do it this way or fail. With all the new style battery powered impact wrenches you can exceed 216 inch pounds in one short burp and things go very wrong.

So far I have always used the Fel Pro oil pan gasket for these LS engines. Have not had one leak from the oil pan gasket yet and have not cracked one oil pan yet.

GM sells many of these oil pans because guys don't take the time to learn the proper install procedure.

Maybe I am super careful knowing these pans are touchy but I do final torque in 3 steps to keep from tweaking the aluminum oil pan and breaking it. If final toque is 216 inch pounds, for the short 10mm bolts I would do a first pass at maybe 55 inch pounds following proper torque sequence jumping all around the pan as all bolts are brought down to 55 inch pounds, then I would repeat at 100 or so. Final pass at 216 and the 10 mm bolts are good. The very long 10 mm bolts have a little different torque spec, these two long bolts at the rear are only 106 inch pounds torque and I bring these to final torque only after all the short 10mm bolts are all at 216 inch pounds.

To finish I torque the large 15mm tranny to oil pan bolts last and it is done, 44 ft pounds?. If your eyes can see any gap between the tranny and the oil pan before doing this final torque that would be a problem that can break the pan. The pan should have slipped back into proper position tight against the tranny prior to this step if it not in proper postion loosen all pan bolts and re position again. No choice. This step should never happen but if it does start over.

Somewhere in this note I think you will find what went wrong on your install. Hope it helps.

 

[j91z28d1]

I think he did say he used a replacement oil pan, maybe the bolts that come with it are to long?


someone could could have used rtv on the bolts last time, and the blind holes are full of it? used to happen on old manual transmission top plates a lot. you'd have to dig it out or you couldn't tighten the bolts.

 

[West 1]

Earlier Mr. O you had asked about the Oil Relief valve inside the oil pan, this was added by GM to protect AFM systems. You removed the AFM so you do not need that relief valve any longer. If I rebuild with the AFM intact I install a new pressure relief valve in the pan. If it is a non AFM engine I plug that relief hole as it is no longer needed. I think they limit oil pressure to 58 psi? This is to avoid damaging the AFM lifters.

 

[lspann3525]

I had an oil leak similar one time it turned out the old oil pan gasket came apart and the oil filter part of the gasket was stuck to the engine block and I reinstalled a gasket over it and didnt realize it.

Took the truck on a test drive to the store soon as I make it to the parking lot I could smell oil burning. So I get out and take a dive underneath the truck and it was raining oil similar to yours.

I felt really dumb but it was my fault for not having adequate lighting and I was rushing then messing around with the front diff and rack n pinion. almost was like a nightmare

 

[charkmapman]

There is crank bearing position bolt above starter. It is known to loosen. It will leak oil like crazy. remove starter, remove bolt, clean bolt threads and block threads with brake cleaner, apply aviation form a gasket to threads, reinstall, torque to spec.

 

[Sagmanovich183]

Sometimes you have to step back and think outside the box. Your oil pan gasket is fine. When you did the AFM delete, you had to remove the dipstick on the passenger side to deal with the exhaust manifold. To me, based on where the oils dropping down, it looks like the dipstick is not seated all the way in the block. (And if it has another half inch to go, the crankcase is quite overfilled)

I've seen cases where people have completely missed the dipstick tube opening in the block when trying to reinstall it. Also if the o-ring on the tube is completely trashed. And then there's been several cases where the lower part of the dipstick tube is completely rusted through.

Based on the amount of pressure pushing oil out, it's quite possible it's aggravated by a plugged PCV system. Verify you have vacuum in the crankcase at idle. (At idle, if you just lift the dipstick up your idle should change a little, due to the vacuum leak you just created.) You can easily adapt a hose to fit a common vacuum gauge and connect it on the passenger side valve cover which is the fresh air intake. After about 10 seconds you should start to see a slow increase in vacuum. If the PCV system is plugged or even partially plugged, that will pressurize your crankcase and the pressure will blow out the weakest seal. (I replace that o-ring on the dipstick anytime I have it out)

Well that's my two cents worth..... I could be wrong, but I don't think so

Thanks again Rdesz and other here who responded to my post early this week! And per Rdesz above I'm taking a break and thinking and listening to seasoned advice before doing...

I posed actual photos of my old pan gasket that I was sure was my oil leak problem... and I just replaced and is still leaking (drop per second down passenger side seam after a 40 minute drive).. more on this by tomorrow as I rip passenger side skirt and tire off for a better view) but between starter mount and just to the passenger side of bell housing observation port. drip drip drip...

Having a fluid mechanics/pressure transducer mfg background i'm seeing oil passages, orings and seals in my sleep and comments about the metered valve cover and PVC vacuum is bugging me and as I was once reminded - ' a chain is only as strong as its weakest link ' and i wonder if my crankcase is building pressure.

To date I spliced a clear 3/8" tube between valve cove/intake vent tube and brough her up to temp and idle vacuum squished it no problem and I can blow through either way with similar long piece from my mouth easy into intake harder through meters valve cover port)

So despite my replacing the valve cover to intake vent line which had a lose seal at v-cover maybe new pan gasket ahas popped at the passenger side parting line of oil pan and main seal cover? I plan to zoom in on this today...

So I may try and dig up a vacuum gage and test if there is a partially blocked meter hole in valve cover but also maybe it's time to also upgrade the driver side to the metered valve cover? Understanding the fresh air intake mentioned that is the passenger side valve cover is on my todo today as well. With oil fill cover off my engine draws a clear plastic swatch reasonably tight so ther is some vacuum but again maybe not enough?

I will likely remove and inspect starter side of engine block/oil pan/bell-housing interface next ( and position sensor - which isn't under pressure so i can't see that generating a one drop per sec drip) and beside v-cover and exhaust oil pressure sensor and valley pan ( is there pressure here? idk )

All this before going back to oil pan (if PVC system turns out to be weak) and as last course RMS.

Labor day weekend so why not labor away I guess

Any feedback is appreciated.

 

[rdezs]

Keep in mind oil once it leaks out, travels not only downward but horizontally depending on the air flow in the engine compartment. One drop per second is significant.

With the passenger side inner fender well removed, engine running, try to get a good look at the dipstick tube where it goes in the block. (Also feel the tube itself for any holes rested through on the back side) you'll probably need to pull the starter to get a good look at the crankshaft position sensor.

Did you reach back behind the intake, and feel just below the valley cover plate all the way across for any oil? The oil pressure sending unit is back there too, and they're known to leak when they go bad.

The rear main is a possibility.... Most of the oil gets flung to the passenger side from the direction the flex plate spins. Of course, you want to make damn sure you checked the other possibilities 100% before diving into that.

Something I would do right off is hook a vacuum gauge up to your PCV fresh air hose on the passenger side valve cover. You can do this with a t connection, or simply unhook it for test purposes and hook up the vacuum gauge. Then start the engine. In about 15 seconds you should start to see a vacuum build. If the gauge goes the other way and starts building pressure, you know your PCV orifice in the valve cover on the driver side is probably plugged. Or.... Worst case scenario is you have so much blow by from broken rings or worn valve guides, that your PVC system can't keep up with it. But I would assume you'd have other symptoms regarding drivability if that was the case. If it does slowly build vacuum, then you definitely have a pressure leak. (Oil pressure sending unit at the back of the engine, and if it's an AFM engine.... It actually screws into the VLOM cover plate, which has a gasket between it and the block.... Which is where it could be leaking. And if that's all dry, and you're not building crankcase pressure, but unfortunately you're probably looking at the rear engine cover or rear main seal.

 

[solli5pack]

My armchair QB guess is that the rear main housing is the leak.

 

[Joseph Garcia]

I'm having an issue where oil is leaking badly from oil pan during load. Have a 6.2L 2012 yukon that has been rebuilt with dod/afm delete as well as vvt delete. Bought Part# 12710304 Oil Pump directly from GM. Getting close to 70 psi oil pressure idle on cold start. Around 40 when warm. Under load of drive it leaks and drops to around 22 psi. My thought is pressure is too high causing the leak (video link below showing leak) . Oil pan gasket has been replaced twice, and oil pan replaced once.

***Question: will putting a oil pressure in oil valve back in oil pan help relieve pressure, or is this valve only activated by dod/afm? Will I have to buy a smaller oil pump?

Lots of good content in this thread. I can tell you for with absolute certainty that your issue is not related to the oil pressure relief valve, installed or not installed. Leave that delete plug installed and follow the advice of others in finding the source of your leak.

 

[alvocado]

There was an earlier suggestion to use some UV oil dye. I would clean everything up, add dye and see if that helps pinpoint the source. It’s been helpful for me on a leak that I thought was from an oil pan but ended up being a rear main.