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Air pressure in the line? What line? I always fill a filter if it's vertical mounted and never heard any air pressure or noises or burning oil smell or anything else. It may or may not help but there's no way it can hurt. All I get is instant oil pressure and that' it.
When the oil pump first turns as you start the engine, it pushes oil through the oil line or bore or whatever you want to call the opening in the block that goes from the pump in the front to the oil filter area. This all happens in the first 1 to 1.5 seconds. That line was drained when the filter was removed. When you fill the pan and start the engine, the oil pushes (compresses) the air that's in that line until it finds an opening to atmosphere. If you pre-filled the filter, the air compresses until it pushes the oil in the filter up and into the line that contains the "barbell", which in turn compresses the air in front of that oil until that air finds a path to atmosphere in the oil gallery. Then the oil that is still in front of the second air pocket distributes itself and allows the second air pocket to be pushed out to atmosphere. Essentially, by pre-filling the filter, you create the portion of oil that was in the filter to be pushed through the system between two pockets of air. This drawing of the lubrication system may help you understand what happens.
Here's a photo of the "barbell" that resides in the horizontal portion of the line immediately following the filter exit. In the next photo you can see some of it outside of the block. The rear cover holds it in the block and you can see an outline of it on the rear cover. If the pressurized air and oil behind it squeeze past the o-ring, so will a bit of oil. Once the line is full of oil, the o-ring seals itself.
Look closely at the area about 5 o'clock from the "barbell" in this photo and you'll see the dark charred remains where a bit of oil squirted past the weak side of the gasket and the heat of the block eventually dried it. That's where the oil smell emanates from after an oil change and the shock that forces it past the o-ring. It's also why you can't locate the source and why the smell eventually goes away, yet repeats itself after the next oil change. It's also why most of the time when dealers replaced the rear seal, which required installing a new rear cover gasket, the smell went away too. At least for the next few oil changes.
^^So the only "damage" that may be caused is an internal oil leak that can cause a burning oil smell due to the filter being pre-filled? I've read on here many times about that smell and as far as I remember most of them happen after a oil change visit from the dealer. I doubt the dealer pre-fills the filter before installing it.
^^So the only "damage" that may be caused is an internal oil leak that can cause a burning oil smell due to the filter being pre-filled? I've read on here many times about that smell and as far as I remember most of them happen after a oil change visit from the dealer. I doubt the dealer pre-fills the filter before installing it.
Pre-filling the filter just doubles the likelihood of creating the oil smell problem by having two air pockets instead of one. It's more likely that the oil change kid at the dealer contributes to the creation by quickly starting the car after the oil is poured in and reving the engine higher than a normal cold start idle. Most DIY guys tend to take their time between adding oil and starting the engine and rarely do more than an idle when starting the engine.
If you look at the photos, you can see some slight discoloration where the rubber/silicone seal of the gasket was located. Google 12639249 to see a gasket. Take note that the only place that the seal is outboard of the centerline between bolt holes is the area around the "barbell". If the gasket surrounded, rather than skirted, that area, we wouldn't be having this conversation nor the oil smell. I'm guessing that GM found the problem, but chose to ignore it due to the costs involved. They may also have slightly changed the torque settings at initial assembly to reduce the possibility of leakage at that point.
BTW, this engine only had 2 oil changes in 72K miles done by someone other than me. I never noticed an oil smell, even though there is some evidence of leakage.
When the oil pump first turns as you start the engine, it pushes oil through the oil line or bore or whatever you want to call the opening in the block that goes from the pump in the front to the oil filter area. This all happens in the first 1 to 1.5 seconds. That line was drained when the filter was removed. When you fill the pan and start the engine, the oil pushes (compresses) the air that's in that line until it finds an opening to atmosphere. If you pre-filled the filter, the air compresses until it pushes the oil in the filter up and into the line that contains the "barbell", which in turn compresses the air in front of that oil until that air finds a path to atmosphere in the oil gallery. Then the oil that is still in front of the second air pocket distributes itself and allows the second air pocket to be pushed out to atmosphere. Essentially, by pre-filling the filter, you create the portion of oil that was in the filter to be pushed through the system between two pockets of air. This drawing of the lubrication system may help you understand what happens.
Here's a photo of the "barbell" that resides in the horizontal portion of the line immediately following the filter exit. In the next photo you can see some of it outside of the block. The rear cover holds it in the block and you can see an outline of it on the rear cover. If the pressurized air and oil behind it squeeze past the o-ring, so will a bit of oil. Once the line is full of oil, the o-ring seals itself.
Look closely at the area about 5 o'clock from the "barbell" in this photo and you'll see the dark charred remains where a bit of oil squirted past the weak side of the gasket and the heat of the block eventually dried it. That's where the oil smell emanates from after an oil change and the shock that forces it past the o-ring. It's also why you can't locate the source and why the smell eventually goes away, yet repeats itself after the next oil change. It's also why most of the time when dealers replaced the rear seal, which required installing a new rear cover gasket, the smell went away too. At least for the next few oil changes.
I have read about (and experienced firsthand) the "burning oil smell" in my C6 for over 5 years now, and this is the first time I have ever heard of this explanation.
I use my real name because i am a real ASE Certified Mechanic (retired)
I fill the oil filter on any car that i want to last. they will knock if you don't.
On a vertically mounted filter I get it, but what about on a angled/horizontal one ? What about a non-canister type filter, such as this ?
Pre-filling the filter just doubles the likelihood of creating the oil smell problem by having two air pockets instead of one. It's more likely that the oil change kid at the dealer contributes to the creation by quickly starting the car after the oil is poured in and reving the engine higher than a normal cold start idle. Most DIY guys tend to take their time between adding oil and starting the engine and rarely do more than an idle when starting the engine.
If you look at the photos, you can see some slight discoloration where the rubber/silicone seal of the gasket was located. Google 12639249 to see a gasket. Take note that the only place that the seal is outboard of the centerline between bolt holes is the area around the "barbell". If the gasket surrounded, rather than skirted, that area, we wouldn't be having this conversation nor the oil smell. I'm guessing that GM found the problem, but chose to ignore it due to the costs involved. They may also have slightly changed the torque settings at initial assembly to reduce the possibility of leakage at that point.
BTW, this engine only had 2 oil changes in 72K miles done by someone other than me. I never noticed an oil smell, even though there is some evidence of leakage.
Why would that cause an oil smell? I'm missing it. Isn't the oil pretty much just leaking back into the crankcase in this situation?
My swap has an oil filter relocation with 48" lines. If I turn the filter so that it faces up, the filter will drain back into the pan. So initially starting the engine it has to re-fill the oil filter every single time.
I looked around and I see a lot of similar relocations, filter facing up wards.
It bothers me that the lines empty, but as I came to the same conclusion about residual oil, I am not sure it matters if the oil lines are kept full or not. In either case, I found I could keep the oil in the filter by angling it down slightly, and it decreases the time delay for oil pressure to show on the gauge. To me that sounds like a longevity boost, isn't that the idea behind an oil accumulator? I am thinking of adding one for all around safety but also cold-start pressurizing and/or hot-turbo engine off, as the turbo engineering staff said it would increase lifespan of the turbo.
Why would that cause an oil smell? I'm missing it. Isn't the oil pretty much just leaking back into the crankcase in this situation?
Look at the dark area near the 5 o'clock position on the third photo. That's where the oil went and dried up when some leaked past the o-ring on the barbell and out the weak side of the rear cover gasket. After an oil change, the line between the pump and the upper oil gallery is drained. When the engine is restarted (particularly at a higher than normal rpm), the rush of new oil filling the void hits the barbell and is preceded by an air pocket. The initial shock can push air and some oil past the o-ring and the gasket seal. Most of that oil drips down the inside of the rear cover and into the pan, but some passes through to that dark area, which also has the capability to drip down inside of the space between the block and the bellhousing. It's in that space where the oil is exposed to atmosphere and the heat of the block to evaporate, creating the smell, and eventually dry up.
Well he may have a point about the air pockets and hammering the barbell,
but I would still fill the filter, despite the increased tendency to spill a bit of oil,
both because
A: They sell a better barbell for these engines which will eliminate this issue I believe
and
B: Reduced time to see oil pressure on the gauge is still worth every second (think of an oil accumulator)
I haven't had the pleasure of an oil change in my Vette' yet but I've been doing my oil changes on my 7.3L Powerstroke (Diesel) which holds near 16 quarts for almost 20 years. I always pre-fill that filter which holds about a quart all by itself. When I'm done and I start that engine it still takes a few seconds for the gauge to register and the engine get to sounding normal again. I would hate to see how long it would take if I didn't pre-fill the filter.
My Harley on the other hand has a horizontal filter mount so there's no pre-filling that one. When I fire that up after an oil change it is pretty dramatic in the sound change once the flow of oil is back to normal. It sure seems more engine wear occurs at this stage of engine life than any other.
My Harley on the other hand has a horizontal filter mount so there's no pre-filling that one. When I fire that up after an oil change it is pretty dramatic in the sound change once the flow of oil is back to normal. It sure seems more engine wear occurs at this stage of engine life than any other.
Actually a tip: you can about half-way fill the filter and let the paper inside it absorb the oil. It will keep that portion inside the filter while it is sideways
Residual oil is supposedly what keeps the bottom end happy when there is no oil pressure. The noise may be the lifters/valvetrain related and completely harmless to listen to at idle.
Still makes you cringe though, right? I know I do.
Its one of those questions with so many variables. When I first started looking at LS motors I was compression testing them. And when I do that I fill the engine with oil first.
Turns out, within the time frame of compression testing, there was no oil pressure in those engines I was testing, even with oil in the pan it wasn't cranking long enough during the compression test to even begin to fill the filter. It actually takes a good 30 seconds of cranking on a dry engine to see oil pressure beyond the filter in my experience after checking approx 11 different junkyard engines. Makes you really think, all the time I was assembling my motor, testing it, turning it over to move the rocker positions to put the head on it, turning it over to clean the bores/pistons, all the time I spend cranking it after that, 30~seconds+ , it didn't have a single psi of oil pressure.
And now it runs fine like nothing out of the ordinary happened. Hmf.
HOXXOH, is your statement on ALL cars, or just this engine? I pre-fill all my cars...Your point is very interesting...
If you mean the oil smell after an oil change, it applies to LS engines. I'm not familiar with all the oil flow direction and passages on other engines, so can't comment on those. One thing is for sure, that you can't pre-fill filters with bottom entrance/exits and those cars don't have problems, even if the filter drains itself everytime the engine is shut off.
If you are referring to the residual oil film that remains after draining at an oil change, then at idle speed, you can run a solid lifter engine easily for 2-3 minutes with no oil flow or a hydraulic lifter engine for well over a minute with zero oil flow and not incur damage. I've witnessed both occasions and seen the subsequent engine teardown to identify damage and saw nothing that required replacement of any parts. I've also seen overfills (forgetting to drain oil before adding new oil), however those did damage seals and some caused a seizure. If you did that to a LS7 (extra 9 to 11 quarts) it was a guaranteed dead engine. Even the Cash for Clunkers program drained the oil, added 2 quarts of a liquid glass solution (40% sodium silicate, 60% water) and ran the engine at a high speed and the engines lasted for up to 5 minutes before seizing.
03-18-2018, 11:36 PM
