I have a 97 Sentra with a GA16DE. Losing oil BAD. Definitely has slow front seal leak that I will take care of but not bad enough to cause this much of a leak. Pulled plugs and #4 came out soaked with oil. Looked in plug hole and saw oil sitting on piston. Cranked without plugs in to clear out and watched in same hole. Was no oil on piston and slowly watched oil cover it from LF of car toward RR of car.
I know there are sever possibilities But I'm wondering which one you would think is the cause? Would a spark plug tube seal cause this kind of leak?
Would it be a valve seal? Would this "rectangular gasket" everyone keeps talking about cause this? Which one would most likely be the culprit?
If plug tube seals: will the tubes pull out with cover off?
If Valve seals is there an easy guide for replacement? What needs to be removed to pull cams?
I would lean towards bad valve stem seals. However run a compression test on the engine to see the condition of the rings.
To remove the cams, the upper chain needs to be removed. First set the #1 cylinder to TDC on the compression stroke and mark the timing chains so that you can correctly re-time the chain assembly.
What needs to be removed to pull the cams?
For one thing, the Haynes and/or Chilton's manual will tell you that.
Distributor out, Valve cover off, timing cover off (maybe), chains off the sprockets (easier with the timing cover off, might not be possible with it on), loosen the cam bearings in the order specified by the book (otherwise you'll bend the cams), lift the cams off the lifters. Lift the lifter buckets off the valves using a magnet. Keep them in the same order you took them off. Again, if you're lucky and have the right tools, you might be able to get a valve compressor in there, remove the keepers, springs, and old valve seals and put new ones on.
But it tells you all of this in the book...
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99% of the questions that are "STRANGE" have a dirt simple answer...usually answered by a dirt simple search.
Is it just me, or does the majority overlook the obvious?
Somebody ate a whole bag of dumbass for breakfast.
Why do people continue to run a vehicle when a warning light comes on or starts flashing? Isn't that a clue that something is wrong and you probably should NOT drive it?
Is this whole car driving thing really freekin' brain surgery?
Here's something new for the crowd/clowns...
"A little bit of Google goes a long way!"
Ever notice the one post wonders for info on turbo'ing a GA16 are never heard from again after they figure out the cost???
And if you can read this, you don't need glasses! :)
What needs to be removed to pull the cams?
For one thing, the Haynes and/or Chilton's manual will tell you that.
Distributor out, Valve cover off, timing cover off (maybe), chains off the sprockets (easier with the timing cover off, might not be possible with it on), loosen the cam bearings in the order specified by the book (otherwise you'll bend the cams), lift the cams off the lifters. Lift the lifter buckets off the valves using a magnet. Keep them in the same order you took them off. Again, if you're lucky and have the right tools, you might be able to get a valve compressor in there, remove the keepers, springs, and old valve seals and put new ones on.
But it tells you all of this in the book...
I would lean towards bad valve stem seals. However run a compression test on the engine to see the condition of the rings.
To remove the cams, the upper chain needs to be removed. First set the #1 cylinder to TDC on the compression stroke and mark the timing chains so that you can correctly re-time the chain assembly.
I was leaning toward the valve seal myself as I can't imaging how a ring could allow the oil to leak up to cover the piston again while just sitting there. However, I wasn't aware of that much oil sitting over the valve seal to leak into the cyclinder like that. I guess I haven't looked closely at the design of the head in that area though. I also have not removed one of these valve covers yet to be familiar with the exact design of the plug tubes to know if there was a way for oil to leak past the seals into the cylinder that was behind the visible inside diamter of the tube wall. If so that may be possible as well. I'm just trying to troubleshoot the best I can prior to tear down to help with anticipating what extent of repair will be needed upon tear down. However, it looks as if I'll just have to plan to pull the v.c. first.
As for removing the cams the manuals I have, specifically from here: Nissan Service Manuals | Full Nissan Service Manuals & Free Loose Sections - Nissanhelp.com, fail to show how to remove only the cams without going into what I would call basically full top end and both timing chain R&I. I wasn't sure if Haynes or Chilton's would be any better about it as even my Alldata sometimes shows nothing more helpful.
I figured I would probably have to remove the distributor and pull the upper chain off the cam sprockets but didn't know if I could just do that by removing the upper front cover and chain tensionser, which may need replaced while I'm in there. Would that give me enough slack to pull the chain without removing the bottom front cover?
Also, If I have to set it at #1 TDC to keep it inline for simple retiming then I'm assuming I'll need to have an air pressure adapter fitting to supply pressure through the plug hole to avoid dropping the valves that I'm working on. Is this correct or is there another way to do this without pulling the head?
Another possibility would be a bad head gasket, blown between and oil channel and the cylinder bore.
Yeah that thought crossed my mind as well and I was trying to avoid saying it in hopes of not having to worry about it.
I guess If I have it torn down far enough to pull cams then it's just a matter of draining the coolant, disconnecting a few more hoses and pulling the intake and ex manifold right? lol
If spark plug tube seals failed, it would cause oil to leak into the spark plug tube and pool on top of the spark plug, but it wouldn't leak into the combustion chamber (at least not until you removed the spark plug and the oil drained into the combustion chamber).
I figured I would probably have to remove the distributor and pull the upper chain off the cam sprockets but didn't know if I could just do that by removing the upper front cover and chain tensionser, which may need replaced while I'm in there. Would that give me enough slack to pull the chain without removing the bottom front cover?
Don't count on it. You might be able to wiggle the gear off the cam if you're good enough at that sort of thing. Keep the chain wired up so it doesn't fall down in there. If you get it off without pulling the cover, great. If not, gotta pull it anyways.
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Also, If I have to set it at #1 TDC to keep it inline for simple retiming then I'm assuming I'll need to have an air pressure adapter fitting to supply pressure through the plug hole to avoid dropping the valves that I'm working on. Is this correct or is there another way to do this without pulling the head?
Nope, pretty much hit the nail right there. Problem with doing that is there's a chance that the pistons will want to blow down when you apply the air pressure. If you've got a manual, not much of a problem, leave it in 5th gear and have somebody keep a foot on the brakes. Automatic...likely a problem unless you immobilize the crank somehow.
__________________
99% of the questions that are "STRANGE" have a dirt simple answer...usually answered by a dirt simple search.
Is it just me, or does the majority overlook the obvious?
Somebody ate a whole bag of dumbass for breakfast.
Why do people continue to run a vehicle when a warning light comes on or starts flashing? Isn't that a clue that something is wrong and you probably should NOT drive it?
Is this whole car driving thing really freekin' brain surgery?
Here's something new for the crowd/clowns...
"A little bit of Google goes a long way!"
Ever notice the one post wonders for info on turbo'ing a GA16 are never heard from again after they figure out the cost???
And if you can read this, you don't need glasses! :)
Nope, pretty much hit the nail right there. Problem with doing that is there's a chance that the pistons will want to blow down when you apply the air pressure. If you've got a manual, not much of a problem, leave it in 5th gear and have somebody keep a foot on the brakes. Automatic...likely a problem unless you immobilize the crank somehow
I've read somewhere that you should use like 71psi to keep the valves up. So, I'd guess that would prevent the system from rotating. Problem is I can't remember where I read that to double check and verify the reputability of that source. From what I'm looking at in the manual is if I remove the cylinder head front cover, not the block front cover I should have access to the idler sprocket bolt which should hold the bottom end in place with a wrench if I use air pressure.
As for the tubes they press into the head and the common seal leaks are at the v.c. right? Are they such a tight fit at the bottom of the tubes that they don't leak there? This is one thing I can't see clearly in the manuals and wish I could find some better pics of the tubes with the v.c. removed and some of the tubes removed if they can be pulled.
The metal spark plug tubes are pressed into the heads. Even if they leaked at the bottom, which I've yet to see, it still wouldn't cause oil to enter into the combustion chamber. Here's a pic of the cylinder head:
Thanks for the schematics. Kinda confirms the unlikeliness of the problem being a result of the tubes. Guess all roads lead to pulling the v.c. and looking at the seals.
A thought I just had is that a leak down test or possibly compression test should show a lower reading in that cylinder if the head gasket was leaking oil right? But, I just don't think that would allow it to slowly cover the piston just from oil running back down to the pan. Don't think that much oil sits anywhere in those passages to allow it to just flow into the cylinder like that when it's not running.
Thanks for all the help guys.
On a side note I wonder why they still call it a lifter when it doesn't lift. Shouldn't it be called a pusher?
If I have to set it at #1 TDC to keep it inline for simple retiming then I'm assuming I'll need to have an air pressure adapter fitting to supply pressure through the plug hole to avoid dropping the valves that I'm working on. Is this correct or is there another way to do this without pulling the head?
Like I mentioned in a previous post, The purpose of setting the #1 cylinder to TDC on the compression stroke and MARK the timing chains is that you can correctly re-time the chain assembly upon reassembly.
Once you have both cams removed and the spark plugs removed, to do the seals on a cylinder, just turn the crankshaft until the piston is at TDC; look down the spark plug hole. When the valve springs are removed, the valves will not drop into the cylinder because the piston is at TDC. No air is needed, simple! When the next cylinder is to be worked on, turn the crankshaft until that piston is at TDC.
The valves won't fall down very far, but I don't know how far they WILL fall down in there with the piston at TDC.
Might be too far to grab the valve stem tip with anything, although I would think it would be possible to grab the valve stem tip with a magnetic parts retriever type tool if the valve stem fell down into the valve guide. Even then, with a higher mileage engine, the tip of the valve stem will likely be mushroomed just a little bit, likely enough to keep it from falling into the guide at all.
__________________
99% of the questions that are "STRANGE" have a dirt simple answer...usually answered by a dirt simple search.
Is it just me, or does the majority overlook the obvious?
Somebody ate a whole bag of dumbass for breakfast.
Why do people continue to run a vehicle when a warning light comes on or starts flashing? Isn't that a clue that something is wrong and you probably should NOT drive it?
Is this whole car driving thing really freekin' brain surgery?
Here's something new for the crowd/clowns...
"A little bit of Google goes a long way!"
Ever notice the one post wonders for info on turbo'ing a GA16 are never heard from again after they figure out the cost???
And if you can read this, you don't need glasses! :)
Like I mentioned in a previous post, The purpose of setting the #1 cylinder to TDC on the compression stroke and MARK the timing chains is that you can correctly re-time the chain assembly upon reassembly.
Once you have both cams removed and the spark plugs removed, to do the seals on a cylinder, just turn the crankshaft until the piston is at TDC; look down the spark plug hole. When the valve springs are removed, the valves will not drop into the cylinder because the piston is at TDC. No air is needed, simple! When the next cylinder is to be worked on, turn the crankshaft until that piston is at TDC.
If I'm correct in my thinking on this it doesn't matter prior to putting the cams back in if the piston is on what used to be the compression stroke TDC or exhaust stroke TDC because it's the cam position in relation to the piston at TDC that determines compression vs exhaust. Right?
I was thinking about the valve quides as well but technically if the seal is leaking oil I would think it would provide extra lubrication to the guide preventing wear right?
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