At the ends of the intake cam shafts there is a valve that the vvt solenoid pushes that keeps the oil in the cam until the vvt gears move position at high revs when the solenoid retracts and allows the oil out the end of the cam. The oil gets into the cams via the holes in the cam bearing followers.
Yes it would be covered in metal shavings possibly even small peices of metal. No scale of 1-10 a spun bearing is engine out and rebuild or replace, don't ask me how I know this! The only way for it to get worse is for the engine to be started and run with a spun bearing causing even further damage to the crank beyond all possibility of salvage for a rebuild.
Ok, so a "spun bearing" is an event that happens all at once? See my noise started only at high revs and then over a few 100 km's got worse to it current point where there is no knock at idle, but progressively gets worse with acceleration. Is this not what I would expect from a bearing??
Marcus, have you tried isolating each cylinder in turn, so as to identify which cylinder is producing this knock? I apologize if you have already done this(as I have not read ALL of the history of your problem). If the knock goes away when no ignition takes place in the respective cylinder, that would pretty much point to big or little end failure as the most probable culprit. Hope this is of some help as this kind of fault finding is akin to bashing your head with a hammer, it feels sooo good when you stop.:zlove:
Try what Lloyd said - haven't heard of it before but sounds like it will work as the knock is caused by the compression/combustion of the cylinder with the culprit bearing (i think). Yes the bearings have 'tangs' which are essential a small raised edge which holds it in place - when the clearance are incorrect/lack of oil supply the bearing will bite onto the crack, tang will break and will result in a spun bearing. As the bearing further wears away while it's spinning around there is less bearing material and the knock will get worse. When I had a spun bearing in neutral under revs there was a slight knock/rattle. Under load/accelaration it was eaxctly like knocking on a table or benchtop. Drop your oil and let us know what's on the magnetic plug.
No I haven't tried that!! Thanks Chili I'll be sure to give it a go when she's back in one piece. I'm really just looking for that type of confirmation before I move to transplant surgery.
IT should never drop to zero even at idle. Like it appears Briz's engine does. Hope he isn't using the stock gauge to judge. 70psi at high revs is a good spot to be. its not easily changed. You have to get a stronger spring for the oil pump.
Could this be it?? I pulled the value covers off again today and (as per Graham's suggestion) tried to push down each of the value lifters. To my surprise one of them moved!! It sinks down 2-3mm when I lean on it hard (the others don't). It's one of the exhaust valves on cylinder 2 which corresponds nicely with estimation of where the noise was coming from (front passenger side). So now it looks like my next step will be to remove the cams and try to replace that sucker. This will require a special tool right?? Anyone done this job....easy / hard??
Easy as just get a magnet onto the lifter and it will lift straight out, just for your info I recently replaced all of my lifters with brand new ones and still had lifter tick, mainly due to the cams I was running, fixed by shimming the lifters. had another listen to your Vid, still think as I stated before that its a big end rattle.
Could be both I suppose...hope it's just a lifter . I also removed the magnetic sump plug and had a look. There was nothing significant to see. There did seem to be a fine sludge (if I could describe it that way) on the magnet. I wiped it onto a white rag and had a close look under light and there was a few very fine "sparkles" in there. They were too small to feel by rubbing between the fingers but big enough to see when reflecting light. Any thoughts on that?
Could be it Marcus - hopefully! they shouldn't really compress at all when pushing down on them by hand. Timing belt off job and cam out - those caps that actually hold the cam in - mark them so each one goes in exactly from the spot it comes out and in the same direction (cant have them turned around). CRUCIAL! Get it wrong and you can kiss your motor goodbye for sure! Hopefully not a bottom end bearing.
Those very fine sparkly bits are normal wear. If your bottom end bearing had let go to the point of hearing a knock the magnetic sump plug would have a beard of metal filings. Next question: What oil filter are you running ? If you have one of those "you bute" cartridge super fine filters remove it a peg it at the nearest tree. Those things work well if you are running a high pressure oil pump. A standard oil pump does not have enough pressure to get the oil through the cartridge filter material and the crank WILL stave of oil at higher revs and rip a big end bearing apart. What grade of oil are you running, and how old is the motor?
Newly reconditioned motor Graham. Mineral running in oil changed at 1000km. Mineral running in oil up to 2500km and then changed to Royal Purple 10w-40. Knocking started the day after that change. Oil filter changed with oil each time (just stock Nissan filter). Can't wait to get that lifter replaced now....I have a warm fuzzy feeling that we might have found the problem
As much as Im crossing my fingers, and at the risk of pouring cold water on the warm fuzzy feeling, lifter rattling is pretty much unrelated to engine LOAD. It will happen all the time if it happens at all. Given that leaking within the lifters would be the culprit and the leaking against time is a constant, then the issue will become less and less as rpm rises as the valve event shortens in time as revs rise. Gives less time for the lifter to leak away see? That noise is related to load and accelleration pure and simple. The vid clip quite clearly demonstrates this. The engine is quiet as a mouse at all other times which points to something accessory related. Even with the dodgey recording, the noise sounds quite external to me. Have you tried running it sans all accessory drive belts just to rule anything out like that? Does the noise ever reduce at anytime when driving? Like no change when clutching? Rule out loose flywheel bolts. Your positive the cam belt tensioner and idler bearings are tight and noise free? Matters not if they were brand new either. Same goes for the tensioner mechanism. Its fluid damped. Not like it ratchets up to allow for belt stretch. I tend to think the appearance of the noise just after an oil change is coincidental. Cheers E
Good idea Tasks, pull the accessories belts off. I have heard this before I am sure. It wasn't engine related. The engines just kept going no probs.
Owwwhh....that cold water down my back. You are correct the noise does relate directly to degree of acceleration, and it is in sync with engine revs. I've checked all of the timing belt pulleys and they are all good. Checked the magnetic oil plug and no sign of any significant metal in the sump. I will have a closer look at the other belt driven mechanisms on the engine, but I really don't think it's there. I realise others are at a disadvantage as it's very hard to diagnose using just an online audio file. In person the sound did really sound like it was coming from the front drivers side (where the dodgy lifter is) of the engine. After moving the valve clear of the cam lobe what I imagined was happening is that lobe coming around and slapping the lifter.....harder as the revs increased? Don't know for sure. Either way best way to find out now is to replace the lifter, put her back together and cross my fingers. On another note, I called Nissan Aust to get a price on a single lifter...$130....man we get ripped here in Aust. I'll be ordering through CZP.
I would say the lifter would have to be completely rooted. As in its fully discharged and no oil is getting in maybe. Then again most lifter noise I have heard goes away with rev and load. I have fingers crossed for you Marcus.
Look in the For Sale section or put a Wanted for a lifter. People wrecking motors all the time. A lot cheaper to get a second hand one to try than buy a new one and find out it's not the problem. Good Luck Dave
