Engine Knock.......Again. Need advice.

[TXT]

So today I got the infamous engine knock in the 8 cylinder engine. About 4 weeks ago I topped off my oil at the dealership. I was low 2 quarts. I use synthetic. Today I did a semi hard acceleration and the noise came....loud. Stopped at the nearest dealership which happened to be a Honda. We put 1.5 quarts and the dip stick showed the oil in between the two dots. I let the car sit for a while then started it up again but knock was still present. I drove it 40 mins back home 65 mph average speed. When I got home, the engine knock was gone but the sound is very very faint. Hopefully it gets better in the next couple of days.

Long story short, in 4 weeks, I burned between 1.5 - 2 quarts of oil. This is a cause for big concern for me. This is not normal. I also don't want to keep adding oil because again, that's not normal and that's a sign for something being wrong.

Is this normal for all of you other M45's? I'm at 83K miles right now, perhaps spark plugs might help? Not sure if it will do anything since the spark has nothing to do with oil, just gas and air and spark explosions.

What do you guy's think I should do? I started another thread a couple of days ago about me wanting to get a G37. Perhaps this might be a good time to get one unless there is a fix for this. I understand this engine burns oil, but the amount my engine burns is NOT normal!

[White-Rush]

fux that... Trade it out. IJS

Can't remember from the other thread ( are you still in extended warranty? )

[TXT]

fux that... Trade it out. IJS

Can't remember from the other thread ( are you still in extended warranty? )

nope. No warranty at all. I got this car a year ago.

[White-Rush]

If you are not mechanically able to do a full diagnostics of what is wrong, I say have a shop take a look at it (i'm guessing this will cost $80 to $160). And from there, if it's something serious you can make a decision on whether or not you want to trade or repair.

[svard75]

I'm really surprised at how people measure oil level. You can't drive it around hard pull the stick for measurent and say I'm low then add oil. The oil is still in the upper cylinder and in some parts of the engine still. The best time to measure true oil levels is on a flat surface the next morning before you start the engine. Too much oil and the engine could starve (from too much oil frothing). You could also be causing the engine to build up too much pressure and can have a negative effect on piston seals.

Do you see blue smoke coming out of the back? When was the last time you emissions tested it? The knock could be because the engine oil has gummed up and is blocking ports. Have you heard of sludge? I would go and get the engine professionally flushed and try again.

Also engines have knock sensors which retard timing. You would notice a huge power loss if it really is knock.

[mexillis]

I've had it knock on me before a couple times during start up. Once was in the winter and another time was when I didn't drive it in a while. I'm at 110k now and have had oil consumption from 1-2qts during my ownership. Idk what causes it but there are a lot of posts about it. I do know that mobil1 isn't good for my car as that's what seemed to disappear the fastest when I was changing oil at 3k miles. Ever since I switched to royal purple I have rarely had to top it off and don't change it until 6-8k miles depending on how I drive. Some have switched to non synthetic but that's not something I'd want to do since my "fix" is working with synthetic. One other thing that will help with removing a blue smoke start up is the oil catch can. I have driven over 20k since i put that in and haven't needed to empty it yet but others have had it fill rather quickly. If you're going to trade it in so soon from owning it maybe an M37 would be a compribal exchange? GL.

[TXT]

I checked the oil level this morning before start up. The oil level was a bit below the top dot of the dip stick.

It now makes the same knocking/ticking sound that was present yesterday. Loud enough for other drivers to look over.

There is blue smoke at start, but not all the time. I can't say if I have engine loss since I was baby-ing the car yesterday. The engine however does sound normal and idles fine and "acts" as it should if you take that knocking sound out of the equation.

As far as the oil catch can, I am very mechanically impaired. I would however attempt to do this if I had a very thorough and detailed DIY. There is one here but that is for the 6 Cylinder I believe.

[White-Rush]

Just throwing this out there, but do you think it could possibly be bad fuel? I know that some engines will ping / knock like crazy if the fuel is dirty or watered down. I'm no expert on these matters, but I do know that this is true for "some" engines.

[TXT]

Just throwing this out there, but do you think it could possibly be bad fuel? I know that some engines will ping / knock like crazy if the fuel is dirty or watered down. I'm no expert on these matters, but I do know that this is true for "some" engines.

I don't think this is the issue. I have been getting my gas from the same place since I purchased the car. I go to Shell and put premium all the time.

I think I'm going to go to Firestone (not sure if thats a good place) since there is no other good places to take it to in my area. I'll have them check to see what the problem may be even though I kind of know what it is, and I'll have them "flush" the oil and diagnose the sound. I really love this car I don't want to get rid of it!

[TXT]

Would adding a small amount of seafoam in the oil right before I go get an oil change clean things out?

[svard75]

Seafoam is a good additive, however I would do this at the place where you're having the oil changed. You don't want to put load on an oil poor engine. I would also ask them to drop your pan and have a look at the screen. Replace the Pcv valve and clean all the hoses out. Sludge would not buildup unless you have no air in the crankcase. You have that catch can right? Does it allow air back in?

[TXT]

I don't have a catch can. The engine is completely stock with no modifications. I'll ask them to do the above tomorrow.

[svard75]

Before you go take your car on the highway and drive it hard for a few hard pulls. Are your trips mostly short city?

[TXT]

Before you go take your car on the highway and drive it hard for a few hard pulls. Are your trips mostly short city?

I usually have a 25 minute drive to and from work monday through friday. All highway. I don't drive my car hard but yesterday was the rare occasion where I did a hard pull from a stop and this happened. Seems as though this problem only occurs when the car is not in motion and the throttle is pressed hard. If I'm at highway speed and I press the throttle hard this will not happen.

I'm not sure if hard pulls will help, but then again maybe thats just me being a scaredy cat! Are you suggestion I do an "italian tune up"? Get rid of possible carbon build up?

[svard75]

Lol. Haven't heard that term in ages. More to burn off any residual oil and to make sure the engine is hot before the seafoam. What oil have you been using? This might sound bad but I've heard that some guys that lease cars never change oil. Was your car a lease?

[TXT]

never a lease. I have the service history. Always serviced at infiniti. I noticed the PCV valve was changed once but that was years ago. It showed up on the service history.

[svard75]

Change that out as well but bring the oem part with you.

[TXT]

On the way to a shop this morning, I drove the way I normally would. Instead of going on the highway and doing some pulls, I just drove normal when compared to the way I did Saturday when I babied the car.

The sound went away.

I will update this thread If needed.

[TXT]

Update:

Car has been off for 3 hours. I went out to start it again and the sound came back for a second at start up, and appears again when I rev and it reaches the highest point of my rev (highest point was 3k RPM).

Seems as though, from what I can observe, if the car is at operating temperature and in use, the sound is gone, but as it cools down the sound gradually comes back. When I turned on the car, the temp gauge was still around the halfway mark.

Another note to mention: On Saturday when the noise first appeared, after driving home (35 minute drive), the sound was almost completely gone. I turned it on about 3 hours later and the sound was back back in full effect! This was after topping off the oil.

I will have to wait till' tomorrow and see what happens after the engine is completely cooled off overnight. I will however add more oil and fill it to the top dot of the dip stick. This may not be advisable, but I'll end up burning it off in a short amount of time anyways. I just want to make sure I lubricate everything in the engine!

[svard75]

Here's something useful about oil levels.


"What happens when an engine is overfilled with oil?

So you topped up the engine when it was warm after getting a faulty dipstick reading, or you put too much oil in when you changed it yourself. What's the worst that could happen? The problem with this is that the next time the engine is run, the windage in the crankcase and other pressures generated by the oil pump, etc. place a great strain on the seal on the rear main bearing.
Eventually, often much sooner than the ordinary man in the street might expect, the rear main bearing seal ruptures, and the engine becomes a 'leaker'. If you've got a manual gearbox, this means one thing: this oil goes right onto the flywheel and the face of the clutch disc. A lubricated clutch is A Bad Thing. If this still goes unnoticed, the front seal is the next to go, and the engine then becomes a 'gusher' (or to be more colourful, it starts pissing oil all over the place). As well as smothering the clutch with oil from the rear, the oil now coming from the front leak will be neatly distributed about the engine bay as it hits the front pulley - often propelling it out as far as the brake discs. At the same time as this Hollywood disaster movie is unfolding outside the engine, things aren't working out any better on the inside. As you can see from the diagram, the correct oil level is really close to the rotating crank. Overfilling will mean the crank dips into the oil and churns it into a froth. Froth is good on certain types of coffee but not good in an engine. The mixture of aerated oil will be forced into the bearings and in case you didn't know, air is not a lubricant. Typically this means that bearing damage will follow quite rapidly, especially if you are driving on a motorway. You'll know bearing damage when you get it. The engine smells like a garage mechanic cooking over an open flame and the noise coming from the engine is the sort of thing you'd normally hear in vaudeville plays when a piano is pushed down a flight of stairs. As if that all wasn't bad enough, the excess oil gets thrown up into the piston bores where the piston rings have a hard time coping with the excess oil and pressure. It gets into the combustion chamber and some of it will get out into the exhaust system unburned resulting in a nice patina of oil all over the platinum surfaces of your catalytic converter. This renders it utterly useless for good.
Well, you did ask.
So what's the best way to check the oil level?

If your engine is cold (for example it has been parked overnight) you can check the oil level right away. The oil will have had time to settle back into the sump. Just make sure the car is level before you do. If the engine is warm or hot (after you've been driving) then you should wait for 30 minutes or so to let as much oil as possible drain back into the sump. Checking it first thing the next morning is ideal.
It's worth pointing out that you should double-check your owner's manual too - some cars, like I the '92 Porcshe Carrera, require that the oil is checked while the engine is running and the oil is at temperature."

Reference http://www.carbibles.com/engineoil_bible_pg2.html

[TXT]

Ok, so far today this is what has happened.

Turned on Car in the morning. Heard the knocking sound.

Went back out 5 minutes later and the sound was almost gone at idle approaching the car. Inside the car it was very low. At take off the sound was back. I drove normally and it went away all together.

I go to work and turn it on at lunch time for a few moments, sound was sort of there, but hardly noticeable. Temp gauge a bit less than half.

I leave work and the engine is completely cold. Knocking sound begins loudly. I take off without letting the engine heat up (on purpose) and the sound goes away about 10 seconds later all together. My 35 minute drive was absent of the sound the entire way. I also did some hard pulls and the engine acts and sounds the way it normally has been acting.

I stopped by Advanced Auto Parts. I purchased a can of seafoam and put it in the gas tank just in case. Although I doubt it will make a difference, it's worth a shot! I also bought Lucas Oil stabilizer that I won't put in until a couple of days before I go trade out the car. I won't feel to bad having a dealership take the car from me. That might sound bad but I feel like I have no other choice.

I'll turn the car on tonight and see if anything has changed. Previously, it took a couple of minutes of driving to get ride of the sound, it seems to be reducing in time.

I was told that when I accelerated hard with low oil, possible engine slush may have clogged a passage way that allows oil to flow through the engine. This may be true which is why I did some hard pulls to see if anything might get unclogged. An engine flush was also recommended 5 minutes before I change the oil.

After some google searches, "Piston Slap" seems to be the most accurate description to the problem I have now. With Piston slap, the knocking sound appears but after warming the car up, it disappears.

Thoughts on all this? Like most of you (msvara included), I do not like making some serious decisions without some feedback from a couple of people including google searches.

[svard75]

I don't think it's slap. There were some engines that produced slap while cold until the pistons rings warmed up and expanded then it would go away. It's consistently there your noise isn't. When you hear the ticks did you try a hard pull? Does it feel exactly the same? Without actually hearing it I would venture a guess that the heads are what's making the noise. But anyway it sounds like you're ready to trade it in.