Hey guys, I've been noticing what sort of sounds like a dieseling noise from my engine at idle. It's not that loud, but It's loud enough that when I pull in to the drive-thru, I can easily hear it with the window down. It's been doing this for as long as I can remember. I've checked the oil, and It's fine. I'm also using Premium 92 octane gas. Is this a normal sound? This is my first DOHC motor, so I'm unsure. As I understand it, we have manual/mechanical valves, but they shouldn't need adjusting at 27,000, should they. I hit the rev limiter a couple of times a long time ago, could that throw the valves off? Also, when I press the gas pedal, the noise/pattern increases with the throttle. What do you think?

 

By the way, I go to Jiffy Lube, and I heard that the Nissan oil filter can cut down on some valve noises/problems. An truth in that?

 

There's always some valvetrain and injector noise on the Maximas. Going through the drive-thru the noise is louder because you are right next to the wall and the noise bounces back at you.

If you use a substandard oil filter that doesn't have an antidrainback valve, you might go a few seconds at start up without oil pressure. This might cause some engine noise at start up. This is because the filter is mounted horizontally and the oil can drain out of it while the engine is off. The Nissan filters (and any other filter by a reputable manufacturer) should have the antidrainback valve. In any event, even having the wrong filter wont cause a noisy engine once its been running a while. I use Nissan filters only because the car is still under warranty and if I launch the motor I don't want any crap from the dealer. They'll use any excuse they can to get out of an engine job.

If it's excessive, drain the engine oil and replace the filter and fill the crankcase with 2 quarts 5w30 Motor Oil and 2 quarts Automatic Transmission Fluid. Let the engine idle for 20 minutes (or until hot)- do NOT drive. The lighter oil gets into the valvetrain and loosens up some of the gunk in there. Then drain the oil again, change the filter and refill with the normal oil you use. Should be 5w30 unless you live in a warm climate.

 

It is important to identify the source of the noise. A four-foot length
of small diameter rubber vacuum hose will help you do this. You can buy
the hose in any auto parts store. They typically sell it in bulk for about
US$0.50 per foot. Start the engine and let it idle. Put one end of the
hose in your ear and the other end near any suspected source of noise. The
engine compartment presents a cacophony of sound. The benefit of the hose
is that it isolates the sound from one specific area.

You may find it interesting to explore the sounds of your engine with this
inexpensive tool. Each moving part has its own characteristic sound. For
example, listen to the muted clicking of the fuel injectors. They should
all sound alike. If you find one with a different sound (or no sound at
all) you have found a problem.

The dealer's service department is equipped with high-tech diagnostic
instruments. These are wonderful devices but they are expensive and the
dealer has to recover his cost by charging you for diagnostic time.
Sometimes the home mechanic can do legitimate diagnostic work with nothing
more than a rubber tube.

A wild guess: You will discover that your "dieseling" sound is an exhaust leak.

 

All oil filters have an anti-drainback valve. Good filters have a good valve, and cheap filters have a cheap one.

This has nothing to do with the physical orientation of the oil filter, and everything to do with gravity. If the anti-drainback valve leaks, gravity allows the oil galleries to empty through the filter and back into the sump. If the galleries are empty when the engine starts, it will take a few seconds for them to fill again. During those few seconds the engine is running with zero oil pressure.

I am not trying to pick a fight here, but this is terrible advice. If you can substantiate the validity of this practice as a remedy for valvetrain noise, please quote the authority in sufficient detail for checking. The term "authority" means a vehicle manufacturer or oil company, not your Uncle Harry.

 

1. NO, not all filters have an anti-drainback valve. The only ones that are required to have one are the ones that mount horizontally.
2. Harte Nissan, Hartford CT. Jerry Rome Nissan, Hartford CT. Check with any Nissan dealer - its on a TSB. This was a first step (recommended by them) before we brought the vehicle in for engine work. I work as a tech at an auto auction that sells over 10,000 Nissans a year, and we also have direct ties with Nissan.
3.I don't have an Uncle Harry.
4. Why is this terrible advice? What damage is caused to the engine? Sometimes tricks like these are what prevents costly engine repairs. It does the same thing as Motor Flush but isn't nearly as caustic and is much safer in my opinion.
5. Sometimes the best fixes are the ones that come from years of experience. We have a transmission shop in the area (they do the best work I've seen) that suggested as a fix for a sticking or late shift to spray half a can of carb spray down the trans dipstick tube and then run it. It frees up stuck valves in the valve body in some cases. It doesn't always work, but its worth a try before you go tearing the valve body apart.
6. Perhaps I made a mistake by suggesting he take such drastic measures before he checked a multitude of other things. However, in my line of work I have found it to be common problem with the Nissan V6's - not in just the Maximas, but in the Pathfinders and Zs. We have a responsibility to our thousands of customers (car dealers) to answer for any mechanical problems with the cars that go through our auction. I s--t you not, we have over 100 Maximas in stock right now and I guarantee some of them have valvetrain noise.

 

All 4Gen Maximas have wet-sump engines. That means the engine oil is carried in an oil pan below the crankshaft. The oil pump picks up oil from the sump, pumps it through the filter, and from there fills all the engine oiling galleries. Oil is fed to all moving parts and serves to cool and lubricate them. It then returns to the sump by draining down. Oil in the cylinder heads returns through oil return holes. Oil used for the crankshaft and cylinder walls just drips down.

If an oil filter doesn't have an anti-drainback valve, gravity will cause the oil in the galleries to travel "backwards", down through the filter and into the sump. This is true regardless of physical orientation of the filter. I say to you, politely, that you are wrong on this point.

I value and respect your industry experience. I hope you will admit that plenty of people "in the business" believe in "old wive's tales" and also obsolete information. Your employer sells lots of Nissans, and probably other makes too. Many of those cars have engines with hydraulic valve lifters. Sticky hydraulic lifters are a common cause of valvetrain nose. Sticky hydraulic lifters will sometimes free up when treated with solvent or detergent compounds, including Automatic Transmission Fluid. HOWEVER, this forum is devoted to 4Gen Maximas and the Nissan VQ30DE engine used in all 4Gen cars DOES NOT HAVE HYDRAULIC LIFTERS. The ATF flush you recommended will not reduce valvetrain noise in the VQ30DE engine.

Ask your contacts with Nissan dealers or Nissan USA for the number of the TSB they cited. Ask them if this TSB applies to the VQ30DE engine. Don't let them dance away from this question; it has a Yes or No answer.

Uncle Harry was a figurative reference to someone, anyone, who is not an authority. I don't have an Uncle Harry either.

It's terrible advice because it will cost a few dollars, won't work, and (worst of all) it derails the owner from finding and fixing the real problem.


I agree, completely.

I don't doubt it. However, I do doubt that an ATF purge will eliminate that noise in a VQ30DE engine.

 

I,m not sure about using it in automotive engines but I know that in aircraft, Hydraulic fluid (similar in color and make to ATF fluid) used in aircraft engines would destroy and or ruin any rubber seals in the engine. Wonder if any of this could apply in the same case.

 

Hydraulic fluid is completely different from transmission oil. It's a different weight and has differenct additives and detergents. ATF wont hurt an automobile engine - can't speek for an aircraft engine...
Christ, years ago we use to dump a half quart of ATF into the engine at every oil change just to keep the top end quiet. This may not apply to Maximas but it doesn't have any detrimental effects - other than you might experience some leaking seals. That's from the lighter weight of the ATF oil however. But all this is moot because the ATF is in our Maxima engine for 20 minutes, not till the next oil change.
Well mister D.I.Y. mechanic, I believe oil filters that are mounted vertically are not required to have an anti-drainback valves for the simple fact that the oil would have to travel STRAIGHT UP on its own when the engine is off.

Next time I see the Nissan people I'll ask them for that information.

 

I stand by my previous statements. My position is based on an understanding of gravity, engine construction, and personal experience. I owned a car with a vertically mounted oil filter (not a Nissan) which developed valve clatter soon after an oil and filter change. I diagnosed the problem as a faulty anti-drainback valve, replaced the filter, and the noise was eliminated immediately.