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Nissan knock?

Posted: Fri Jan 21, 2011 9:44 pm
by charlie
Hey dudes. My kid brother is starting to worry about the knock coming from his engine at startup and I told him I'd ask the pros. It's an '02 Sentra SE-R. He says when it starts it up it knocks really loud and it's starting to make him worry. A little googling tells me that it's a common Nissan issue and that it's not something he should lose sleep over as long as the knock goes away after the car warms up but I figured I would see if there's something else he could do or if you think he should get it checked out anyway.

Is there a specific weight or brand of oil he should go for to help reduce the noise? Also, he lives in Dahlonega in case you know of a good oil-change spot.

Thanks bros.

Re: Nissan knock?

Posted: Fri Jan 21, 2011 9:49 pm
by Greg
piston slap? how many miles are on the ticker?

he could try switching to a heavier oil, I recommend Rotella, the same stuff semi trucks use, swat I use in the WRX

Re: Nissan knock?

Posted: Fri Jan 21, 2011 11:35 pm
by Generz
have him check his oil level..

20w50 should reduce the knock..

have him let the car warm up to temperature before driving it..

Re: Nissan knock?

Posted: Sat Jan 22, 2011 1:10 am
by Inappropriate Chris
I have heard of the cats clogging and causing the motor to let go.

Re: Nissan knock?

Posted: Sat Jan 22, 2011 1:59 pm
by boostbeef
If it's a knock that goes away after the car warms up, it's probably piston slap. Not much you can do to fix it, but it doesn't do much harm if it only happens during the FOERST few seconds after cold start-up. If it continues to knock for several minutes though it will eventually scratch up the cylinder walls and need to be serviced. This is a common GM problem and several people have tried to file lawsuits over it and get them to recall the motors.

Just make sure not to put any kind of load on the motor till the knock goes away.

Personally I wouldn't put a thick oil into the motor. To me it would do the opposite of what you need. While a thicker oil will quiet the issue more, a thin oil will flow faster and lubricate the cylinder walls quicker and make the noise go away. I would just go with a 10w30 syn oil.

Re: Nissan knock?

Posted: Sat Jan 22, 2011 2:36 pm
by Generz
Thicker oil will lessen the knock.. how? Because it dampens more....
How do you dampen the noise? By having a thicker coat of oil coating the surfaces.

If thinner oil lubricates better.. then why aren't we running some advanced formula of KY Jelly in our cars?

Re: Nissan knock?

Posted: Sat Jan 22, 2011 2:41 pm
by Greg
Kentucky Jelly tastes nasty, duh Geners

Re: Nissan knock?

Posted: Sat Jan 22, 2011 3:28 pm
by charlie
He said he's got 112k on the clock. I'll pass along the advice and make sure that he's not taking it to Commerce or anything while it warms up.

So then the weight?

Re: Nissan knock?

Posted: Sat Jan 22, 2011 4:41 pm
by Cankles
Johnny Tran: [interrogating Ted about his missing engines] What are feeling, Lance... 40 weight? 50 weight?
Lance Nguyen: 40 Weight sounds nice...

Re: Nissan knock?

Posted: Sat Jan 22, 2011 5:25 pm
by icantdrift
could be several things.

1. timing chain slapping, shitloads of nissan engines get this (aka damn near every KA motor and my dad's maxima has done it for the last 50-60k miles). basically the chain tensioner is hydraulic and it gets clogged up over the years and the plastic chain guides also get worn down. when the engine is cold it won't pressurize with oil properly and the chain has a bit of slack then slaps against he guides causing the noise.

2. piston slap, as previously mentioned. metal contracts in cold, so on startup/warmup everything in the engine is loose as a $2 hooker. once it warms up everything comes back into an acceptable range and the noise goes away. being that he's in Dahlonega it really shouldn't be cold enough for this with that low of a mileage unless that thing was really poorly maintained over the years.

3. hydraulic lifter tap. not really a "knock" but one man's tap is another man's knock. same idea as the hydraulic tensioner issue, the oil orifices for the lifters get gunked up and cold oil is pretty thick. the lifters then don't pressurize when cold leaving slack between the lifter and cam, and when the cam lobe hits it it will tap pretty loudly. once it warms up the oil is able to flow into the tiny holes and pressurize and all is well.


Tell him to change his oil and use a lighter weight oil if he's running over 5w30 during the winter. There's also an oil additive called BG MOA that can help clean out the clogged lifters/tensioner issues. That stuff worked wonders on my miata when i had it. if it doesn't get better after running the additive through a couple of oil changes then parts likely need to be replaced soon.

Re: Nissan knock?

Posted: Wed Jun 13, 2012 12:01 am
by charlie
Advice time again if you guys have a sec. Long story short: brotherman's engine finally took a shit.

I feel bad about the whole thing because I'm the one that told him the SE-R was going to be a cool little reliable car for him. I think he got his money's worth out of it, but I guess the previous owner just put it through a little too much abuse. Anyway, what would you guys do?

The car (2002 SE-R Spec V) is in decent shape body-wise, but another engine is going to be around $3500 installed (not sure yet on the mileage of the engine he found). So would you guys cut your losses and try to move on? or put up the 3500 and try to get another 3 years out of it? What's an SE-R even worth, not running? A 12-pack? He doesn't really care much about cars, just wants some reliable transportation while he establishes himself here in Chicago.

Your guidance on shit like this, as always, is much appreciated.

Re: Nissan knock?

Posted: Wed Jun 13, 2012 1:05 am
by Generz
best thing is let's see who has some automotive contacts up in the Chi-town area.. I think a decent used motor can be bought and installed for cheaper than that price.

Re: Nissan knock?

Posted: Wed Jun 13, 2012 12:40 pm
by FooSchnickens
Sentras of that period are notorious for this issue, but only with one specific motor. Not sure if they used the same on in the SE-R, but it's possible.

If it were me, I'd dump it. Try putting it up on GRM or or other racing board, those chassis are pretty stout and only need a little prep to be competitive in various motorsports. I don't know what they go for blown, but he'll probably get a lot more for it from there than a "we buy junk cars" type setup.

Re: Nissan knock?

Posted: Wed Jun 13, 2012 4:22 pm
by charlie
Generz wrote:I think a decent used motor can be bought and installed for cheaper than that price.
Oh, really? That sounded about normal to me but I guess I'm kinda clueless. The mechanic is a family friend, so I just figured it was about right. I looked up engines in the area (ATL too just for shits and giggles) and all were were around 1800-2500. He just told me the engine in question is actually an '04 with 71k, but now that the acceptance is setting in, I don't think he's going to go for it.

Foo, you may be right. I think we might just need to slide this one on to someone who adores the SE-R and like to tinker.

Time to go scooby shopping. :winky:

Re: Nissan knock?

Posted: Mon Jun 25, 2012 1:22 pm
by charlie
charlie wrote:Time to go scooby shopping. :winky:
I think I see a way out of this.

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