Light knock at idle when cold

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tommymonza
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Light knock at idle when cold

Postby tommymonza » Wed Apr 13, 2016 11:57 am

I have a 08 with the v6 with 120000 miles on it. I have owned d since it had 70 thousand.

Always the best oil and napa gold oil filters changed regularly. Never abused or over heated.

I can't imagine it is a rod knock.

Almost light enough to be a lifter noise but no lifters in a doc engine.

Never had the timing chain done, do you think that is what I may be hearing.

I think there is a bracket for the exhaust that is cracked that creates a vibration noise on acceleration from what I have read , so easy fix there.


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smj999smj
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Postby smj999smj » Wed Apr 13, 2016 2:00 pm

It's hard to say without hearing it, but if it's only when you start it up cold and goes away fast, it could be "piston slap," which is fairly common in these and several other engines. My '06 does it every now and then and so did the 2.7L Toyota engine every winter. If that's what it is, there's nothing to worry about. It's not a sign of your engine getting ready to grenade or something that will cause bigger problems. I doubt highly that it's the timing chain. If it is, you will hear a "whining" noise that increases and decreases with engine RPM; the noise is not unlike a bad power steering pump "whine."

Kestral
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Postby Kestral » Wed Apr 13, 2016 5:15 pm

My 2012 with 40,000 miles seems to have a slight "knock" or noise when it's real cold out. I just drive real slow for a few minutes and wait for the temp to come up and it goes away.

My old Jeep Grand Cherokee 4.0 inline 6 did the same thing I drove that for over 200,000 miles so I guess the noise did not matter so much.

tommymonza
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Postby tommymonza » Fri Apr 15, 2016 7:27 am

How long will the timing chain go after you start hearing the whine and what will happen if you don't fix it!

Also at 120 thousand is there a good chance it won't make the noise or that the previous owner of 70 thousand miles had it repaired and now it is good for 300 thousand?

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smj999smj
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Postby smj999smj » Sun Apr 17, 2016 5:11 am

tommymonza wrote:How long will the timing chain go after you start hearing the whine and what will happen if you don't fix it!

Also at 120 thousand is there a good chance it won't make the noise or that the previous owner of 70 thousand miles had it repaired and now it is good for 300 thousand?
Not every V6, R51 Pathfinder will have problems with the upper timing chains. The chains that have the issues had links stamped with worn dies. As the dies wore, they created sharp edges on the links, which cut through the plastic tensioner "feet." Depending on how many stampings were on the die correlated to how long it took the chain to cut through the plastic tensioner feet, if they did, at all. That's why there is no mileage range for when the failures occur. Some have cut through to the steel plunger in less than 40,000 miles and some have occurred well over 100,000 miles. If you don't hear the "whine," then don't worry about it until you do (if you ever do). For that reason, it's also impossible to tell how long after you hear the noise to determine how long it will be to it turns into a catastrophic failure. In the worst case scenario, the chain will jump timing, valve heads will collide with the pistons, at which point they could break off and grenade the engine...or simply bend, requiring head removal and a valve job (an expensive and difficult job, in itself). If the chains have previously been repaired with the updated parts, you shouldn't have to worry about the issue, again.


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