Many members have posted about engine knock when the engine is fully warmed and at idle. I have experienced this (still do) and even took my Max to the dealer for service. They said it was normal operation for the engine... they did agree to replace a fuel damper, but this did not fix the issue.

I had given up and just dealt with it until I found NTB12-071.
http://x.nissanhelp.com/forums/Knowledgebase.html?catid=627

It requires the replacement of a crankshaft main bearing. I have not seen anyone else post on this NTB and wanted to get this out there for anyone with the "engine knock" issue.

This NTB is an extremely lengthy procedure that is just short of taking the engine out of the car. Many parts need to be removed, fluids drained, etc.

My question is if you think it is worth the risk of breaking all the factory seals so to speak... removing parts, trusting nissan mechanic to reassembly, etc. to get this issue fixed. Will it cause damage if left alone? It is a main bearing, so I have to think eventually there will be consequences if left unaddressed. I have done several used oil analysis that all show very low wear levels... but I'm concerned that over time the main bearing will wear and cause catastophic engine failure.

What would you do?

 

What would Jesus Do? He would of probably bought a Prius and called it a day.

I think I am starting to experience this knock..and a whining noise as well. For you if you are under warranty, take it to the dealership and be done with it. However, I warn you that your car may never run smooth again and I am sure they'll dirty the interior and dent a door or two. They are quite clumsy. For me..I have no warranty, and well I'll just go and buy another car lol!

It all comes down to what you want to do..not us on the forum.

 

I do not think I would be concerned about the car not running right again. All the seals that can be replaced will be and the others are FIPG.

This really is a big job...but just replacing one main bearing isnt enough to change anything about how it will run. If dealership will do it without fussing too much, I would let them do it.

The bearing space being too large isnt really all that big of a deal PROVIDED its not out of spec far enough to drop your oil pressure and flow to the rest of the engine. With good oil samples, this isnt the case. The only reason we hear it at idle is because oil pressure is low. I dont really know that its a problem when rpms are over idle.

Late,
Trav

 

Thanks for the response... I've contacted another member that said he was having his main bearing replaced... waiting to hear back. I agree with all of your points and feel a little better due to my used oil analysis, but if the knock is that loud, I feel like there has to be damage occuring. If the oil film was thick enough or oil pressure was high enough, I wouldn't think the engine would knock. Like you said, that's why it only does it at idle. Is there anyway that the oil pressure is sufficient to prevent metal on metal contact but still produce the noise. If so, what is "knocking" together to create the noise?

 

Ya know...I have wondered that same thing myself. You sure would think that a proper and safe oil film there would prevent any noise unless there was metal-on-metal contact. There apparently is not, though since that would show up in a UOA. I have 67,000 mi on mine and if there were metal-on-metal contact, there's no doubt it would have spun long long ago....you would think.

I don't know. I haven't gone and talked to the dealership, yet. I am dreading arguing with them since I am out of warranty.

Late,
Trav