|
isb360 I started hearing a rattling sound upon startup. Each week the sound got louder. I assumed it was the timing chain so I took the rocker cover off and examined the chain, guides, gears etc. and everything looked fine. Then I noticed about an 1/8" diameter chip out of the cam right next to the gear where that peg is that aligns the gear. There was also a hairline crack trailing from this chip. So I knew the cam needed to be replaced before something nasty happened, if you know what I mean. After I removed the cam gear I discovered that the the cam gear peg was loose (I actually pulled it out by hand), and that circular lip on the end of the cam that goes into the cam gear had actually broke/wore away (nothing at all was left). I imagine this made the cam gear somewhat off center. Was that living on borrowed time or what! The funny thing is when I was checking the chain, gears etc. I did not notice the cam gear being loose. Also, when I loosened the cam gear bolt it did not seem anywhere near loose (I had to use a good amount of torque to undo it). This makes me wonder how it wore away if the cam bolt was tight. Also, the car ran descent other than the noise. After thinking about this for a while I begin to wonder if this is some sort of defect that nissan knows about and often chalks it up as damage from a timing chain failure, when in fact this situation might be what's causing the chain to fail. It has always baffled me why this motor requires timing chain changes (at I think, every 60K miles)and seems to have a high rate of chain failures compared to other vehicles. After all, a chain is a chain, and other vehicles have then. If you look at the cam where that peg goes in there is not much distance between it and the outer edge of the cam (thin, and the peg only goes in about 1/4"). Also, if you look at that lip on the end of the cam, it only goes in about halfway into the cam gear and is fairly thin also (not good engineering in my opinion).
Perhaps the cam gear bolt was ever so slightly loose and it let the gear move under high torque, but I sure didn't notice it when removing it. On the otherhand, maybe there is a design flaw here. Who knows?
Anyway, hope you didn't mind the lengthy response. If you or anyone has ever come across this type of situation post a reply and let me know about it. Also, for anyone doing any work under the rocker cover I would recommend checking that cam gear peg area very closely!
|
Linear Mode
