Hi all,
I have a 94 Altima with 173,000 km. Lately I've noticed some noise from the timing chain area at idle. It's always had some noise there, but it seems like it might be more pronounced now. Basically it's a sort of threshing mechanical sound, but it's got a sort of "beat" to it that happens at a rate of about 4 or 5 times per second at idle. When it's cold in the morning, I also get an occasional "crunch" type sound from this area, but I'm not sure it's coming from under the valve cover or not. I had it checked by the dealer a couple of times, the first time I had it in for service and they checked, but didn't hear anything. They did note that the upper guides had been removed already.
In the last couple of weeks, it's been -18C and below a few days, and I've noticed another sound that's more pronounced than usual (maybe I'm just paranoid!). It's a rotational sound that I can hear only when accelerating lightly or keeping constant speed with little load on the engine.. it almost sounds like a dull metal-on-metal knock... but it's not really abrasive sounding.. I had a water pump go bad on an old Civic, and it almost sounds like that did. I don't know if this is at all related to the timing chain sound or not, but it almost sounds like it could be. I had it down to the dealer last week for a road test with their shop foreman, and he was able to hear the rotation sound once he got behind the wheel, but didn't think it was anything serious. His only real suggestion was that it might be something in the transmission. While I had him trapped away from the dealership, I had him listen under the hood, for the timing chain noise, and he thought there might be some slack in the chain, but again it didn't seem like he thought it was anything critical. I'm fine with that, but it's my engine and I hear it all the time, so it's not as easy for me to dismiss, although maybe I should since he's the expert. I just would hate to have been right all along and have the timing chain snap on me.
Anyone have any suggestions as to what I should do? I guess there aren't many options, but I'm wondering how often anyone's seen these engines blow a chain, and if there's usually any warning sign or not. According to the dealer, they can't really inspect the chain without getting into a lot of work, so if I was going to get them to do that, it sounds like I might as well get the chain replaced anyway.
Would you folks recommend replacing the chain at this age? If so then maybe I'll just do that and put my mind at ease. The car runs great otherwise and still has lots of spirit, so I don't think there's anything really fundamentally wrong with it. If there's anything I could do to maybe help better identify what I'm hearing, I'll do it!
Thanks as usual for the help.