Hey guys im new here, i have a question on a knocking sound at idle. What are the main things that could cause it to make that sound? I was thinking the crank pulley but then again whats the difference between the crank pulley and a harmonic balancer? but other then that the car runs fine, although i feel like the car has some hesitation starting up and no clue why. its a 2000 nissan maxima se mt btw. no mods yet at 173xxx.

 

First thing I recommend is getting it compression tested. If you've got hesitation starting up, and a knocking sound, you need to be prepared for the possibility of needing a rebuild or at least an overhaul. Knocking, by my assumption of knocking, indicates an issue with the lower internals of the block, usually rods, or rod bearings.

A harmonic balancer, to try to put it simply, is a damper or bearing (for lack of a better word) that absorbs vibrations, and other movements that cause crankshaft imbalance over time. A crank pulley is exactly what it sounds like, it is a seat for the belt allowing it, in this case, to drive the accessories (ac, ps, alt, etc.).

A bad harmonic balancer can, in some cases, be worse than just a solid pulley with no damper. So if it's bad, I would recommend replacing it soon.

The easiest way to tell is to start the engine up and stand directly over the top of the pulley (or you can jack the car up, and look at it straight on, though I don't ever recommend putting your face directly under a spinning pulley) and see if it appears to be wobbling at all. If the harmonic balancer is worn then the whole pulley will wobble a little.

Now, I had a Mini Cooper S come into the shop a while back that needed a harmonic balancer because the one that was on the car was spinning inside the pulley. So the pulley and balancer were actually separated causing the car to be revving higher than it could drive the accessories to power it.

I know that's a bit of a novel, but I hope it helps. Get that thing compression tested, check the balancer/pulley, and let us know what happens.. By the way, any trouble codes?

-Nathan

 

I appreciate your reply. I cant quite figure which one is the crank pulley/ harmonic balancer. I have uploaded a video of the sound and a look at it from my point of view.
http://s1072.photobucket.com/albums/w366/sek11172/ , If you could take a look at this video and share your input it would be great. The first object in the video looks like the one that is not %100 could you and then theres the smaller one closest to the alternator that seems fine. Which is which is one of my questions. Also thanks to Nathen.

 

Would it even be worth for an engine rebuild? its my first car, im looking to drive this maxima for the next 2-3 years or even more. I bought it for $1400 and installed a new clutch, new tires, muffler, starter with all that ive put about 4500 dollars into this car almost 5k. And the same thing happened to Kidcymucks 2001 se starting problem happend to me if youve read his thread. im not looking to spend another 2k or more on this car.

 

Well, I couldn't see much in that video, but I can tell you that the harmonic balancer and crank pulley are essentially one in the same. It will be located directly in the center of the block at the bottom.

One way to tell whether a rebuild would be a good idea is to get a compression test done. If the compression shows up low in one or more cylinders, obviously, it's time for a rebuild. Honestly though, you might be better off replacing the engine with a good condition used one. It will be cheaper, and a lot less work, which means less money spent and less time out of a car.

If it's just the harmonic balancer, then it can be replaced, but you will need a special puller to get it off.

-Nathan