Chirp from 5.0l with alpha drive

[lkbum]

I have a 2001 chaparral 280 ssi with twin 5.0l and alpha drives. I have a low frequency ( roughly every 4 seconds ) coming from the starboard engine. It is a "chirp" as opposed to a squeal or squeak. What bugs me (other than not knowing what it is), is that I cannot find anything on the engine that would have that time before chirps (like a belt going over a rough spot on a pulley). Definitely only comes from the starboard engine. I can't really see if it varies with rpm as once above idle the engine noise drowns it out. Any thoughts?

 

[Fun Times]

Re: Chirp from 5.0l with alpha drive

You could try removing the belt and spin what components you can by hand as a test to see if you can get lucky finding it that way.

Good luck.

 

[Don S]

Re: Chirp from 5.0l with alpha drive

Have you opened the hatch and actually followed the sound with your ears to hear if it's coming from the back or front of the engine?
Mechanics stethoscope could also help you locate the sound source.

 

[lkbum]

Re: Chirp from 5.0l with alpha drive

Have you opened the hatch and actually followed the sound with your ears to hear if it's coming from the back or front of the engine?
Mechanics stethoscope could also help you locate the sound source.

Yes, that's the first thing I did. Since I have twins in a fairly small boat (9' 4" beam), it's not that comfortable crawling around a running engine. My first reaction was that it was the engine hatch or something similar that was rubbing. I think I elminated that because the sound only occurs with the starboard engine running and with the hatch opened or closed (it is a large hatch). The sound "appears" to be coming from the rear of the engine. It makes the noise in neutral and in gear. I timed the chirp to try and figure it out also. The first time I timed it, it was approximately 4.6 seconds between chirps, very repeatble. About an hour later, it was just under 4 seconds. Maybe I have a bearing in one of the pulleys or accesories on the belt that is going bad, that's the only thing I can come up with. Can you think of anything else in the engine/drive that would see a 4 second period? I did not time the serpentine belt, but watched the markings on the belt traverse the various pulleys and the chirp soes not appear to be in phase with the belt. So one again, maybe a bearing that does not have a rub that occurs every revolution?

 

[cecho]

Re: Chirp from 5.0l with alpha drive

I can't think of anything on the engine that has a 4+ second period at 600+ RPM. The longest period I can think of would be the camshaft and distributor at 0.2 second period. Being that the accessories pullies are usually the same size or smaller than the pulley attached to the crankshaft (0.1 second period), those device will have even shorter periods.

I guess it's possible a bearing going bad could cause a chirp like that if you had a single bad ball bearing hitting a specific part of the race or both races on a multiplication of the shorter rotational periods. A rotational period of 40:1 or less is certainly possible in that case.

Here's a bearing gif with a rotational period of 3:2 to illustrate what I mean:
http://images2.wikia.nocookie.net/__cb20100110165829/skateboarding/images/3/30/BallBearing.gif

Your best bet at finding the noise is to follow your ears. What happens when you remove the accessory belt? Unless there's something odd on that engine I'm not aware of you can run the engine without the water pump, alternator and PS pump running for a short time.

 

[lkbum]

Re: Chirp from 5.0l with alpha drive

I can't think of anything on the engine that has a 4+ second period at 600+ RPM. The longest period I can think of would be the camshaft and distributor at 0.2 second period. Being that the accessories pullies are usually the same size or smaller than the pulley attached to the crankshaft (0.1 second period), those device will have even shorter periods.

I guess it's possible a bearing going bad could cause a chirp like that if you had a single bad ball bearing hitting a specific part of the race or both races on a multiplication of the shorter rotational periods. A rotational period of 40:1 or less is certainly possible in that case.

Here's a bearing gif with a rotational period of 3:2 to illustrate what I mean:
http://images2.wikia.nocookie.net/__cb20100110165829/skateboarding/images/3/30/BallBearing.gif

Your best bet at finding the noise is to follow your ears. What happens when you remove the accessory belt? Unless there's something odd on that engine I'm not aware of you can run the engine without the water pump, alternator and PS pump running for a short time.

Thanks for the illustration. Will pull the belt this weekend and seemwhat I find. Thanks again.