What is this sound, sounds a bit concerning

[tuccitown]

Hi All,

I have been getting the coach ready for a trip and will go into more details in another post. On the way home from the last trip about 80 miles out of town durning a stop I heard a concerning sound during my walk around. It seems to me that it is coming from the rear of the engine. It only appears to be the loudest at fast idle although I can hear it at idle but also seems to go away at higher RMPs.

Any ideas what could be making the sound I have attached files from two locations at high idle and low idle.

https://youtu.be/L7lG2v0qqpM

https://youtu.be/aU7eobWw8QE

https://youtu.be/-awP8VfyWRc

https://youtu.be/0duWbKi4F7Y

1955 Sciencecruiser 8v71 740

Thanks,

[chessie4905]

Try using a piece of hose to your ear and probe around engine to better pinpoint the general area.

[brmax]

First one worries me, requires lots more lookin and listening. Im hearin gear
Second in there has to me a belt /rubber sound
Third im noticing a single exhaust leak, pat pat
Fourth i dunno
Finally to say everyone has their own refference, I do wish ya good luck.


Floyd

Edit: I listened to the first one again and few times; the scraping as any coupler and gear on a housing, Im leading more to non metalic so would look at v-belts and their alignment and pulley systems.
You might have considered selling tickets 

[DoubleEagle]

Sounds like something scraping or rattling, it does not seem steady enough to be an exhaust leak. Either vibrations are shaking something, or the pulleys or belts are rubbing somewhere. Perhaps a idler or pulley bearing starting to make noise. Check for anything that is loose, and spray light oil around anything turning to see if the noise changes. Seems to me that the noise is external to the engine, and not from within.

[luvrbus]

Sounds to me like the $25.00 fiber coupling on the power steering pump has lost it's will to live  

[HB of CJ]

Sorry to say it sounds like a loose bearing.  Possibly a water pump also.  Sometimes the bushings or bearing go out in water pumps but they have not started to leak yet.  Might also be a bearing in the cooling fan.  Sorry again.

The check for this is to shut down the mill and put on some thick gloves and try to wiggle the various parts that have accessible bearings.  You will need a pry bar to see if the water pump is loose.  Same with the fan bearings.

Sorry.

[Lee Bradley]

I would pop the belts off and try it. That will remove several sound sources.

[Jim Eh.]

Does the sound level/intensity change between building air and when the air compressor is in unload stage?

[Lin]

Could be a bearing, but I would seriously look for some simple scrapping before anything else.

[buswarrior]

On your behalf, I am hoping it is something belt related.

The variable rhythm has me thinking something loose or hanging and touching periodically.

like a religion, trace the length and circumference of the belts, on the hunt for anything that may touch, or anything loose. 

I like the "remove the belts and run it" diagnosis strategy next.

happy coaching!
buswarrior

[Lee Bradley]

Could be a bearing, but I would seriously look for some simple scrapping before anything else.

Really. You think he scrap it.      Scrape? Would be scraping and I didn't say anything about adjusting the breaks.

[Lin]

Really. You think he scrap it.      Scrape? Would be scraping and I didn't say anything about adjusting the breaks.

Damn it, I have wasted another "p".  I hope that I don't run out!

[Lee Bradley]

Some day you'll wish you had those Ps. 

[tuccitown]

Thanks all for the replies, I decided against taking the coach on this trip until I had time to diagnose the sound a bit more. I will go ahead and remove fan belts as suggested and test. I had planned to do that anyway as I will leave the factory AC belts off and I have to remove the radiator fan belts to get the AC ones off. I will be doing that this weekend and will update on my findings.

Thanks again.

Jack