We have the mechanical C-8.3 engine.
While Cindy is driving, I hear, on the curb side of the bedroom, a higher pitched whine, that changes with throttle and is louder on hard throttle.
Seems like a sound the turbo could make, except it is MUCH louder on the other side of the engine. We did pull the turbo input rubber hose, and the impeller looks good, no pits, easy spin, no shinny housing, no play in shaft in all three directions.
The air compressor, air dryer & governor are on the curb side of the engine.
What coudl cause this type of sound?
Don't know, but sound waves can do really weird things when they reflect off surfaces and are transmitted through materials. Can make it very difficult to pinpoint the actual source...
Of the 3 items you mention on the curb side of engine, air compressor "sound" (if any) is the only one that might possible vary with RPM.
I had a situation in really cold weather where I was getting a loud whine on startup and it turned out to be the transmission. Allison could find nothing wrong with it tho. Obviously cold weather is not in play with yours. The only things changing speed that would cause a rising / falling whine would be the turbo and transmission.
To isolate it some try taking off with transmission in low gear and don't change it. If whine changes or never starts that may give you a clue.
Gary B
Try driving with the bed up to locate sound. Use wooden stick from turbo to your ear if you have trouble finding the noise.
Pierce
Could it be the cooling fans rubbing on something?
What about the rear axle components?
Barry,
You will recall that you and John H helped me track down an engine related whine (ours was on the driver's side) in Oregon. It was caused by the outlet from the air cleaner having had come adrift. (Luckily caught before any damage was done to the turbo.)
Grant
What about the air compressor components? Think your pully would change speed with RPM change.
In the last 20 years, not aware of any air compressors that were belt driven-- they are all gear driven.
Last one I remember that was belt driven was the Caterpillar 3208.
Sorry, ment air conditioner.😅
Thanks to all . .
We are heading north toward North Dakota and have an up hill climb from Phoenix to Flagstaff. So we will drive with our bed raised (PVC hold up pipe) and use a length of PVC to my ear to find the source while under throttle.
Will report back what we find.
Be sure to open the windows just in case--- an exhaust leak with the bed up could do you in!
We did our up mountain/hill test drive from Phoenix to Flagstaff with bed up part of the time.
I did not locate any source of the whine that we can hear when bed is down. With bed up engine is very loud and puts out a lot of heat. Over 15 minutes of Cindy driving at different RPM, including up a 6 mile climb out of Phoenix, I with naked ear, stethoscope, and just a long piece of PVC pressed against everything and my ear did not identify a specific source of sound.
Chuck may have called it, about sounds traveling.
With bed down, the 'whine' is not real loud, and has been around for several years. It does not seem to be getting louder. So I am now going to assume that it is just another engine sound.
Because of the higher pitch, it may be coming from turbo as it spins very fast. We do have very good boost up to 27 psi and great performance, including our new fuel pressure gauge, showing 27 psi on long down mountain grades with retarder and 5 gear, and 10 psi with strong uphill throttle. So it seems that waiting for now may be the best approach.
Other turning things, like alternator, dash A/C compressor (thanks Richard) & compressor do not seem to be the source..
I will keep an ear out for changes as we drive about this summer. And will let you know if we find anything.
Thanks to all who helped us, including driving with a window open.
Since we replaced carpet with vinyl tile, we can hear the turbocharger whine when we are traveling at low speeds. It is definitely easier to hear the whine from the passenger seat than from the driver seat. We have the C8.3 engine in a 1997 36' coach.
That type sound can be from many items, so do not over look the hydraulic pump, alternator, idler on a belt tensioner, mechanical fuel pump, of course the turbo just to name a few.
My vote goes with Dave M.
If a bearing is going away, they (on occasion) whine.
Check your idler, alternator & fan pulley. If they don't spin freely, it would be good a good time to replace bearings.
Probably the easiest items on the 8.3L to trouble shoot FWIW. pc
A further check on the automatic belt tensioner:
They can fail in terms of bearing failure and/or dampening.
Watch this Gates Corp video:
http://www.youtube.com/watch?v=uTLV5IU_IMM
Hydraulic pump for power steering would be something to check out.
Cindy commented that maybe we are hearing a turbo whine inside the coach because we covered the great original foam-lead soundproofing with two-sided foil Cool It Thermo Tec, Thermo Guard insulation.
The new foil surfaces may reduce the engine sound deadening that we have benefited from for so many years. The original soundproofing is still in place, but now covered by Thermo Tec.
I got rid of the foam-lead; replaced with fiberglass duct board and a layer of EZ Cool. Definitely not any louder, maybe a little quieter and cooler in the bedroom. I don't hear any whines, but I don't hear very well even with aids. My other half with good hearing hasn't mentioned any noises.