Community Forums

laheze · 11-30-2015, 12:14 AM

I purchased our 2008 HolidayRambler in June of 2015. I'm still learning about my coach. My airbag and brake system air pump (if they work off the same compressor) seems to knock sorta loudly when running. I can't hear it from the inside but when I start the coach to air up the system before departing a camp out, go outside loading or just looking around it seems like the compressor is rattling/knocking too loud. Is this normal or is there some lubricant missing that I need to know about? Are my piston rods loose? Is this piston driven or a rotary air compressor? Either way it sounds like piston rods loose and knocking. Are these pumps normally a long term item or do they fail often?
Thank You

twinboat · 11-30-2015, 04:52 AM

The compressors are piston pumps that usually last a long time. They are feed engine oil and coolant, so no checking is needed.

If there was a long term air leak causing the compressor to run constantly, it could be worn out.

It could also be the spline coupling failing.

Get an experenced truck mechanic to listen to it. They do make some noise under load and what you hear could be normal.

GreaTOne65 · 11-30-2015, 11:29 AM

What you are hearing is the air dryer, not the compressor. My compressor has only 30,000 miles on it, and it is noisier than the one on my other coach with over 100,000 miles. I wouldn't worry about it unless it won't build air, then it's only a matter of changing the air governor on the compressor, I think the one I bought, was $22.00.

twinboat · 11-30-2015, 12:24 PM

Well, there you have it.
The Great One heard the noise over the internet and says ignore it.
Drive on !

laheze · 11-30-2015, 10:35 PM

Thank you for your replies.
Where is the air Pump? Is it bolted directly to the engine or is it powered by a V belt?

jacwjames · 12-01-2015, 05:36 AM

The compressor is attached directly to the engine and is gear driven. If you are looking from the back of the coach it will be on the right side, it is hard to see. On my ISC engine it is under the AC Compressor.

If you want to educate yourself on the engine join the Cummins Quickserve site, it is free, register and then input your engine serial number.
https://quickserve.cummins.com/info/index.html
Once on the site you can query any type of part. There are general schematics on the engine and each component.

Normally you do not actually hear the compressor since the engine noise overwhelms it. Chances are if it is making good air pressure it is probably OK.

GreaTOne65 · 12-01-2015, 10:29 AM

Thank you twinboat, it really helps to have a critique waiting for a chance to berate one's responses. If he was familiar with his coach he would know where the air dryer is, and would know it is the air dryer that is making the noise, not the compressor. In the 60 yrs. I worked on and drove trucks, NEVER EVER LOST A COMPRESSOR. If his vehicle will build air, 99.9 chances it's the air dryer making the noise.

twinboat · 12-01-2015, 10:43 AM

He bought it in June, maybe not to familiar with it. Probable don't have 60 years on the road either.

Been fixing them for 45 years, changed 2 for failed splines. Fixed the noise we were hearing and the steel in the oil samples.

Changed a few that were blowing oil into the air system.

Enjoy

laheze · 12-01-2015, 11:32 PM

Thank you all again. I really appreciate your help.
I thought the noise seemed more loud on the passengers side when that sorta loud knocking noise is going on before the compressor reaches its 115 to 120 psi and relieves itself.
I am slowly coming up to speed on my first coach. I've owned only front engine gas powered motor homes in years past plus several 5th wheels. I've driven Ford F250s since 1985 and currently a2012 model, so I'm used to that type of Diesel engine driving. These coaches are just plain ole big! I normally can take care of problems mostly on my own. If I have a broken whatever I fix it myself usually. When I was at the dealer looking at this thing, I thought it might just be too big and heavy for me to mess with, just pay someone and let them do it. I am trying to gear my brain back to me doing things myself like I've always done. I'll see how things progress in the do it myself category. When I fix things I do not take shortcuts or the cheap way out, I do it correctly. I've seen a lot of slipshod work in my life and that kind of repairs usually bites somebody in the backside when they least expect it.

So I've got another question. Where is the dryer your talking about? What is it? Is it built into the air Pump? How big is it? How expensive are they? Are they easy to repair/replace?
How does a dryer make noise?
I've owned electric dryers before that were used for removing water from my big air compressor and airlines. It reminded me of a window air conditioner and was about the same size.
Thank you, all information is appreciated.

GreaTOne65 · 12-02-2015, 09:26 AM

Larry, the air dryer on my Beaver is on the passenger side clear in the back corner compartment. I replaced mine in September, because it had never had the filter changed and it had quit working. The pump, usually makes no noise, but the dryer will make a hammering sound, it is normal, and after it gets up to pressure it will release air, makes a whooshing sound then starts all over, when it gets up to pressure and if there is no moisture present it will not make the sound. If you want to know about the air dryer, Google it. Google is a wonderful tool, it knows everything! LOL!!

laheze · 12-02-2015, 04:39 PM

The pump, usually makes no noise, but the dryer will make a hammering sound, it is normal,
If you want to know about the air dryer, Google it. Google is a wonderful tool, it knows everything! LOL!![/QUOTE]

Thank you Greatone65,

The HAMMERING NOISE describes what I was hearing and I thought it sounded like the piston rods were coming unbolted. If the hammering noise is normal then I won't worry about it. I guess I'll learn why the dryer is so loud, it sounds like it's looking for some concrete to breakup!

palehorse89 · 12-02-2015, 04:54 PM

On a trip, I lost my power steering, .......oil streak behind me.........air compressors crankshaft broke in two, knocked the large soft plug out of the bottom of the compressor, and then the oil poured out. What a mess. The reason for the steering loss, is that the compressor is bolted to the back side if the timing cover and is driven by helical gears, and then the power steering pump is bolted onto the rear of the compressor. I would suggest have someone that understands these Cummins engines( or any good diesel mechanic) take a look at yours.
Mine was replaced under a recall while the first owner had it, then it failed some years later on me.
A hammering noise is not normal. I can hear my compressor load and unload through the air intake up on the rear of the Coach if I am back there, and of course when the air dryer spits. My air dryer and all others I have ever been around, never hammer, it is not in their nature to hammer, they are a moisture ejector simply.

palehorse89 · 12-02-2015, 05:04 PM

Quote:

Originally Posted by GreaTOne65

Larry, the air dryer on my Beaver is on the passenger side clear in the back corner compartment. I replaced mine in September, because it had never had the filter changed and it had quit working. The pump, usually makes no noise, but the dryer will make a hammering sound, it is normal, and after it gets up to pressure it will release air, makes a whooshing sound then starts all over, when it gets up to pressure and if there is no moisture present it will not make the sound. If you want to know about the air dryer, Google it. Google is a wonderful tool, it knows everything! LOL!!

Google is a wonderful tool for sure, I learned about them from my truck driving days. When a diesels compressor gets a signal to load and make air, it does. When it reaches its set point of app. 125 lbs. a signal is sent, it "Unloads" and the air dryer spits. the compressor will not load up again till it gets a lower air signal (Cut in pressure) and the dryer will not purge again till the compressor loads and reaches set point. (Cut out pressure) They also do not sense moisture, they eject it from a collection point in the dryer. All the compressed air flows through the desiccant filter for drying.
Some good reading/studying here http://www.anythingtruck.com/htp-bra...ad9-works.html