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Strange Issue with Compressor


bmzero

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I was driving my truck/trailer back from a MX race yesterday evening. As I pulled away from stopping at a stop sign, I heard a large popping sound from the engine bay and a sudden sound of escaping air. Clearly it was an air line of some sort because boost pressure and temperature remained constant. Soon, the pressure gauges started telling the story of air loss.

 

I was very close to home (about 4 miles), so I decided to try and make it home before it reached critical air pressure levels. I made it all but a half mile from my house when the Volvo computer started calling me bad names and made me pull over.

 

After searching air lines for about 5 minutes, I noticed that the main feed (~3/4" metal tube) exiting the compressor had come loose. I thought that seemed a little strange, but my hope was that I could put it back in, re-tighten the compression fitting and I would be back on my way. It turned out to not be that easy. I put the tube back in, tightened the heck out of it and cranked the engine. Immediately it blew the tube out of the compressor. Then, I cleaned both sides of the fitting and tried again. Same result, but this time, I realized that the fitting was not, at all, getting tight on the tube.

 

Then, Marine Corps mode kicked in. It was time to adapt and overcome. I put the tube back into the compressor and ratchet-strapped it secure. This held the line into the compressor well, but still allowed a pretty big air leak. However, it was enough to get the truck and trailer the rest of the way home.

 

After more thought, that might not be a compression fitting at all, but maybe the nut is built onto the tube and there should be a flange (double the wall thickness for about a half inch) at the end of the tube that is now inside of the fitting still attached to the compressor. This would explain why the fitting being tight did not retain the tube.

 

Has anyone here ever heard of this issue?

 

I haven't be able to find a parts diagram for the D16 that would confirm my suspicion about the fitting. I will call Volvo only as a last resort.

"Willy Mammoth" - Volvo 730, Sold

Heartland Cyclone 4000 Toy Hauler
T-Minus 26 years and counting to being a full timer.

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Thanks for the feedback.

 

I replaced the entire dryer assembly (and filter) about 50 miles prior to this trip. It seems an odd coincidence, for sure. I replaced the dryer because the air system seemed to purge more than I thought was necessary. I can't tell that it helped much.

 

I called Volvo this morning and talked to them about it. He says there should definitely be a ferrule on the end of the hard line. On mine, it is completely smooth and the tube will slide into and out of the compressor even with the capture nut very tight. He said his diagrams weren't conclusive on what the end of the tube was supposed to look like (ie. just a flair on the end or a section of double-wall tube), so I'm going to pull the nut off and see if there's a piece of tube (that would have been the double-wall section) still stuck in there. If there is a piece of tube behind the capture nut, I'll remove it and reattach it, permanently, to the tube.

 

Unfortunately, that piece of tube is $360 from Volvo, so I want to make sure that's really what I need before ordering.

 

I can't help but think there is another issue going on with the air system, though. Any ideas? How is the pressure regulated other than the purge?

 

Does anyone have a link to good parts diagrams for the Volvo engines? I wasn't able to find any through search or the Google.

 

I did see this diagram set, but it does not apply to the D16.

"Willy Mammoth" - Volvo 730, Sold

Heartland Cyclone 4000 Toy Hauler
T-Minus 26 years and counting to being a full timer.

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Your air pressure is controlled by the air governor which it generally bolted to the compressor. They usually look something like this: 275491P.jpg

 

Thanks.

 

Is it possible that the governor is bad causing excess pressure?

"Willy Mammoth" - Volvo 730, Sold

Heartland Cyclone 4000 Toy Hauler
T-Minus 26 years and counting to being a full timer.

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Excess pressure will only trip the PSV on the tanks, not blow tubing out of a ferrule. At some point, that nut was loosened off, and the pressure pushed the tubing out. Replace the ferrule set, and drive away. I don't know what manufacturer Volvo uses, but I can almost guarantee that it's not an in-house Volvo part.

I have been wrong before, I'll probably be wrong again. 

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Excess pressure will only trip the PSV on the tanks, not blow tubing out of a ferrule. At some point, that nut was loosened off, and the pressure pushed the tubing out. Replace the ferrule set, and drive away. I don't know what manufacturer Volvo uses, but I can almost guarantee that it's not an in-house Volvo part.

 

That was my thought, as well, but it would be convenient to find a root cause, if one exists.

 

Without a doubt, the nut was not loose. It took a 24" adjustable wrench to break it loose, with me standing in the engine bay. However, I think you're right that the tube/ferrule assembly broke somehow. I suspect that the ferrule on the end of the tube was a larger ID tube fixed onto the inner tube and that larger ID tube simply came loose from the inner tube allowing the inner tube to slide out. That's just a guess at this point, though, but that does explain all of the symptoms.

"Willy Mammoth" - Volvo 730, Sold

Heartland Cyclone 4000 Toy Hauler
T-Minus 26 years and counting to being a full timer.

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Although this is a Volvo engine to Volvo chassis connection, it is one of those grey areas in truck manufacturing. The engines are shipped with a plug at that point and someone(chassis engineer) in Greensboro decides what method is used to connect to the air system. Because of different chassis configuations different fittings get used, sometimes according to what happens to be on the shelf when the truck was assembled. They probably discovered that some sort of flexible hose would be better, maybe later serial #'s have that upgrade. This sounds like it gave it up because of vibration. There is a lot of heat on that section of pipe, compressed air is probably over 250 degrees at that point, and a lot of expansion and contraction occurs right there in normal service.

Jeff Beyer temporarily retired from Trailer Transit
2000 Freightliner Argosy Cabover
2008 Work and Play 34FK
Homebase NW Indiana, no longer full time

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This sounds like it gave it up because of vibration. There is a lot of heat on that section of pipe, compressed air is probably over 250 degrees at that point, and a lot of expansion and contraction occurs right there in normal service.

 

I think you're probably right about that.

"Willy Mammoth" - Volvo 730, Sold

Heartland Cyclone 4000 Toy Hauler
T-Minus 26 years and counting to being a full timer.

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Bmzero, what does the end of the tube look like? Is it straight and square like a machine cut or does it look like it has cracked?

 

It's straight and square. There didn't appear to be any damage to it. That's why I think the tube and the ferrule are now two pieces that were supposed to be one piece.

"Willy Mammoth" - Volvo 730, Sold

Heartland Cyclone 4000 Toy Hauler
T-Minus 26 years and counting to being a full timer.

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We want pictures when you pull the nut off again to look in the hole. I think you will find your answer there. I know you will engineer it better than new.

Ron C.

2013 Dynamax Trilogy 3850 D3

2000 Kenworth T2000 Optimus Prime

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I'd recommend replacing the governor if/when you replace the dryer assembly. While it may not be necessary, the part costs about $20. Better safe than sorry....lose a governor, you are not moving.

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I'd recommend replacing the governor if/when you replace the dryer assembly. While it may not be necessary, the part costs about $20. Better safe than sorry....lose a governor, you are not moving.

 

Thanks, Jack. That's a cheap insurance policy, for sure.

 

I'll add some photos.

"Willy Mammoth" - Volvo 730, Sold

Heartland Cyclone 4000 Toy Hauler
T-Minus 26 years and counting to being a full timer.

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I hit the wrenches at about 4 o'clock this morning to try and knock this out before work. It's great to get covered from head to toe in grease before heading in to the office. When I came in to the house, my son said I looked like a coal miner.

 

That being said, I was finally able to get the feed line off of the truck. If this ever happens again, I'm just going to sell the truck as-is. The connection between the hard line and the soft line that feeds the tanks is right behind the engine, almost impossible to get to. At one point I was literally squeezed between the frame rails and the floorboard of the truck. I can clearly say I have no claustrophobia now.

 

As I suspected, it seems the ferrule separated from the tube. As you can see in the photo below, the shiny piece (ferrule), should be attached to the end of the tube. It was left inside of the nut when I removed the fittings. Seeing that both pieces are mild steel, I will probably just TIG weld the ferrule back onto the tube. I will not be welding the seal side of the ferrule, so it should still seal as well as it did originally. The TIG weld will never break, which is more than I can say for the OEM part.

 

f72ebcf5-28b4-4d19-8223-9e40ce63c6f7-s.j

"Willy Mammoth" - Volvo 730, Sold

Heartland Cyclone 4000 Toy Hauler
T-Minus 26 years and counting to being a full timer.

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I'd recommend replacing the governor if/when you replace the dryer assembly. While it may not be necessary, the part costs about $20. Better safe than sorry....lose a governor, you are not moving.

 

Jack, I don't have an assembly like pictured above anywhere between the compressor and the dryer. Could the governor be built into the compressor?

"Willy Mammoth" - Volvo 730, Sold

Heartland Cyclone 4000 Toy Hauler
T-Minus 26 years and counting to being a full timer.

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Jack, I don't have an assembly like pictured above anywhere between the compressor and the dryer. Could the governor be built into the compressor?

 

Look on your air tanks for the governor (most are at the front of the tank). That is were some of the newer trucks are placing them.

2017 Kenworth T680
2015 DRV 38RSSA Elite Suites
2016 Smart Prime

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Look on your air tanks for the governor (most are at the front of the tank). That is were some of the newer trucks are placing them.

 

I saw where you said that earlier, but I assumed you meant just near the air tanks. I would have thought the governor needed to be inline prior to the air dryer, but maybe not. I'll look at it more this evening in the day light. Thanks.

"Willy Mammoth" - Volvo 730, Sold

Heartland Cyclone 4000 Toy Hauler
T-Minus 26 years and counting to being a full timer.

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Instead of TIG welding, you could just replace the nut/ferrule set. As I said, "At some time," that nut has been run loose, and vibration wear has been introduced. It matters not a bit that it was 24" wrench tight when it failed. The back surface of the ferrule must be flat and parallel to pull the front face into the sealing face of the fitting properly. TIG welding would still require some machine work to bring back the surfaces. This is a solution looking for a problem.

I have been wrong before, I'll probably be wrong again. 

2000 Kenworth T 2000 w/N-14 and 10 speed Gen1 Autoshift, deck built by Star Fabrication
2006 smart fourtwo cdi cabriolet
2007 32.5' Fleetwood Quantum


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Instead of TIG welding, you could just replace the nut/ferrule set. As I said, "At some time," that nut has been run loose, and vibration wear has been introduced. It matters not a bit that it was 24" wrench tight when it failed. The back surface of the ferrule must be flat and parallel to pull the front face into the sealing face of the fitting properly. TIG welding would still require some machine work to bring back the surfaces. This is a solution looking for a problem.

 

From talking to Volvo, I believe I would have to buy the whole hardline assembly, which would include the ferrule, nut, and line. Maybe I'm missing what you're saying, but from what I took off of the truck, I don't believe this is a typical four-piece compression ferrule setup. There was no "back ferrule" inside of the nut when I removed it. That's why I am thinking the ferrule should be attached to the hard line directly (not using the compression provided by the back ferrule). I'm going to take it to Volvo today and see what they say.

 

I was planning on fusing the ferrule onto the tube. It would most likely not require filler rod. The nut would still make contact with the flat surface of the ferrule to ensure a proper fit. The weld bead would be very faint and only noticeable on the inside radius between the nut and the tube.

"Willy Mammoth" - Volvo 730, Sold

Heartland Cyclone 4000 Toy Hauler
T-Minus 26 years and counting to being a full timer.

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Can't see any manufacturers marks on the fitting or nut, but many make a single piece ferrule. I'd be looking for a Parker store, or similar, and just replace the whole works. This is assuming the end of the tubing is in decent condition.

I have been wrong before, I'll probably be wrong again. 

2000 Kenworth T 2000 w/N-14 and 10 speed Gen1 Autoshift, deck built by Star Fabrication
2006 smart fourtwo cdi cabriolet
2007 32.5' Fleetwood Quantum


Please e-mail us here.

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I took all of the pieces to Volvo. I got a different guy this time than whom I talked to yesterday. He instantly said it was a single piece ferrule and handed me one off of the shelf in about 30 seconds. He said all of the other parts looked good and there would be no concerns reusing them.

 

I also picked up the governor which was just over $11.

 

Reassembly tonight. I can't wait... (definitely sarcasm).

 

Thanks to everyone who shared information. Hopefully this thread can help someone in the future as well. I'll make sure and update the thread with the success story.

"Willy Mammoth" - Volvo 730, Sold

Heartland Cyclone 4000 Toy Hauler
T-Minus 26 years and counting to being a full timer.

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