747Flyer Posted November 22, 2021 Report Share Posted November 22, 2021 I have a 1998 Volvo 610. It is the first and only HDT I have owned. Is there some type of valve that is supposed to prevent the suspension air bags from deflating when the truck's air system leaks down over time? I have been putting a jack stand under the rear frame when I plan to park the truck for a few days, as I simply don't like the way it looks sitting there when it squats after the air system has leaked down. Assuming there is not a leak in the bags themselves, should they remain inflated (check valve??) even when the air system has leaked to zero? My truck has a Trailer Saver hitch installed and the gauge for it indicates that it retains air pressure even when the truck's air system has leaked down - this is what set me to wondering if the suspension air bags should do the same. Quote Link to comment Share on other sites More sharing options...
Case20hp Posted November 22, 2021 Report Share Posted November 22, 2021 It’s most likely leaking from the leveling valve. With the movement of the suspension they tend to be the first spot to leak. Quote Link to comment Share on other sites More sharing options...
Jim & Wilma Posted November 22, 2021 Report Share Posted November 22, 2021 The leveling valve is between the air source and bags and will only exhaust air when the deck height rises above the set point as would happen when the load is removed. Otherwise, in my perfect world, rear suspension air pressure should the same “forever” if the load doesn’t change. Possible leak sources are the leveling valve, air lines and fitting and the bags. Our truck suspension will hold for 3 or 4 days or so and the air bags and leveling valve are relatively new. Quote Jim & Wilma 2006 Travel Supreme 36RLQSO 2009 Volvo VNL730, D13, I-shift, ET, Herrin Hauler bed, "Ruby" 2017 Smart Class of 2017 Link to comment Share on other sites More sharing options...
Ray,IN Posted November 22, 2021 Report Share Posted November 22, 2021 (edited) Only speaking of the air suspension on my Spartan mountain master MH chassis. Like Case said leveling valve, or dump valve switch, height control valve are the most likely places. ref: https://www.volvotrucks.us/-/media/vtna/files/shared/body-builder/manuals/volvo_section-6-suspension-and-steering.pdf/ page 45 and up. Don't shoot me for trying to help. Edited November 22, 2021 by Ray,IN Quote 2000 Winnebago Ultimate Freedom USQ40JD, ISC 8.3 Cummins 350, Spartan MM Chassis. USA IN 1SG retired;Good Sam Life member,FMCA ." And so, my fellow Americans: ask not what your country can do for you--ask what you can do for your country. John F. Kennedy 20 Jan 1961 Link to comment Share on other sites More sharing options...
747Flyer Posted November 22, 2021 Author Report Share Posted November 22, 2021 3 minutes ago, Jim & Wilma said: The leveling valve is between the air source and bags and will only exhaust air when the deck height rises above the set point as would happen when the load is removed. Otherwise, in my perfect world, rear suspension air pressure should the same “forever” if the load doesn’t change. Possible leak sources are the leveling valve, air lines and fitting and the bags. Our truck suspension will hold for 3 or 4 days or so and the air bags and leveling valve are relatively new. I'm confused ( happens a lot, LOL) by your response. You stated that the bags should hold basically forever, but then say that your suspension will hold for 3 or 4 days. Is the latter fairly normal? That's about what mine does. If parked longer without being started, it squats. Should I throw money at it, or again is this about normal for these trucks? Thanks. Quote Link to comment Share on other sites More sharing options...
747Flyer Posted November 22, 2021 Author Report Share Posted November 22, 2021 10 minutes ago, Ray,IN said: Only speaking of the air suspension on my Spartan mountain master MH chassis. Like Case said leveling valve, or dump valve switch, height control valve are the most likely places. ref: https://www.volvotrucks.us/-/media/vtna/files/shared/body-builder/manuals/volvo_section-6-suspension-and-steering.pdf/ page 45 and up. Don't shoot me for trying to help. I appreciate your post! Quote Link to comment Share on other sites More sharing options...
Jim & Wilma Posted November 22, 2021 Report Share Posted November 22, 2021 9 minutes ago, 747Flyer said: Should I throw money at it, or again is this about normal for these trucks? Thanks. There are folks whose truck suspension will leak down overnight and those that, well, stay up for many days. For ours, I’m fine with several days and see no harm in losing the suspension other than it takes a bit longer I suppose to get underway waiting to air up the tanks. Agree with others the leveling valve is a good place to check. If leaking, it’s pretty easy to replace and not a bad preventative maintenance task in any case. Quote Jim & Wilma 2006 Travel Supreme 36RLQSO 2009 Volvo VNL730, D13, I-shift, ET, Herrin Hauler bed, "Ruby" 2017 Smart Class of 2017 Link to comment Share on other sites More sharing options...
747Flyer Posted November 22, 2021 Author Report Share Posted November 22, 2021 1 minute ago, Jim & Wilma said: There are folks whose truck suspension will leak down overnight and those that, well, stay up for many days. For ours, I’m fine with several days and see no harm in losing the suspension other than it takes a bit longer I suppose to get underway waiting to air up the tanks. Agree with others the leveling valve is a good place to check. If leaking, it’s pretty easy to replace and not a bad preventative maintenance task in any case. 👍👍 Quote Link to comment Share on other sites More sharing options...
lappir Posted November 22, 2021 Report Share Posted November 22, 2021 The older trucks have air leaks. It's a given, you can chase them with the "Whisper" thingy, I think SuiteSuccess had one at the ECR the year I attended and many people tried to find their leaks. I've owned my truck for over 10 years I think and from day one it wouldn't keep air in the bags. Recently it's gotten better, but I have no idea why. Letting the truck run long enough to build up air pressure is the time you should be doing your pre trip evaluation. Mine is usually done before I'm ready to put it in gear. If yours is taking too long it might be more important to check out the compressor. Insomnia is why I'm here at this hour. It may have affected my response, but I don't think so. Rod Quote White 2000/2010Volvo VNL 770 with 7' Drom box with opposing doors, JOST slider hitch. 600 HP Cummins Signature 18 Speed three pedal auto shift. 1999 Isuzu VehiCross retired to a sticks and bricks garage. Brought out of storage the summer of 2022 2022 Jeep Wrangler Sport S Two door hard top. 2007 Honda GL 1800 2013 Space Craft Mfg S420 Custom built Toyhauler The Gold Volvo is still running and being emptied in July. Link to comment Share on other sites More sharing options...
phoenix2013 Posted November 22, 2021 Report Share Posted November 22, 2021 9 hours ago, 747Flyer said: I have a 1998 Volvo 610. It is the first and only HDT I have owned. Is there some type of valve that is supposed to prevent the suspension air bags from deflating when the truck's air system leaks down over time? I have been putting a jack stand under the rear frame when I plan to park the truck for a few days, as I simply don't like the way it looks sitting there when it squats after the air system has leaked down. Assuming there is not a leak in the bags themselves, should they remain inflated (check valve??) even when the air system has leaked to zero? My truck has a Trailer Saver hitch installed and the gauge for it indicates that it retains air pressure even when the truck's air system has leaked down - this is what set me to wondering if the suspension air bags should do the same. 747Flyer, with a truck up there in "truck years" chasing air leaks can turn into a full time "hobby". I would venture an opinion that your 21 year old truck is equal to 80 human years, an age when controlling flatulence becomes a problem. In more technical terms air lines become very hard and brittle after just few years in service, as do the O-rings and gaskets in the air fitting. My truck was 5 years old when I bought it and 15 years old when I got rid of it. If I got 3 day before it squatted all the way down, I was happy. Lot's of airlines and fittings to chase. Quote Link to comment Share on other sites More sharing options...
Parrformance Posted November 22, 2021 Report Share Posted November 22, 2021 1 hour ago, phoenix2013 said: 747Flyer, with a truck up there in "truck years" chasing air leaks can turn into a full time "hobby". I would venture an opinion that your 21 year old truck is equal to 80 human years, an age when controlling flatulence becomes a problem. In more technical terms air lines become very hard and brittle after just few years in service, as do the O-rings and gaskets in the air fitting. My truck was 5 years old when I bought it and 15 years old when I got rid of it. If I got 3 day before it squatted all the way down, I was happy. Lot's of airlines and fittings to chase. A gassy horse will never tire A gassy man is a man to hire🤣 Quote 2006 Volvo VNL 780, " Arvey" Volvo D12, 465hp, 1650 ft/lbs tq., ultrashift 2003 Jeep Wrangler Rubicon 2010 Forest River Coachman Freedom Express 280RLS Jackalopee Link to comment Share on other sites More sharing options...
Darryl&Rita Posted November 23, 2021 Report Share Posted November 23, 2021 Be aware that the levelling valve can have internal and external leaks. External leaks are the kinds that leak bubbles or the "Whisper" can detect, and are just like they sound. Air pressure leaks to the atmosphere. Internal leaks are trickier. The truck pressure can drop, through separate leaks, while the suspension levelling valve will try to donate air to the system, to keep it pressurized. This is not how they are intended to work, but it does happen with wear. This is often too slow of a leak for even a "Whisper" to detect. Quote 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 QuantumPlease e-mail us here. Link to comment Share on other sites More sharing options...
Lance A Lott Posted November 23, 2021 Report Share Posted November 23, 2021 I would be ecstatic if mine stayed up 1 hour, and I mean the entire system not the rear bags, I have to let the truck air up if I stop for lunch. Quote Link to comment Share on other sites More sharing options...
phoenix2013 Posted November 23, 2021 Report Share Posted November 23, 2021 (edited) Here's another reason why this can turn into "fools errand" on senior citizen trucks. As I mentioned above the air lines stiffen with age, the reason, the material (plastic) from which they are made is hygroscopic, meaning, it absorbs water from the air. It's that absorption that turns it from nice and pliable to stiff and brittle. Combined with quick connect (push in and seal) air fittings this is great for building trucks air systems quickly and efficiently. It also works well for years. So why do old trucks develop flatulence? New trucks; soft and pliable line plus engine and road vibration, no problem, Old trucks; stiff and brittle lines plus engine and road vibration, flatulence. You can get away (sometimes) replacing the air fitting where the leak is, with old lines using a new quick connect fitting might not solve the problem, using a "real" DOT brass fitting is a better choice, you can crank them hard enough to stop the leak even on old stiff lines. Edited November 23, 2021 by phoenix2013 Quote Link to comment Share on other sites More sharing options...
Wrknrvr Posted November 23, 2021 Report Share Posted November 23, 2021 (edited) You may want to look on youtube for a Infineon air leak detector. Years ago it was on the forum about them and several of us on the forum purchased one. I have one and in two weeks or so I will be using it on our truck as it is leaking down in a day now. Hopefully someone on the forum may have a picture of one. Ours is in hiding at this moment or I would post a picture of it. I could not find it in the resource guide. With a quick search. Vern Edited November 23, 2021 by Wrknrvr Quote Link to comment Share on other sites More sharing options...
Darryl&Rita Posted November 23, 2021 Report Share Posted November 23, 2021 Infinicon Whisper on Amazon. Quote 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 QuantumPlease e-mail us here. Link to comment Share on other sites More sharing options...
GlennWest Posted November 23, 2021 Report Share Posted November 23, 2021 (edited) I have one and not had much luck with it. But it is usually windy when I use it. Think it work well in a shop Edited November 23, 2021 by GlennWest Quote 2003 Teton Grand Freedom towed with 2006 Freightliner Century 120 across the beautiful USA welding pipe.https://photos.app.goo.gl/O32ZjgzSzgK7LAyt1 Link to comment Share on other sites More sharing options...
Wrknrvr Posted November 23, 2021 Report Share Posted November 23, 2021 Thanks for the correction Darryl. my mind was on my own project today. I does work rather good. It may need a better head phone set. But I have found some small air leaks that would have been all but impossible to find without it. Vern Quote Link to comment Share on other sites More sharing options...
rpsinc Posted November 23, 2021 Report Share Posted November 23, 2021 I am outfitting my 730 with a hose quick connect to air up things but I also made an adapter to allow the male quick connect to allow me to use my small compressor so that I can fill the air system without having the truck running. I also use kids bubbles as my leak detector of choice. Quote Marcel Link to comment Share on other sites More sharing options...
Parrformance Posted November 23, 2021 Report Share Posted November 23, 2021 8 hours ago, Lance A Lott said: I would be ecstatic if mine stayed up 1 hour, and I mean the entire system not the rear bags, I have to let the truck air up if I stop for lunch. Took me several weekends to fix the one hour air down. Find a leak fix it Find a leak fix it Find a leak fix it And so on........ Quote 2006 Volvo VNL 780, " Arvey" Volvo D12, 465hp, 1650 ft/lbs tq., ultrashift 2003 Jeep Wrangler Rubicon 2010 Forest River Coachman Freedom Express 280RLS Jackalopee Link to comment Share on other sites More sharing options...
jenandjon Posted November 24, 2021 Report Share Posted November 24, 2021 They all leak. You will drive yourselves crazy fixing every little thing. Dont sweat the small stuff. Quote Farmer, Trucker, Equipment operator, Mechanic Quando omni flunkus moritati-When all else fails, play dead I'm a man, but I can change, if I have to, I guess. Link to comment Share on other sites More sharing options...
747Flyer Posted November 25, 2021 Author Report Share Posted November 25, 2021 On 11/23/2021 at 10:14 AM, Wrknrvr said: You may want to look on youtube for a Infineon air leak detector. Years ago it was on the forum about them and several of us on the forum purchased one. I have one and in two weeks or so I will be using it on our truck as it is leaking down in a day now. Hopefully someone on the forum may have a picture of one. Ours is in hiding at this moment or I would post a picture of it. I could not find it in the resource guide. With a quick search. Vern I have one. Thanks. Quote Link to comment Share on other sites More sharing options...
beemergary Posted November 28, 2021 Report Share Posted November 28, 2021 Hello My 1984 Peterbilt 359 suspension is usually good for "2" Months even in cold weather. The other air is good for "1" week. It has way more places for leaks-even has air wipers than newer trucks. They used rubber lines with flare fittings. Bought some new seats and they go down in a week were the old Peterbilts never did. They got plastic lines with push-loc fittings Quote Link to comment Share on other sites More sharing options...
Star Dreamer Posted December 2, 2021 Report Share Posted December 2, 2021 One item to be aware of, at least on our Freightliner, that as the suspension drops, the truck will move slightly. Be careful that it does not fall off or tilt the jack stands when it does. Ours will lose some air overnight to the point the suspension drops, but it varies based on air temperature. The warmer it is the slower it runs low on air. Typically, if I am not going to unhook for an overnight stop, I manually drop the rear suspension using the dash switch (I have to do it a couple times as my switch automatically defaults to the up location and so it airs back up the suspension when you take your figure off of it. This way I don't have to hear it bang when it lets the air out itself in the middle of the night. Quote 2005 Freightliner Century S/T, Singled, Air ride ET Jr. hitch 2019 46'+ Dune Sport Man Cave custom 5th wheel toy hauler Owner of the 1978 Custom Van "Star Dreamer" which might be seen at a local car show near you! Check out http://www.hhrvresource.com/ for much more info on HDT's. Link to comment Share on other sites More sharing options...
Parrformance Posted December 2, 2021 Report Share Posted December 2, 2021 When the air leaks got so bad as to drop the suspension during a 1 hour stop for dinner while traveling, I decided to fix it. I aired up the truck st the Schrader port on the governor, I grabbed a large bottle of kids bubble mix. I poured it in a spray bottle started at the rear most air bags, and sprayed every air line connection. I worked forward fixing or replacing any component that made bubbles. The Truck will stay up for weeks, and has not "folded" the big bags in the rear even after sitting over a month. Quote 2006 Volvo VNL 780, " Arvey" Volvo D12, 465hp, 1650 ft/lbs tq., ultrashift 2003 Jeep Wrangler Rubicon 2010 Forest River Coachman Freedom Express 280RLS Jackalopee Link to comment Share on other sites More sharing options...
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