Seneca - Air Leak after Shutdown

[SuddenRush]

Hello all, long time no see.

Unfortunately, my wife and I haven't been using our 2015 Seneca too much this summer, just short trips here and there back and forth to the race track.

This weekend however, we ventured about 150 miles to a race out of town. Trip down was easy, albeit over rough roads. However, when we got home, and I got our Seneca parked, I noticed an air leak sound coming from under the RV while I was hooking up shore power.

I am still fairly unfamiliar with all the systems on this thing, but I have never heard an air leak like this after shut down. We got home late, and had to get to work early, so I quickly looked underneath and tracked down where the sound was coming from.

Under the driver side, near the exhaust, there appears to be an air tank there. Out of the back of the tank there appears to be some sort of relief valve, and the cover on it says something like "pull pin to manually drain". I don't see a pin. In the middle there was a manufactured hole (orange-ish in color) that when I put my finger over it, stopped the leak. There didn't appear to be anyway to stop the leak otherwise. It was dark and very late, so I didn't think to take a picture.

I know the system leaks air, as the rear suspension is always low after sitting for a couple days, but I've never actually heard it leak when sitting stagnant and stationary. Jacks were up (I wasn't dumping the air on purpose).

Any ideas? Thanks in advance.

[che57vy]

I do not have a Seneca but on my diesel work truck with air brakes that is a valve to manually drain moisture that collects in storage tank, mine has a automatic valve some times debris gets in seat of valve I manually blow it off and it reseats itself no more leak

[sdwelling]

Originally Posted by SuddenRush

Hello all, long time no see.

Unfortunately, my wife and I haven't been using our 2015 Seneca too much this summer, just short trips here and there back and forth to the race track.

This weekend however, we ventured about 150 miles to a race out of town. Trip down was easy, albeit over rough roads. However, when we got home, and I got our Seneca parked, I noticed an air leak sound coming from under the RV while I was hooking up shore power.

I am still fairly unfamiliar with all the systems on this thing, but I have never heard an air leak like this after shut down. We got home late, and had to get to work early, so I quickly looked underneath and tracked down where the sound was coming from.

Under the driver side, near the exhaust, there appears to be an air tank there. Out of the back of the tank there appears to be some sort of relief valve, and the cover on it says something like "pull pin to manually drain". I don't see a pin. In the middle there was a manufactured hole (orange-ish in color) that when I put my finger over it, stopped the leak. There didn't appear to be anyway to stop the leak otherwise. It was dark and very late, so I didn't think to take a picture.

I know the system leaks air, as the rear suspension is always low after sitting for a couple days, but I've never actually heard it leak when sitting stagnant and stationary. Jacks were up (I wasn't dumping the air on purpose).

Any ideas? Thanks in advance.

I don't know the Seneca, however, all air tanks have drain ports at the lowest point to remove water. This sounds like what you have - minus the pin in the center of the circular hole. I have replaced this drain port in my workshop air compressor tank.

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[Dustdevil]

Air tank construction is governed usually by ASME. If that is the case for a DOT system like the Seneca, it undoubtedly has a pressure relief valve. From your description, sounds like that is the device that is leaking, not sure. Pictures would probably help. The purpose is to ensure the tank never sees pressure beyond its design limitations. Sometimes these valves get a bit of crud in the seat and leak. Sometimes the pressure sensor in the system isn't working correctly, and the compressor keeps pumping past the pre-set limit to shut off, and the relief valve opens to ensure proper limits. Sometimes the relief valve just fails. I'd check your pressure sensor for compressor shut-off and your pressure relief valve for the problem.

[RyRoRyan]

On the senecas, because we dont have air dryers, we have automatic drain valves..(you can even have these if you have a dryer). It sounds like you are describing one of these valves. These open and close automatically as the pressure changes in the tank to release the water from building in the tank. It sounds like yours may be faulty or stuck. You can try to push on the pin (its the little shrader valve looking thing right in the middle of the unit) and see if that releases any air/water and see if it closes back up correctly once you do that. You will need some pressure in the system when you do this, as the valve will basically do nothing with no pressure. If that does not stop it leaking then you need to replace it, or have it replaced if somehow still under warranty. If I am correct I think the part is Bendix DV-2 automatic tank drain valve.

[ed4ster]

Here's a picture of the auto moisture drain valve SuddenRush is talking about. I have not had any leakage issues to speak of. But thinking about having an air dryer installed on our rig since we live in northern "very humid" Alabama.

ed

[memphis02]

I have had issues with that valve. I actually thought it was the cause of an issue that turned out to be the pressure switch, in the dash. I attempted to purge the tank using the needle and it stuck open momentarily. I ended up draining about a pint of water (and rust) out of the system and ever since, my air alarm goes off within 5-10 sec of starting whereas before it would stay on significantly longer. -I try to purge every time I put the rig up for more than a week or two between trips, now.

[Mountain Cajun]

That exact valve caused me to have to replace my air compressor. (Under warranty from Cummins) Freightliner replaced it with a manual cable for me to pull once or twice a day. They were shocked Jayco didn't put air dryers. They said valve in question is junk!


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[ed4ster]

Mountain Cajun next Monday I have an appointment with our local Freightliner service center to get an estimate on having them install a air dryer on our Seneca. Hopefully it won't be too painful.

A side note we have not had any problems with the auto valves sticking from debris (rust flakes). Every time I have pressed on the little pin just air would hiss with no water. We live in northern AL. with high humidity, I would have thought we would be seeing lots of water come out like on my shop air compressor.

ed

[Mountain Cajun]

Mine rusted up probably because I spend winters in Louisiana. I have 25,000 miles on mine. I just pi$$e$ me off that Jayco wouldn't spend the extra money to put dryers on all Senecas from the factory. They know we spent a lot of money on these rigs, and we'll keep them for a long time. Wish I knew now what I didn't know then! Ok, rant over!


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[Mountain Cajun]

Now that my bp is back down, let us know how much it's going to be ed4ster, I'm thinking about $1700!


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[SuddenRush]

Thanks for all the replies.

I climbed back under last night after work, and the pin was indeed stuck. I pressed it in and it easily reset itself with minimal issue.

However, I did notice that orange color is all rust (something I didnt notice the night before, I thought it was paint). So now I am concerned that my tank is rusting from the inside out.

I live in Southern MD, which is very humid during the summer. I also make a lot of short trips several times a month, which I guess could be adding more moisture to the system due to the constant on/off of the compressor.

I didn't know this should be a normal maintenance thing.. now I do. I will be bleeding off the air after each trip home to hopefully get rid of any moisture in the tank.

Is there something more to it? Has anyone installed a drain, similar to what's found on an air compressor. I don't have money to install a dryer, first kid will be here in 2 months... but I can't have my RV rotting from the inside out. Any ideas.

Thanks again... this forum is a repeatable life saver for me.

[javamon]

Here's the Bendix documentation that gives lots of detail on how the valve works, etc. It is designed to open up and purge air whenever there is a 2 psi or greater reduction in air pressure (ie. stepping on your brake). I remember my Freightliner mechanic warning me that many Freightliner problems/issues are caused by lack of use.

Tried uploading pdf, but it must be too large. Here's a link:

http://www.plazafleetparts.com/uploa...stallation.pdf

[Dustdevil]

Compressed air systems often produce large amounts of condensed water inside the pressure vessel. You're compressing and heating atmospheric air and putting it in a tank. The compression tends to condense vapor, but the heat you add to the air tends to keep it in vapor form, and overrides the compression effects. Until it hits the tank, where it cools. That air which compresses to approximately 1/7 its original volume still contains the same amount of water, because water doesn't compress and hydrogen and oxygen molecules don't disappear. So, it would have up to 7X the relative humidity when the air cools to its original pre-compressed temperature, if that is possible. It's not. So, the tank is a host to massive condensation of water vapor into liquid water. That's what this device is designed to vent back to atmosphere outside the tank. It does so, but keep in mind this liquid water also rusts the interior of the tank. So, this valve must also deal with the rust, and the resulting oily film resulting from the compression of smoggy air (air with hydrocarbons and other contaminants). It's a witches brew of nastiness, especially if the compressor is oil lubricated (I don't know about this compressor in particular).

The reason dryers are used at the compression stage is to try to lower the relative humidity of the newly-compressed air before it enters the tank, so it can't rust the interior and foul all the components downstream. Dryers are often used after the tank to protect all the components the compressed air must supply and operate, which also see the witches brew with the air. This drain valve handles the worst of it, I'm sure. But every time compressed air goes downstream, some of what's in that tank goes with it. Filtration and drying components are good, but they are expensive. The effects of this stuff is cumulative. So it takes quite a while for effects to show up. It's likely why they made the cost/benefit decision to leave those components out of the system, IF you do the maintenance. It is another maintenance chore either way. But a filter dryer will tend to extend the life of everything in the system. I'd much prefer to have that filter dryer downstream of the tank and put up with the occasional clog at the drain device on the tank.

[javamon]

Originally Posted by memphis02

...I try to purge every time I put the rig up for more than a week or two between trips, now.

Just checked mine out and all the valves were rust free and I could push the pins in with my thumb. It is very new so I'm sure it won't stay that way very long. How do you purge your system? I just kept stepping on the brake pedal and got both gauges pretty close to zero. Is this an acceptable way to purge? Thanks.

[Mnwelsh]

Where is that valve located? Drivers side? Pax side, front, rear.

[SuddenRush]

Originally Posted by Mnwelsh

Where is that valve located? Drivers side? Pax side, front, rear.

Under the driver's side. Near where the exhaust pipe comes out. It's closer to the center of the chassis (left to right), you will see a big air tank and the valve is located at the rear of the tank.

[SuddenRush]

Originally Posted by javamon

Just checked mine out and all the valves were rust free and I could push the pins in with my thumb. It is very new so I'm sure it won't stay that way very long. How do you purge your system? I just kept stepping on the brake pedal and got both gauges pretty close to zero. Is this an acceptable way to purge? Thanks.

I too am curious as to how people purge their systems. Is pumping the brakes, engine off, a suitable solution, or do I need to climb under there and manually purge it each time?

Now that I think about it, I have a 2015, with hydraulic brakes, so I am assuming pumping my brakes won't work. So I am thinking manually purging with the valve is the way to go, unless someone has a more clever way to do it.

Thanks again

[javamon]

Originally Posted by SuddenRush

...Now that I think about it, I have a 2015, with hydraulic brakes, so I am assuming pumping my brakes won't work. So I am thinking manually purging with the valve is the way to go, unless someone has a more clever way to do it.

Thanks again

I think the 2016 models were the first with air brakes. Based on previous posts by robbbyr, the Senecas with hydraulic brakes use air for the emergency brake system. Mine (2017 model) has three of these valves: two on the front tank (one on each end) and one on the back tank.

[Robbbyr]

Originally Posted by javamon

I think the 2016 models were the first with air brakes. Based on previous posts by robbbyr, the Senecas with hydraulic brakes use air for the emergency brake system. Mine (2017 model) has three of these valves: two on the front tank (one on each end) and one on the back tank.

Correct, the pre-air brake Freightliner Senecas use an air operated driveshaft parking brake. It still has a killer spring inside to apply the brake, it uses chassis air to release it. Same appearing dash valve as later air brake Senecas. Will still apply the brake with total loss of air like an air brake Seneca, difference being it locks the driveshaft and not each rear wheel like the air brake-equipped units do. End result is the same however!

As far as the purge valve, my 2014 has just one on the wet tank mounted to the driver side frame rail forward of the rear axle. The valve itself is towards the rear of the tank. It can be manually purged by depressing the center "needle", but you can also do it by cycling the parking brake, provided the valve is working properly and not already clogged with debris. Put unit in neutral (so you have full control of valve), have the wheels chocked or hold foot on service brakes to keep it from possibly rolling. Cycle the parking brake and it should cause the valve to operate. If you have previously located the valve and have a helper cycling the dash valve you may see some moisture escape, but please observe it without being under the unit just in case it would try to roll. Safety first!