air tank purge

[jon48]

My Tiffin RED on a Freightliner chassis has a dryer and auto-purge.  But the tanks have manual pulls.  Questions:

1) why are there 2 pulls on my pax side tank and only 1 on driver side?  What does that 2nd pull do that the other tank doesn't have a second pull?  I crawled underneath to try to figure it out but all I could determine is the location of the valve, not why it is there.  I do know that I need to exercise it ev. 6 mo's and it is an early warning sign for failure of the dryer.

2) The manuals do not refer to a wet tank but I see references online, including this forum.  I presume the pax side on my rig is a wet tank because it has 2 pulls.  But what does that really mean?

3) Freightliner manual refers to tanks as primary and secondary in regards to braking.  But Tiffin refers to Front air ride and Rear air ride.  Comments?

I'm asking all these questions so that I can be informed about how things work.

[bm02tj]

You could have three air tanks that can get moisture 

A primary ,a secondary and possible one for your air ride  that need to be drained

The drier auto purges every time you are up to pressure 

if to often look for the leak 

[jleamont]

Jon48, those tanks should be drained at a minimum once a year. It really depends on how often the coach is used and what conditions it’s operated in i.e. high humidity would need more frequent draining, desert conditions less frequent.

We travel in pretty much the same conditions annually. When we bought our DP I was checking the tanks for water 4 times a year. I have been able to reduce down to once a year as we don’t accumulate water.

I will caution you the more frequently you pull those cords the more likely you are to create air leaks at those valves. I replaced ours with brass petcock’s. The only downside is I have to crawl underneath of hours to drain water out of the air tanks. Our coach doesn’t lower when the air tanks are emptied but not all are this way.
Keep in mind there’s a lot of safety measures you have to take before you crawl underneath of a motorhome with air suspension.

how often are you having the air dryer serviced?

[manholt]

In my 2007 WB Tour DP, I had 2 manual on/off purge lines, ...each morning after driving the day before, I would open each to purge, then close.  I could attach a Air hose on a separate valve, by the generator, for airing up my tires!  With engine on and full pressure, it would purge on Auto.  Freightliner chassis.

The Red is manual and auto, your front is the same as mine was, when you connect air up line, purge first then attach hose.  Your Auto purge is with engine running and up to pressure, about every 3-5 minute you'll get a whoose of air.

The next 3 coach's, including current, it's all Automatic when engine is running.  No manual purge required...Spartan chassis, and one was on Tiffin chassis.

Joe got his in as I was typing.  I have my Air drier service once a year.  

 

[kaypsmith]

Many times, the builder will add a second pull because it is in a more convenient location because of the way the coach was built, ie. you probably only need to purge by either valve. I have chains on all valves that need to be purged that are attached to an outside wall so there is no need to crawl under the coach to purge. Please remember that my coach was an intercity bus that was very low to the ground for air foil purposes, and is the reason for the builder adding chains.

[richard5933]

6 hours ago, jleamont said:

I will caution you the more frequently you pull those cords the more likely you are to create air leaks at those valves.

Those things are designed to be pulled every day at the end of the run. If they leak, then they need to be replaced. We pull them every time we do a pre-trip inspection and during the post-trip inspection on the trucks where I drive. If they are only pulled infrequently, it's quite possible for things to buildup in the tank which will cause the valve to not seal when they are pulled.

Why does the tank have two? Possibly there is an internal baffle in the tank. It has two drains.

[dickandlois]

Richard, I do not need to pull the drains everyday. When There is water when I pull them. The first thing for me to do is change the dryer filters.

And check the governor to make sure it is working properly, so the Compressor runs only for short intervals and is not under load most of the time. This method increases MPG  and will extend the compressor life in most cases. 

Question, Is your coach equipped with an air dryer?

Rich.

 

[wolfe10]

Yes, the BIG IF is whether you have an AIR DRIER.  If so, think of the tank drains as the "report card" for the health/condition of the air dryer.

The air dryer's job is remove both water and oil (the oil lubes the compressor, so a minute amount gets into the air system).

Dryers are normally serviced every three years or so.  I alternate using a FACTORY (i.e. the factory that made the dryer, not a knock off or rebuilt by Bubba) dryer WITH just the filter(s).

The reman dryer includes many wearing components such as valves, heater, etc.

[jon48]

Thanks all for the comments.  I'm sorry I forgot to mention I have a dryer.  It's maintenance interval is 36 mo.

My tanks have pulls in the wheel well so I don't have to crawl under to do the purge.  I crawled underneath to try to determine what was what, couldn't figure it out so posted this query.

I just found a freightliner doc that shows a picture of the tanks set up as a demo floor model (not installed on a chassis).  It shows the wet tank with a "heated automatic moisture ejector".  I guess that is my 3rd pull wire.  I have to double check this. 

I find it odd that I'm supposed to determine if water/oil blows out on manual purge but I really can't operate a pull wire and look underneath at the same time.

I have located the dryer, aft of the rear axle, and just out of curiosity tried to follow the line to see where the air compressor is located but I cannot find it.  I presume it is directly attached to the engine (Cummings) but I'm uncertain of that statement.  The aforementioned doc shows the compressor in the rear attached to the pax side rail but all I find there is the exhaust ATD for pollution control.

[wolfe10]

You should be able to look under the coach at the drain while pulling the tank bleed lanyard to verify that ONLY clean, dry air is coming out.  Water or oil indicates you are past due for dryer replacement/service. If white powder comes out, the dryer has FAILED and that desiccant powder is not into your air system.If it gets past the wet tank, assume all valves and components of your air brake and air suspension system are  compromised.

Yes, the air compressor will very likely be bolted to your engine.  Which Cummins engine do you have-- others may be able to give you specific location.

[jleamont]

Cummins air compressors are located on the passenger side of the engine lowest component, underneath the fuel injection pump. Bolted to the front housing. Typically the power steering/hydraulic pump is bolted to the rear of it. 
Cable pulls are designed to be pulled in a straight line. Most coach builders have them to the left of right. When you side pull them they almost never seat properly and you have to the pull straight to get them to seat again. This happens with brand new valves also. 

If it were me, I’d block the coach so should you lose air it will not injure you, crawl under and Straight pull each one for 1 to 2 seconds just to see if anything comes out. If nothing comes out you know your air dryer is doing its job. That’s typically what I see on our Coach. 

[jon48]

The engine is an ISB 6.7 360HP.  

jleamont:  thanks for great info, especially on the straight pull of valve.

My interest in these cables is that I am required to have a non-commercial class B drivers license and part of the test will be pulling these cables.  It's good to know that the sideways pull may cause a reseating issue.  

[richard5933]

18 hours ago, DickandLois said:

Richard, I do not need to pull the drains everyday. When There is water when I pull them. ..

Rich.

I wasn't commenting on whether or not they should be pulled every day, just they are designed to be. Our trucks have air dryers, and we still pull the cables every day to make sure things are correct. If you don't pull the cable, how do you know if there is water in them? A little water in the brake system or air suspension can ruin your whole day.

14 hours ago, jon48 said:

...My interest in these cables is that I am required to have a non-commercial class B drivers license and part of the test will be pulling these cables.  It's good to know that the sideways pull may cause a reseating issue.  

Likely you won't have to actually pull the cables during the test. They want to make sure you can point to them and that you know what they do. I've tested multiple times as I upgraded my license, and each time they specified that I would not be required to get under the vehicle at any time.