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Old 07-05-2020, 09:27 PM   #1
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Air Bleed Discharge Upgrade

The air system bleed valve in the engine service bay spewed oil and water into the bay each time the tank was bled. Also there were two independent bleed valves when only one was needed. This project increased the bleed line size and combined both discharge ports into a single bleed system draining the tanks below the engine service bay where the discharge can be caught in a container.

https://safaritoonces.org/safari-too...de-engine-bay/
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Old 07-06-2020, 04:03 AM   #2
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If you have a properly working air dryer, there shouldn't be much, if any, oil and water getting into the tanks.

Air dryers are designed to collect and then expel that, before it gets in the tanks.
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Old 07-06-2020, 07:02 AM   #3
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I will admit that I know very little about the air systems. I have one pull lanyard on each side in wheel well. Those lanyards open up the relief value for each air tank. I myself can not see the need to combine the two. If I understand, you would have two open relief values feeding air down to a master value. to me that would be an accident waiting to happen.

Good luck however.
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Old 07-06-2020, 07:50 AM   #4
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Now that I looked over your post again, I see that by combining the 2 seperate drain valves into one, you have altered the air system.

That tank with the 2 drains is actually a 2 chamber tank. The weld seem, going around the tank, is the seperate of each side.

The shorter section is called the wet tank. It is the tank that controls the compressor operation. It also supplies the primary and secondary tanks. That is done thru a double check valves as a safety feature, in the event of a line rupture.

The double check valves are installed as a safety device. Your fix bypasses some of that system.
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Old 07-06-2020, 08:15 AM   #5
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I watched the entire video and would like to add a few things...

A air brake system has a minimum 3 tanks.
1. Wet tank- this tank is the 1st one to receive air from compressor, and air dryer.
2. Primary tank- supplies air to rear brake system.
3. Secondary tank- supplies air to front braking system.

There's a one-way check valves between each tank that will not allow air to flow back into a tank that suddenly looses air.

By plumbing the drains together as shown in the video, the safety system of the one-way check valves are bypassed, and if sudden loss of air could cause a loss of brakes and parking/spring brake to apply at road speed.

Hopefully the OP fully understands a air brake system and installed a check valve in between the "combined drain line" added
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Old 07-06-2020, 08:51 AM   #6
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Now that I looked over your post again, I see that by combining the 2 seperate drain valves into one, you have altered the air system.

That tank with the 2 drains is actually a 2 chamber tank. The weld seem, going around the tank, is the seperate of each side.

The shorter section is called the wet tank. It is the tank that controls the compressor operation. It also supplies the primary and secondary tanks. That is done thru a double check valves as a safety feature, in the event of a line rupture.

The double check valves are installed as a safety device. Your fix bypasses some of that system.
+1 - it' ain't like it used to be.
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Old 07-06-2020, 08:53 AM   #7
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I will admit that I know very little about the air systems. I have one pull lanyard on each side in wheel well. Those lanyards open up the relief value for each air tank. I myself can not see the need to combine the two. If I understand, you would have two open relief values feeding air down to a master value. to me that would be an accident waiting to happen.

Good luck however.
On my Freightliner I've got three lanyards - one for each tank. Your rig may be entirely different - however you might want to look for another lanyard - sometimes they are lost/never pulled through the frame or buried in undercoat.

My apologies if I'm sending you on a wild goose chase.
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Old 07-06-2020, 09:05 AM   #8
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....why not just replace the manual drains with a Bendix DV-2 automatic drain valve.... Screws into bottom of each tank, maintenance free. Click image for larger version

Name:	170281923__69544.1505948956.jpg
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Size:	27.5 KB
ID:	292161
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Old 07-07-2020, 08:31 AM   #9
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....why not just replace the manual drains with a Bendix DV-2 automatic drain valve.... Screws into bottom of each tank, maintenance free. Attachment 292161
Many semi-trucks use the automatic drains and they work.

But they are expensive (compared to the manual drain vales), and they do fail. Those automatic drains will get dirt/grit in the valve seat and leak air. The manual drains can also suffer from this problem too but if one does start to leak its easy to jiggle the lanyard/valve to clear out the debris.
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Old 07-07-2020, 05:19 PM   #10
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It's funny I see such a huge difference in prices 20 to 200 and 35-250 for heated. For basically same body.
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Old 07-08-2020, 01:49 AM   #11
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+1 - it' ain't like it used to be.
I did a post on the air system corrections that explain the connections. On a full air brake system you would be correct, however this system uses the air for the airbags, Pac brake, emergency brake, air horns and step slide.

The compressor feed goes in at the wet end from the compressor and all air lines are fed from the top of the dry end of the tank. There is no redundancy. The two drains are unlikely to fail and serve only to drain water, again there is no reason to drain them separately. Even if there was a failure of both drain ports it would not affect the systems. The air compressor, I checked and according to CAT produces 13.5 CFM. That is a lot of air.

I will do a test with the engine running and the bleed values open to see what happens and post the result. again I would agree with you if this were a full air brake system but it has hydraulic brakes. This was detailed in the main' presentation on the air system. If you look at the index under mechanical it is there. I continued on based on the previous presentations information, but I will explicitly point this out in this last project. Thank you. http://safaritoonces.org
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Old 07-08-2020, 01:54 AM   #12
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That is true for a system with air brakes. This was a change for a coach with hydraulic brakes. The main presentation noted such, but I will update the presentation to clarify thanks for pointing this out.
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Old 07-08-2020, 10:54 AM   #13
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Originally Posted by blewis9991 View Post
I did a post on the air system corrections that explain the connections. On a full air brake system you would be correct, however this system uses the air for the airbags, Pac brake, emergency brake, air horns and step slide.

The compressor feed goes in at the wet end from the compressor and all air lines are fed from the top of the dry end of the tank. There is no redundancy. The two drains are unlikely to fail and serve only to drain water, again there is no reason to drain them separately. Even if there was a failure of both drain ports it would not affect the systems. The air compressor, I checked and according to CAT produces 13.5 CFM. That is a lot of air.

I will do a test with the engine running and the bleed values open to see what happens and post the result. again I would agree with you if this were a full air brake system but it has hydraulic brakes. This was detailed in the main' presentation on the air system. If you look at the index under mechanical it is there. I continued on based on the previous presentations information, but I will explicitly point this out in this last project. Thank you. http://safaritoonces.org
....Unfortunately, I don't agree and think this could result in total brake failure in the event of a air leak anywhere in the system. The system will not stop the vehicle with no air psi....the foot valve is air operated, You should have 4 lines to the foot valve, supply and deliverly for both the primary and secondary system.

No air psi = no master clyinder movement=no brakes. EVEN with your 13.5 (standard rating) air compressor it's would not build up enough to stop the unit....You may test this by opening up the drains and seeing how long it takes to build up air pressure, or if your that sure just drive off with the drains open!
You may have a driveline mounted parking bake, but I would't count on it to stop the vehicle.

The air tanks were required to have a check valve between them that keeps air in the tank thats not leaking. It's not "drain failure" failure that could cause issue, By tying the drains together, you've given the air a path to go on into the tank with less (leak)pressure.

OP, It's your coach, do as you please, and while not meaning to offend, just want to make sure that someone else that thinks this is a good thing, that they could possiably create a un-safe sutiation by altering the as designed air brake system side of the vehicle.
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Old 07-08-2020, 11:25 PM   #14
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If you have a properly working air dryer, there shouldn't be much, if any, oil and water getting into the tanks.

Air dryers are designed to collect and then expel that, before it gets in the tanks.
I put an air dryer on some of the equipment after the tank discharge... Pac brake, dash gauge, horns, stepwell cover, but there is no air dyer ahead of the tank fed from the compressor feed to the tank. I know same people have put dryers into the system after the compressor but these coaches were not designed that way. There's a lot of water that collects. The brakes are hydraulic and not air.
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