adding compressed air outlet?

stlthe · 06-18-2020, 01:58 PM

I have 4 air tanks and dont know which one to tap into for external air outlet for tools, tires, etc.

there is a female quick release connection on the wet tank, which about guarantees water in my air (or needing a large air dryer). I guess it is there to help make draining easier.

I read that there is a logical arrangement of tanks; wet, brakes, brakes, accesories iguess i'll hook into accesory tank if i can identify it.

i just thought of a real question. My air guage has 2 pointers on it. Do you think they are for Brake/accessory pressure, or front brake/rear brake?

Brad_SwiftFur · 06-18-2020, 07:18 PM

You have dual air gauges, as virtually all air braked vehicles will have. Some will have 2 actual separate gauges, others will have the fairly common 2-in-1 gauge, as you have. They are color coded for "P" and "S", Primary and Secondary, respectively.

The reason is because vehicles have 2 separate (sort of) systems. They are connected, because there's only one compressor, but the logic is if one system suddenly fails (depressurizes) the other is there as a failsafe. To this end there are safety protection valves which are designed to allow both systems to pressurize relatively equally, and maintain close pressures, but if one drops suddenly, the valves close and you still have air. These valves are often plumbed between the tanks.

As for your air outlet, I'd skip the wet tank and use whichever conveniently located spot you can find on any of the other tanks - "accessory" preferred, if you have one so marked.

mmoore6856 · 06-18-2020, 08:46 PM

dont forget to use a brake saver valve on the air tank as its required for air brake equipped vehicles on auxiliary systems

Brad_SwiftFur · 06-18-2020, 08:51 PM

Quote:

Originally Posted by mmoore6856

dont forget to use a brake saver valve on the air tank as its required for air brake equipped vehicles on auxiliary systems

I'm not familiar with this term. Are you referring to a "protection" valve which will close between 60-80 PSI (saving air pressure for critical braking in the event of a failure)?

mmoore6856 · 06-18-2020, 09:35 PM

yea thats another name but they close when air drops to 90 the tractor protection valve closes at 65 and is located on your dash. the brakesaver is mounted on the tank

Brad_SwiftFur · 06-18-2020, 10:33 PM

Perhaps "Brakesaver" is a brand name, but I get the idea. The parking brake is supposed to pop out (apply) at around 60 PSI and the protection valve usually doesn't open until around 80 (this is when things like air ride and air seat will get air pressure). Brakes *ALWAYS* get full pressure No Matter What. Parking brakes typically release around 60 PSI +/-. Or, in the case of losing pressure, will begin to drag at around 60 (this may vary a little as things age and wear).

The whole point of this being that if an air line to your air outlet breaks while going down the road, you want that reservoir to be protected from losing all pressure.

Booyah45828 · 06-19-2020, 08:06 AM

If you have an air dryer equipped on the bus, as a lot do, you'll have very little moisture in the wet tank.

If you have an accessory tank, tap into that.

Most have the wet tank tapped so they can inflate the rest of the system if needed.

I'm not sure on the legalities of it, but I wouldn't tap into the primary or secondary tanks. Those quick connect air chucks fail, we have a box of new ones at the shop for when they do. I'd hate to see you stranded or crashed somewhere because of something that stupid.

Native · 06-23-2020, 01:04 AM

Quote:

Originally Posted by stlthe

I have 4 air tanks and dont know which one to tap into for external air outlet for tools, tires, etc.

there is a female quick release connection on the wet tank, which about guarantees water in my air (or needing a large air dryer). I guess it is there to help make draining easier.

I read that there is a logical arrangement of tanks; wet, brakes, brakes, accesories iguess i'll hook into accesory tank if i can identify it.

i just thought of a real question. My air guage has 2 pointers on it. Do you think they are for Brake/accessory pressure, or front brake/rear brake?

The next time you are in the Apopka area, stop by the Freightliner dealer (with your VIN) and ask the parts guys the arrangement of the tanks. You can also talk with their service department and ask where THEY would put in such a tap.

If you have air-ride seats, you can add a "T" in the line that feeds the seat.

mmoore6856 · 06-23-2020, 02:16 AM

Never use thewet tank as the crap in it will plug your tools and the seat supply will not provide a sufficient amount of volume to run some air tools like a impact wrench. Either the primary or secondary will do. Also note sometimes the wet tank is part of one of the large tanks on one end. It is a separt even tho they look like one tank. If so a large line will come out of one end and go back in the back

Winter-Vale · 06-30-2020, 08:01 AM

This was a revelation to us - naifs that we are! I just caught an episode from RollWithIt on YouTube where they tap their air to run the airpower tools and I AM BLOWN AWAY nyuk nyuk nyuk.

demoman · 07-01-2020, 07:27 PM

A way to prevent a leaking air fitting from shutting you down is to put a valve on first then the coupling so you can turn it off or change the coupling if needed without leaking down.
Also the air compressors on most vehicles are not meant for continuous duty. They usually come on to bring the pressure up and then just top off the pressure when brakes are used. The pistons are always moving but the valves are only engaged when needed. I'm not saying you shouldn't use it for airing up tires or running some tools just not as a shop replacement compressor.

Native · 07-01-2020, 08:00 PM

Right .. mainly an emergency tool.

cadillackid · 07-01-2020, 08:30 PM

Quote:

Originally Posted by demoman

A way to prevent a leaking air fitting from shutting you down is to put a valve on first then the coupling so you can turn it off or change the coupling if needed without leaking down.
Also the air compressors on most vehicles are not meant for continuous duty. They usually come on to bring the pressure up and then just top off the pressure when brakes are used. The pistons are always moving but the valves are only engaged when needed. I'm not saying you shouldn't use it for airing up tires or running some tools just not as a shop replacement compressor.

the water cooled compressors are designed for continuous duty, the air cooled ones are not.. Most of the busses built in the mid / late 80s and newer have water cooled compressors (there is coolant in the head). the Bendix Tu-Flo. dual cylinder compressors (500,550,750) series used on our busses are all water cooled heads.. some of the older ones like the Haldex units did not have water in thye heads,, those could overheat and warp the head if run continuously at high pressure.

modern busses use quite a bit of air.. your compressor can easily run continuously as you descend a mountain and are using the Stab and glide method of braking.. where you are pressing the pedal somewhat often and hard then letting off..

**ALWAYS** install your air fitting on the secondary Tank and AFTER a protection valve.. this way if your quick connect leaks it will not shut your braking system down into spring brake apply!!

most modern busses dont have a True "wet" tank.. the first tank is technically the wet tank, however the compressor discharge generally goes directly to the air dryer before going to the first tank.. some residual moisture may condense out in that tank but the air dryer will have done its job by then.

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