Ok you *Air system* gurus, I need either help, or a confirmation please.

[FIRE UP]

Hey gang,
Well, some of you may have followed my thread on "Houston, we have a problem" which, was all about a serious leak in one of my air bags (Freightliner calls them "Air Springs"). My drivers side had a serious leak in it. So, I changed it. Then, decided it was just best, if I changed ALL the air bags. So, I did. The rears also had some slight bubbling when I sprayed them. So, while my hopes were up that I'd actually eliminated ALL my air leaks with the changing of all four air springs, NO SUCH LUCK!

I took the coach out of it's cave, washed it and drove it around with the new air springs and then backed it in this evening. Guess what, I could still actually hear another leak. CRAP! So, I decided to slide my fat body under the big girl, in the front area 'cause that's where I heard the leak. Based on my angle of spraying of everything I could see, no luck in finding it. But, I could hear it. Hmmmm.

Just for grins, I went and got my doctors stethascope that I converted to hear things like exhaust leaks, door seal leaks on cars/trucks etc. I slid back under the coach and, started holding the tip of that scope at various parts/joints/fittings etc. Then, all of a sudden, ZAP, there it was/is. It is what you see in the picture. It's basically a 2-way Tee with a little red rubber type cap sticking out of the center outlet.

I could put my fingers on it and push that little red rubber cap/component in and out, like it was some sort of valve. That would actually make the leak slow waaaaaay down, to the point I could not hear it any more. But, when I withdrew my fingers, it continued to leak. I could actually spin that little red rubber piece too.

Soooooo, I'm not the most versed in air system components other than I know what brake cans are, a treadle valve and a couple other items. But this one is new to me. So, I got onto DTNA connect and looked up my coaches air system. From my investigation, the closest I can come to the I.D. of this thing is, a *Pressure Protection Valve*!

So, based on the picture below, can one or more of you air system execs help this old geezer out and either confirm my findings or, correct me if you know EXACTLY what this component is. I'd surely appreciate it. Thank you way in advance.
Scott

[JaminSamin]

This was covered in a recent thread, at least it looks like the same part...pressure protection valve (PPV).
https://www.irv2.com/forums/f26/what...rt-521526.html

[Unplanned Tourist]

Yep, it cuts air supply to accessories like seats, horns, etc. to save air pressure for important things like brakes.

[Skip426]

Scott ; if you can follow the black tube to the air suspension distribution manifold, then confirmed it's the PPV .

My diagrams shows a second PPV ,"Td" off the front brake air line for ; customer manifold/air horn and exhaust brake.

Although from your picture , you have a second one further back on the tank.

[FIRE UP]

Skip and others,
Well, since basically confirming that my leaking component was a pressure protection valve, and that I had the part number from DTNA connect, I did my usual and cruised the phone lines with local auto parts stores including a Napa. Our local Napa was for the most part, useless. I did find one at a Carquest. I'd seen them on line for around $21-$25 for the most part. But, the one at Carquest was a whopping $60.00!!!!!!!!!!!!

So, I thought what the heck, let's try the closest Freightliner, about an hour away in Kingman. "Yep, we got ONE, and it's $17.60". Sooooo, jumped on the motorcycle and headed up to Kingman. I got back a couple hours later and, drove the coach up on some ramps in the RV cave. I dumped the air bags but, still had around 100 psi in the front gauge, by the generator. So, I tried pulling on the cables that you pull to drain moisture from the tanks. Well, I'd be there for the entire year of 2021 if I kept that up.

So, I decided to yank the black air line from that PPV and whatever was in that tank would immediately vent. Well, I did just that and, when that hose popped out, no air came out. Hmmmm. Oh well. I'll now just unscrew the valve. Psssssssssshhhhhh!!!!

That tank instantly vented when that valve was removed. No biggie. I removed the one plug and push-to-connect fittings from it and installed them on the new one. I installed that new one and, cleaned and inserted the black air hose into the push-to-connect fitting. The moment of truth. I jumped in and fired the CAT C-7 up.

I waited to 'till the dryer spitted and then shut the coach off. The bags were filled and the air system was topped off. I then grabbed my trusty spray bottle, my high speed creeper and, I zoomed under the coach to check for leaks. The only leak I could find was the the push-to-connect fitting. It appears it's leaking behind the collar that you push to release the hose. But, the leak is so infinitely small, as in a single set of micro bubbles, about 3-5 every 3-5 minutes. In other words, at this point in time, that's hardly worth messing with.

The compressor stopped at 125 psi, according to the air gauge up front, above the generator. That was right around 4:00. I checked it again at about 7:00 and, it's at 123 psi. It's now 10:00 P.M. and, it's still between 122 and 123, the gauge is not that incremented. Sooooo, at this point in time, I'm a happy camper. My air system in this coach, has always had some leakage. I've tried a few times years ago to find any but, never succeeded. It will be interesting to see what the pressure is in the morning.
Scott

[Unplanned Tourist]

Great you are airtight!

[twinboat]

Next time pump the brakes to drain the tanks, they don't have pressure protection valves.

[FIRE UP]

Originally Posted by twinboat

Next time pump the brakes to drain the tanks, they don't have pressure protection valves.

Hey twinboat,
Not sure I follow you. Are you saying that pumping the brakes will drain both tanks? While I've been around air brake systems for almost my entire life, (fire career for well over 35 years), I guess I've just not really got into them to study all the parts and components. I would like to know a lot more, just for my own satisfaction. By the way, 14 hours later, after installing that PPV and, topping off the system, I'm still at 120 psi this morning at 09:00, YAHOOOOOOOOOOOOOOOO!
Scott

[twinboat]

Yes, air brake systems are split systems, primary for rear and secondary for front brakes.

Along with that, there are double check valve tee's, that will direct air to all brakes, in the event of one tanks total air loss.

There is also an inversion system that will allow the spring brakes to apply by, regulating the air release of the spring chambers, when the air is critical low, but not low enough to cause an emergency stop.

That gives you a controlled stop or two, to get out of traffic while the low air alarm is sounding.

Google " FMVSS No. 121 air brake systems "

[FIRE UP]

Originally Posted by twinboat

Yes, air brake systems are split systems, primary for rear and secondary for front brakes.

Along with that, there are double check valve tee's, that will direct air to all brakes, in the event of one tanks total air loss.

There is also an inversion system that will allow the spring brakes to apply by, regulating the air release of the spring chambers, when the air is critical low, but not low enough to cause an emergency stop.

That gives you a controlled stop or two, to get out of traffic while the low air alarm is sounding.

Google " FMVSS No. 121 air brake systems "

Thank you very much for that. I think I remember some of that info from some of my FD mechanic classes but, that was a loooooooong time ago. So, I will look up your link to refresh.
Scott

[basketball]

Had a leak in mine also. Took part out and headed to a heavy truck repair shop. Make sure they do air repair. Had one sitting on the shelf( quite common in air systems). Make sure you check the size of the threads into the air tank. They do come in different sizes.
Cost $15.00

[96 Wideglide]

Originally Posted by Skip426

Scott ; if you can follow the black tube to the air suspension distribution manifold, then confirmed it's the PPV .

My diagrams shows a second PPV ,"Td" off the front brake air line for ; customer manifold/air horn and exhaust brake.

Although from your picture , you have a second one further back on the tank.

Judging by the weld on that tank, it's a split tank. Half wet tank, half front primary dry tank.

[FIRE UP]

Originally Posted by 96 Wideglide

Judging by the weld on that tank, it's a split tank. Half wet tank, half front primary dry tank.

You're more than likely correct. I have three cables for yanking on to check for moisture but, only two actual tanks.
Scott