[Archived]

I’m so jealous of your ability to draw inbetween/on the lines. My attempt of doing similar failed.. luckily it looks like we have close enough schamatics so imma just print yours 🙂

My understanding its this valve that connects the primary to secondary to accessory tank. IDK where that physically is located or if you replaced that but if I were you I’d remove and cap each side to see which one drains. Not sure where the check valves are

[justin]

Hello Captain – THANK YOU for your review and I think you very well may have found it!

I have looked at that exact spot more than a few times – both on paper and at the secondary tank – yet did not comprehend it – due to the fact when performing tank drains in sequence, it did not appear to be leaking – because it is a very slow leak.

In the attached photo, I have circled the check valve in blue.

“Studying” it again since you pointed it out, makes perfect sense.

That check valve must have a VERY SLOW leak, which is NOT noticeable when draining all tanks in the proper sequence to test the check valves.

IF it is not bad, seems only the primary and aux tanks would go down simultaneously (because of aux leaks would simultaneously drain the primary)

I have spent a lot of time and dollars over the past near five years getting the aux system pretty darn leak free, yet still new aux leaks, of course, pop up.

THANK YOU AGAIN and check the Articles Section of this website soon as I just submitted the PDF of that drawing which you can get enlarged at a print shop in far better quality than the photos I took of the drawing.

I just submitted the PDF and it is awaiting admin approval.

THANK YOU AGAIN 🙂

P. S. – if you reply to this or any other post, you will see at the top of the page IN BLUE PRINT, “Do you want to update your profile?” You might consider doing so and adding your email address which would then allow someone to email you by clicking on your name (captain). You could also add info on your coach if you would like. Email me if admin does not approve the drawing to be added to the Articles Section and I will email it back to you. Thanks again, Jeff

[DON]

Check valves are important and I have 3 R12 valves and 1 R14 valves I replaced all 5 years ago If you look at schmatics 3 R12 valves only get air when the control port gets air when you apply brakes, When I seperated air lines between wet tank and pedelvalve it held 4 cheap gauges and some fittings told me alot. You can see 1st pic that one valve seperates the aux from brakes If it’s anything like mine but newer Primary and secondary Is only for brakes and e-brakes and belt tension on engine, Aux system only Suspension and add on’s from converter If you shut off 1 st valve your leaks will be in brake system, Other valves I added are air horn-air seat-air door lock-foot well slide If I get a leak in any of those thing easy to turn off Art & Teri 1997 Prevost Royale Templeton Calif, The new Wine Country

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[TRUE]

Awesome I’ll grab the high res photos. Luckily I have some wide format printers and photo printers so will print it all blown up.

Also will update my info now, didn’t realize that

[Mike, 92 Country Coach]

Try dumping the tanks at a high rate. My tanks will all go down at the same rate over a few days, BUT if I dump the air quickly the check/oneway valves work/hold.

Haven’t figured out why yet.

Chuck

[Mike, 92 Country Coach]

A leaking check or protection valve will slow the leakage from all tanks, but if the leak rate at the source, such as at a relay valve is slow it will allow all tanks to drain.

[Art]

DARN…. Changed my secondary air tank check valve, yet all 3 tanks continue to drain at the exact same rate…. have been chasing this for at least 2 years…. have replaced so many valves and fittings to no avail 🙁

[Jeff]

Have the same issue with all 3 tanks slowly leaking down. Spoke with Robert Hitt ar the Prevost Expo. He said there are only 3 places the tanks combine/could leak.

* Emergency brake
* Valve under brake pedal (I believe that’s the treadle valve).
* R 12 valves

Robert said a trick they use is to air up the system, stretch a balloon over the exhaust ports on the R 12 valves and see if one inflates indicating a leak.

Chuck

[Joshua]

Thank you Chuck. Will try the balloon trick. Have checked with better bubble as well as an ultrasonic leak detector with no luck.

Replaced one of two R-12’s as one was replaced about 5 years ago.

Replaced the SR-7 valve, which I assume is what he is referring to as the “emergency brake”.

Have also tested the treadle valve for leaks as described above with none showing.

Soon to leave for AZ, and after my return, I am going to check the trailer air brake valve optioned on my bus (glad hands)

What will make it difficult is that in order to access this valve, and the 3-port Norgren that raises the tag, as well as the “Inversion” valve, I must either remove two Outback inverters or the primary air tank. Not looking forward to this project, yet will re-locate all 3 for easy future access.

[Chuck & Katrina]

If your check valves on your Primary and secondary and leaking just a little and air dryer check valve is leaking back to engine compressor or governor from wet tank they will all leak down, If you drain wet tank remove stainless line to governor from wet tank and put a gauge on it and use house air fill system to 120psi and watch gauge, I replaced my governor this last time

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2000 Featherlite H3-45

2024 Jeep Grand Cherokee

Leesburg, FL

[Bill]

Jeff

You are correct, e brake is parking brake.
R-12s on my Featherlite are behind the D/S & P/S rear fender, problem is my 8 house batteries are behind the P/S fender and have to be removed along with a aluminum horizontal plate behind the batteries to access the P/S R-12s. Been avoiding the repair due to access, but leaks are getting to the point I will need to deal with it sooner than later.

Chuck

[Alex]

An important air system check is to air up the bus and shut it down. With all 4 tanks pressurized, starting with the wet tank you should be able to drain each tank in sequence (wet, primary, secondary, accessory) and each succeeding tank should retain its pressure.

You are doing two very important things. Obviously you are draining any accumulated moisture. If you have maintained the dryer or water separator on the conversion side of the accessory tank, each tank should be bone dry.

The second thing is you are verifying the various check and protection valves are functioning as intended so a catastrophic loss of air pressure in one part of the system does not render the rest of the systems inoperative.

Based on the discussion above I am pretty sure the simultaneous leaking is a signal to me that not only is something leaking to atmosphere, but that within the system check valves or protection valves are also leaking. I doubt if the problem has a single cause.

[Jon]

Jon:

Have drained tanks in sequence per your description, each remaining un drained tank held it’s pressure indicating check valves are working. My current conversation with Robert Hitt from Prevost indicated all 3 tanks can (slowly) leak down even with the check valve’s working properly. Robert said there are 3 sources where that can happen.

*Parking brake

*I believe it’s called a treadle valve. Valve under the brake foot pedal

* R-12s

Chuck

P.S. Robert noted the R-12s are usually the culprit.

[Andrew]

I agree with the R-12 valves, and yield to Robert’s expertise, but think about this for a moment.

Your 3 bus systems are literally separate systems. You can run a tank leak down test but if the leak in the system between them is relatively small such as a similar size to an R12 leak all three will go down simultaneously.

The reason for the valving between them is to insure if on has a catastrophic failure the others will still retain pressure.

I may be misinterpreting how the systems are set up and protected, but I cannot envision fully functioning valving allowing the systems on a non-leaking relay valve to lose pressure. Maybe the second problem is not a check valve for example, but 2 relay valves. I just do not think only one defect is the cause.

[Jeff]

Jeff,

I believe some of your coloring on your treadle valve is incorrect. Shouldn’t there be two more green lines? You have them as red.