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Topic: Need help with an air leak (Read 1322 times) previous topic - next topic

Re: Need help with an air leak

Reply #25 –
#2 loosen the airline at the compressor with the engine off, no air should be there if the inlet check valve is good on the wet tank.
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: Need help with an air leak

Reply #26 –
Quote from: DayDreamer –

Since both service tanks on our coach will drain when the wet tank is drained via the water drain, I am assuming the check valve on the inlet to the service tanks has failed.


Just to make it easier to swallow when you write the check;

Without these valves working properly you have given up the safety of dual breaking circuits i.e if one circuit has a "blow out" you would automatically lose the other circuit.

There should also be a pilot operated valve to supply bulk air to each brake chamber.  I'm looking forward to learning more about testing those at your expense.  ^.^d
1992 Foretravel Grand Villa
U225 SBID Build No. 4134
1986 Rockwood Driftwood
1968 S.I.A.T.A. Spring
1962 Studebaker Lark
1986 Honda VF700C
1983 Honda VF750C
Charlie, the Dog was broken out of jail 24 Oct 2023
N1RPN
AA1OH (H)e who must be obeyed.

Re: Need help with an air leak

Reply #27 –
Quote from: Old Toolmaker –
There should also be a pilot operated valve to supply bulk air to each brake chamber.
On our (air disk brake, non-ABS) coach there are six valves dedicated to the operation of the brake system:

1.  Treadle valve (brake pedal)
2.  Parking control valve (parking brake knob)
3.  Quick release valve (front brakes)
4.  Spring brake control valve (rear brakes)
5.  Service brake relay valve (rear brakes)
6.  Spring brake relay valve (rear brakes)

I have rebuilt one of them - the parking control valve:

Bendix PP-1 Repair Kit

I have not messed with the others, cuz they are still working properly (I guess...) on our coach.  They are all up in dirty cramped hard-to-get-to places under the coach, so I am putting that project off as long as possible.
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Need help with an air leak

Reply #28 –
Quote from: Old Toolmaker –
Just to make it easier to swallow when you write the check;

Without these valves working properly you have given up the safety of dual breaking circuits i.e if one circuit has a "blow out" you would automatically lose the other circuit.

There should also be a pilot operated valve to supply bulk air to each brake chamber.  I'm looking forward to learning more about testing those at your expense.  ^.^d

Seems like I have been writing a lot of checks lately!  Been salivating at the paint jobs others are getting done, but definitely need to focus on getting it safe first.

By pilot operated valves are you referring to the SPS valves on the drawings?  Took me a while on Google to determine they are Skid Protection Sensitive valves that work with the ABS system.
40ft 1997 U320

Re: Need help with an air leak

Reply #29 –
ABS coaches are different than older models without ABS.  The SPS valves in your diagram must be part of the ABS systems.  It looks like they take the place of the Quick Release valve (front) and the Service Brake Relay valve (rear) on older non-ABS models.

I edited my post above to only pertain to non-ABS systems.
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Need help with an air leak

Reply #30 –
Quote from: DayDreamer –

By pilot operated valves are you referring to the SPS valves on the drawings?  Took me a while on Google to determine they are Skid Protection Sensitive valves that work with the ABS system.

No.  In order to obtain quick response on a pneumatic system, it is customary to place a pilot operated valve near the load, that way when you send a signal it goes through a smaller line that operates the pilot operated valve which moves the bulk air into the device.

You have ABS?  Cool!  I hope they got it right.  When the railroads tried ABS in an attempt to eliminate flatted tires, commuter trains ended up rolling though stations without enough air left to set the brakes.  I'm sure they got it right on your rig.  ;D
1992 Foretravel Grand Villa
U225 SBID Build No. 4134
1986 Rockwood Driftwood
1968 S.I.A.T.A. Spring
1962 Studebaker Lark
1986 Honda VF700C
1983 Honda VF750C
Charlie, the Dog was broken out of jail 24 Oct 2023
N1RPN
AA1OH (H)e who must be obeyed.

Re: Need help with an air leak

Reply #31 –
Quote from: Old Toolmaker –
You have ABS?  Cool!  I hope they got it right. 
Actually, the ABS systems on Foretravel coaches, although they seem to work OK, have caused some problems for our Forum members.

There is a particular "sensor" at each brake unit that is prone to going dead.  When it does, owners have a hard time finding a replacement.  In some cases, it is unobtainable...  I don't know all the details cuz we don't have ABS, but anyone interested in this subject can search the Forum for more info.
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Need help with an air leak

Reply #32 –
Quote from: Chuck & Jeannie –
Actually, the ABS systems on Foretravel coaches, although they seem to work OK, have caused some problems for our Forum members.

There is a particular "sensor" at each brake unit that is prone to going dead.  When it does, owners have a hard time finding a replacement.  In some cases, it is unobtainable...  I don't know all the details cuz we don't have ABS, but anyone interested in this subject can search the Forum for more info.

It's the rear ABS sensor on late 90's coaches.  OEM size and style not available.  The new part number that replaces it does not fit those coaches.

1998 U 270 rear ABS sensor source and part number
Learn every day, but especially from the experiences of others. It's cheaper!  - John C. Bogle

2000 U320 36' non-slide / WildEBeest Rescue
2003 U320

Re: Need help with an air leak

Reply #33 –
Replaced the check valves on both service tanks today with new Haldex KN23000 check valves.  They are working great.  Now when I drain the wet tank, both service tanks hold air!  Hope I never have to rely on them, but feeling a little safer. Looks like you can also get just the internals as part RN10Y, but it is not that much cheaper.
 
Also replaced a leaking regulator on the step with one from Home Depot.  Still have some minor air leaks to find/fix, but only lost 4 psi over an hour.
40ft 1997 U320