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Air leaking from front when brakes applied - Printable Version +- Wanderlodge Gurus - The Member Funded Wanderlodge Forum (http://www.wanderlodgegurus.com) +-- Forum: Yahoo Groups Archive (/forumdisplay.php?fid=61) +--- Forum: WanderlodgeForum (/forumdisplay.php?fid=63) +--- Thread: Air leaking from front when brakes applied (/showthread.php?tid=8552) Pages: 1 2 |
Air leaking from front when brakes applied - gregory O - 11-02-2009 01:21 could be "double check valve" ? anyway I dont believe it is designed to continualy release air while service brake is applied. I think it directs the service psi to the spring psi. 90 psi + 90 psi = 90 psi but mechanical force of 1,000 psi and another mechanical source of 1,000 psi = 2,000 psi which is where the shoes crack. My higheel is done and on the bus. folds up to 14 foot high then lifts automaticaly to 19.5 foot tall I will post pict later, parade is Sunday Greg 94ptca --- In WanderlodgeForum@yahoogroups.com, Curt Sprenger > > Greg, > Good information for sure, thanks! Do you know the BlueBird name for that > compounding valve? > > Curt Sprenger > 1987 PT38 8V92 "MacAttack Racing" > Anaheim Hills, CA > > > > On Sun, Nov 1, 2009 at 7:21 PM, gregory O > > > > > > > it is the anti compouning valve blowing air ?? when the spring brake is > > left pushing (park brake on) and someone pushes on the service brakes, the > > valve proportions the pressure working the cams on the axle that hold the > > spring brakes so there is not too much pressure on the shoes. if the valve > > is crapped out you get broken shoes with no sign of heat that made the > > cracks . > > > > > > to keep from giving a lecture then getting a lecture from the mods, check > > out page 27 of Bendix handbook<http://www.wsafc.org/WSFMA/Shared%20Documents1/Bendix%20Air%20Brake%20H\ andbook.pdf> > > > > > > > > > > http://www.wsafc.org/WSFMA/Shared%20Documents1/Bendix%20Air%20Brake%20Handbook.p\ df > > > > here is a good video of the principles of AB<http://www.youtube.com/watch?v=qJa5-_ExsBE> > > without much of the new safety crap confusing the process it is from 1967 > > > > http://www.youtube.com/watch?v=qJa5-_ExsBE > > > > Greg > > 94ptca > > > > > > > > --- In WanderlodgeForum@yahoogroups.com, Curt Sprenger > > wrote: > > > > > > Paul, > > > > > > What you found and determined does not seem right. Post pictures if you > > can. > > > I looked under our coach this afternoon. I see a 1/8" plastic air line to > > > the cylinder that rotates down the driving light. Above that area on the > > > bottom of the frame rail there are some copper and plastic air lines. > > None > > > are open as you describe. > > > > > > Curt Sprenger > > > 1987 PT38 8V92 "MacAttack Racing" > > > Anaheim Hills, CA > > > > > > > > > > > > On Sat, Oct 31, 2009 at 2:35 PM, P & D audvid1@ wrote: > > > > > > > > > > > > > > > Thanks you all for the assistance. Got some help today and we climbed > > > > under coach and found a Ãâü air line on the driver side front right > > behind the > > > > > > fog lights that when you step on the brakes air comes out of that line > > and > > > > as soon as let off it stops. After looking at drawings and trying to > > figure > > > > out where the other end should be connected, by accident we discovered > > that > > > > if you plug the hose, the coach emergency brake released. (Good thing > > we > > > > are on a level lot) and if you un plug it, the emergency brakes stay > > > > locked. Then we tried it with the emergency brake released and no air > > came > > > > out, so I think it is releasing the air bypassing the emergency brake > > so as > > > > to not release the emergency brake. > > > > > > > > > > > > > > > > Hope all that made sense, but it appears that is normal operation, > > although > > > > I never recall hearing that noise before when I stepped on the brake. > > > > > > > > > > > > > > > > Thanks again for all the help > > > > > > > > > > > > > > > > Paul & Debbie Potter > > > > > > > > Hesperia CA > > > > > > > > 1987 PT 38 > > > > > > > > Hotel California II > > > > > > > > > > > > > > > > *From:* WanderlodgeForum@yahoogroups.com [mailto: > > > > WanderlodgeForum@yahoogroups.com] *On Behalf Of *Wayne Kotila > > > > *Sent:* Monday, October 26, 2009 1:56 PM > > > > *To:* WanderlodgeForum@yahoogroups.com > > > > *Subject:* Re: [WanderlodgeForum] Air leaking from front when brakes > > > > applied > > > > > > > > > > > > > > > > > > > > > > > > Did you check the rubber hoses to the front brakes? When you step on > > the > > > > brake pedal air pressure applies your front brakes so you will have air > > > > pressure in the supply hoses to until you take your foot off the brake > > > > pedal. Sometimes from age those hoses will start leaking where the end > > is > > > > crimped on the hose and if you need to replace them, a farm supply > > store > > > > will carry high pressure hydraulic hose in different diameters and > > lengths > > > > and have different end adapters to convert the end connector to what > > you > > > > need. You should be able to get a new hose and adapters if needed for > > under > > > > $20.00. > > > > > > > > Wayne > > > > > > > > 1996 WB42 > > > > > > > > > > > > ------------------------------ > > > > > > > > *From:* ppotter14950 audvid1@ > > > > *To:* WanderlodgeForum@yahoogroups.com > > > > > > *Sent:* Sun, October 25, 2009 9:38:25 PM > > > > *Subject:* [WanderlodgeForum] Air leaking from front when brakes > > applied > > > > > > > > > > > > > > > > Hi there > > > > > > > > Today while finishing up Air Force One supplemental braking install for > > > > towed vehicle, had engine off and when applied brakes to test Air Force > > One > > > > and while pedal was depressed there was a constant air leak up front > > around > > > > the left front area, but could not find it. Any suggestions on where it > > > > might be, will work on taking front driver side panel open and looking > > in > > > > there, but it is so tight in there and i dont know what i am looking > > for so > > > > any suggestions would be appreciated. > > > > > > > > Thanks > > > > > > > > Paul & Debbie Potter > > > > 87PT40 - Hotel California II > > > > Hesperia CA > > > > > > > > > > > > __________________________________________________ > > > > Do You Yahoo!? > > > > Tired of spam? Yahoo! Mail has the best spam protection around > > > > http://mail.yahoo.com > > > > > > > > > > > > > > > > > > > > Air leaking from front when brakes applied - P & D - 11-02-2009 15:13 Wow, that is a bunch of good material, but I may still be To add more to this mystery, it was just in the shop and they Thanks for all the info too Paul 87pt38 Hesperia CA From: it is the anti compouning valve blowing air ?? when the spring brake is left pushing (park brake on) and someone pushes on the service brakes, the valve proportions the pressure working the cams on the axle that hold the spring brakes so there is not too much pressure on the shoes. if the valve is crapped out you get broken shoes with no sign of heat that made the cracks . to keep from giving a lecture then getting a lecture from the mods, check out page 27 of Bendix handbook http://www.wsafc.org/WSFMA/Shared%20Documents1/Bendix%20Air%20Brake%20Handbook.pdf here is a good video of the principles of AB without much of the new safety crap confusing the process it is from 1967 http://www.youtube.com/watch?v=qJa5-_ExsBE Greg 94ptca --- In WanderlodgeForum@yahoogroups.com, Curt Sprenger wrote: > > Paul, > > What you found and determined does not seem right. Post pictures if you can. > I looked under our coach this afternoon. I see a 1/8" plastic air line to > the cylinder that rotates down the driving light. Above that area on the > bottom of the frame rail there are some copper and plastic air lines. None > are open as you describe. > > Curt Sprenger > 1987 PT38 8V92 "MacAttack Racing" > Anaheim Hills, CA > > > > On Sat, Oct 31, 2009 at 2:35 PM, P & D audvid1@... wrote: > > > > > > > Thanks you all for the assistance. Got some help today and we climbed > > under coach and found a ü air line on the driver side front right behind the > > fog lights that when you step on the brakes air comes out of that line and > > as soon as let off it stops. After looking at drawings and trying to figure > > out where the other end should be connected, by accident we discovered that > > if you plug the hose, the coach emergency brake released. (Good thing we > > are on a level lot) and if you un plug it, the emergency brakes stay > > locked. Then we tried it with the emergency brake released and no air came > > out, so I think it is releasing the air bypassing the emergency brake so as > > to not release the emergency brake. > > > > > > > > Hope all that made sense, but it appears that is normal operation, although > > I never recall hearing that noise before when I stepped on the brake. > > > > > > > > Thanks again for all the help > > > > > > > > Paul & Debbie Potter > > > > Hesperia CA > > > > 1987 PT 38 > > > > Hotel California II > > > > > > > > *From:* WanderlodgeForum@yahoogroups.com [mailto: > > WanderlodgeForum@yahoogroups.com] *On Behalf Of *Wayne Kotila > > *Sent:* Monday, October 26, 2009 1:56 PM > > *To:* WanderlodgeForum@yahoogroups.com > > *Subject:* Re: [WanderlodgeForum] Air leaking from front when brakes > > applied > > > > > > > > > > > > Did you check the rubber hoses to the front brakes? When you step on the > > brake pedal air pressure applies your front brakes so you will have air > > pressure in the supply hoses to until you take your foot off the brake > > pedal. Sometimes from age those hoses will start leaking where the end is > > crimped on the hose and if you need to replace them, a farm supply store > > will carry high pressure hydraulic hose in different diameters and lengths > > and have different end adapters to convert the end connector to what you > > need. You should be able to get a new hose and adapters if needed for under > > $20.00. > > > > Wayne > > > > 1996 WB42 > > > > > > ------------------------------ > > > > *From:* ppotter14950 audvid1@... > > *To:* WanderlodgeForum@yahoogroups.com > > *Sent:* Sun, October 25, 2009 9:38:25 PM > > *Subject:* [WanderlodgeForum] Air leaking from front when brakes applied > > > > > > > > Hi there > > > > Today while finishing up Air Force One supplemental braking install for > > towed vehicle, had engine off and when applied brakes to test Air Force One > > and while pedal was depressed there was a constant air leak up front around > > the left front area, but could not find it. Any suggestions on where it > > might be, will work on taking front driver side panel open and looking in > > there, but it is so tight in there and i dont know what i am looking for so > > any suggestions would be appreciated. > > > > Thanks > > > > Paul & Debbie Potter > > 87PT40 - Hotel California II > > Hesperia CA > > > > > > __________________________________________________ > > Do You Yahoo!? > > Tired of spam? Yahoo! Mail has the best spam protection around > > http://mail.yahoo.com > > > > > > > Air leaking from front when brakes applied - gregory O - 11-02-2009 16:00 slack adjusters on the drive axle got damaged? I believe tcompounding cauld damegd the slack adjusters. the drive is the axle with the park brakes (drive axle has four tires)( Tag has one each side). Greg 94ptca --- In WanderlodgeForum@yahoogroups.com, "P & D" > > Wow, that is a bunch of good material, but I may still be confused about the > anti-compound valve, is it working correctly or not working correctly. > > > > To add more to this mystery, it was just in the shop and they had to replace > 2 stripped auto slack adjusters to the brakes, could this have been because > too much pressure was applied with both the parking and regular brakes > applied at the same time? Also when I plugged the hose, the spring brake > released, is that what you want it to do if you have applied the brakes. > > > > Thanks for all the info too > > > > Paul > > 87pt38 > > Hesperia CA > > > > From: WanderlodgeForum@yahoogroups.com > [mailto:WanderlodgeForum@yahoogroups.com] On Behalf Of gregory O > Sent: Sunday, November 01, 2009 7:21 PM > To: WanderlodgeForum@yahoogroups.com > Subject: [WanderlodgeForum] Re: Air leaking from front when brakes applied > > > > > > it is the anti compouning valve blowing air ?? when the spring brake is > left pushing (park brake on) and someone pushes on the service brakes, the > valve proportions the pressure working the cams on the axle that hold the > spring brakes so there is not too much pressure on the shoes. if the valve > is crapped out you get broken shoes with no sign of heat that made the > cracks . > > > to keep from giving a lecture then getting a lecture from the mods, check > <http://www.wsafc.org/WSFMA/Shared%20Documents1/Bendix%20Air%20Brake%20Handb > ook.pdf> out page 27 of Bendix handbook > > > http://www.wsafc.org/WSFMA/Shared%20Documents1/Bendix%20Air%20Brake%20Handbo > ok.pdf > > here is a good video of <http://www.youtube.com/watch?v=qJa5-_ExsBE> the > principles of AB without much of the new safety crap confusing the process > it is from 1967 > > http://www.youtube.com/watch?v=qJa5-_ExsBE > > Greg > 94ptca > > > --- In WanderlodgeForum@yahoogroups.com, Curt Sprenger > wrote: > > > > Paul, > > > > What you found and determined does not seem right. Post pictures if you > can. > > I looked under our coach this afternoon. I see a 1/8" plastic air line to > > the cylinder that rotates down the driving light. Above that area on the > > bottom of the frame rail there are some copper and plastic air lines. None > > are open as you describe. > > > > Curt Sprenger > > 1987 PT38 8V92 "MacAttack Racing" > > Anaheim Hills, CA > > > > > > > > On Sat, Oct 31, 2009 at 2:35 PM, P & D audvid1@ wrote: > > > > > > > > > > > Thanks you all for the assistance. Got some help today and we climbed > > > under coach and found a ü air line on the driver side front right > behind the > > > fog lights that when you step on the brakes air comes out of that line > and > > > as soon as let off it stops. After looking at drawings and trying to > figure > > > out where the other end should be connected, by accident we discovered > that > > > if you plug the hose, the coach emergency brake released. (Good thing we > > > are on a level lot) and if you un plug it, the emergency brakes stay > > > locked. Then we tried it with the emergency brake released and no air > came > > > out, so I think it is releasing the air bypassing the emergency brake so > as > > > to not release the emergency brake. > > > > > > > > > > > > Hope all that made sense, but it appears that is normal operation, > although > > > I never recall hearing that noise before when I stepped on the brake. > > > > > > > > > > > > Thanks again for all the help > > > > > > > > > > > > Paul & Debbie Potter > > > > > > Hesperia CA > > > > > > 1987 PT 38 > > > > > > Hotel California II > > > > > > > > > > > > *From:* WanderlodgeForum@yahoogroups.com [mailto: > > > WanderlodgeForum@yahoogroups.com] *On Behalf Of *Wayne Kotila > > > *Sent:* Monday, October 26, 2009 1:56 PM > > > *To:* WanderlodgeForum@yahoogroups.com > > > *Subject:* Re: [WanderlodgeForum] Air leaking from front when brakes > > > applied > > > > > > > > > > > > > > > > > > Did you check the rubber hoses to the front brakes? When you step on the > > > brake pedal air pressure applies your front brakes so you will have air > > > pressure in the supply hoses to until you take your foot off the brake > > > pedal. Sometimes from age those hoses will start leaking where the end > is > > > crimped on the hose and if you need to replace them, a farm supply store > > > will carry high pressure hydraulic hose in different diameters and > lengths > > > and have different end adapters to convert the end connector to what you > > > need. You should be able to get a new hose and adapters if needed for > under > > > $20.00. > > > > > > Wayne > > > > > > 1996 WB42 > > > > > > > > > ------------------------------ > > > > > > *From:* ppotter14950 audvid1@ > > > *To:* WanderlodgeForum@yahoogroups.com > > > *Sent:* Sun, October 25, 2009 9:38:25 PM > > > *Subject:* [WanderlodgeForum] Air leaking from front when brakes applied > > > > > > > > > > > > Hi there > > > > > > Today while finishing up Air Force One supplemental braking install for > > > towed vehicle, had engine off and when applied brakes to test Air Force > One > > > and while pedal was depressed there was a constant air leak up front > around > > > the left front area, but could not find it. Any suggestions on where it > > > might be, will work on taking front driver side panel open and looking > in > > > there, but it is so tight in there and i dont know what i am looking for > so > > > any suggestions would be appreciated. > > > > > > Thanks > > > > > > Paul & Debbie Potter > > > 87PT40 - Hotel California II > > > Hesperia CA > > > > > > > > > __________________________________________________ > > > Do You Yahoo!? > > > Tired of spam? Yahoo! Mail has the best spam protection around > > > http://mail.yahoo.com > > > > > > > > > > > > Air leaking from front when brakes applied - gregory O - 11-02-2009 18:00 --- In WanderlodgeForum@yahoogroups.com, "gregory O" > > > slack adjusters on the drive axle got damaged? I believe tcompounding cauld damegd the slack adjusters. the drive is the axle with the park brakes (drive axle has four tires)( Tag has one each side). > Greg > 94ptca > --- In WanderlodgeForum@yahoogroups.com, "P & D" > > > > Wow, that is a bunch of good material, but I may still be confused about the Paul, it kind of makes sense that ;if the service brake is pushed while the spring brake blatter is empty (spring pushing on the brake pad) air will be also sent to the spring brake blatter to lift its force off of the shoe which is now feeling the service brake force?????? But I have no idea of what it should do and how the air is evacuated once again when you release the service brake I would check with an expert shop >> Also when I plugged the hose, the spring brake > > released, is that what you want it to do if you have applied the brakes. > > > > > > > > Thanks for all the info too > > > > > > > > Paul > > > > 87pt38 > > > > Hesperia CA > > > > > > > > From: WanderlodgeForum@yahoogroups.com > > [mailto:WanderlodgeForum@yahoogroups.com] On Behalf Of gregory O > > Sent: Sunday, November 01, 2009 7:21 PM > > To: WanderlodgeForum@yahoogroups.com > > Subject: [WanderlodgeForum] Re: Air leaking from front when brakes applied > > > > > > > > > > > > it is the anti compouning valve blowing air ?? when the spring brake is > > left pushing (park brake on) and someone pushes on the service brakes, the > > valve proportions the pressure working the cams on the axle that hold the > > spring brakes so there is not too much pressure on the shoes. if the valve > > is crapped out you get broken shoes with no sign of heat that made the > > cracks . > > > > > > to keep from giving a lecture then getting a lecture from the mods, check > > <http://www.wsafc.org/WSFMA/Shared%20Documents1/Bendix%20Air%20Brake%20Handb > > ook.pdf> out page 27 of Bendix handbook > > > > > > http://www.wsafc.org/WSFMA/Shared%20Documents1/Bendix%20Air%20Brake%20Handbo > > ok.pdf > > > > here is a good video of <http://www.youtube.com/watch?v=qJa5-_ExsBE> the > > principles of AB without much of the new safety crap confusing the process > > it is from 1967 > > > > http://www.youtube.com/watch?v=qJa5-_ExsBE > > > > Greg > > 94ptca > > > > > > --- In WanderlodgeForum@yahoogroups.com, Curt Sprenger > > wrote: > > > > > > Paul, > > > > > > What you found and determined does not seem right. Post pictures if you > > can. > > > I looked under our coach this afternoon. I see a 1/8" plastic air line to > > > the cylinder that rotates down the driving light. Above that area on the > > > bottom of the frame rail there are some copper and plastic air lines. None > > > are open as you describe. > > > > > > Curt Sprenger > > > 1987 PT38 8V92 "MacAttack Racing" > > > Anaheim Hills, CA > > > > > > > > > > > > On Sat, Oct 31, 2009 at 2:35 PM, P & D audvid1@ wrote: > > > > > > > > > > > > > > > Thanks you all for the assistance. Got some help today and we climbed > > > > under coach and found a ü air line on the driver side front right > > behind the > > > > fog lights that when you step on the brakes air comes out of that line > > and > > > > as soon as let off it stops. After looking at drawings and trying to > > figure > > > > out where the other end should be connected, by accident we discovered > > that > > > > if you plug the hose, the coach emergency brake released. (Good thing we > > > > are on a level lot) and if you un plug it, the emergency brakes stay > > > > locked. Then we tried it with the emergency brake released and no air > > came > > > > out, so I think it is releasing the air bypassing the emergency brake so > > as > > > > to not release the emergency brake. > > > > > > > > > > > > > > > > Hope all that made sense, but it appears that is normal operation, > > although > > > > I never recall hearing that noise before when I stepped on the brake. > > > > > > > > > > > > > > > > Thanks again for all the help > > > > > > > > > > > > > > > > Paul & Debbie Potter > > > > > > > > Hesperia CA > > > > > > > > 1987 PT 38 > > > > > > > > Hotel California II > > > > > > > > > > > > > > > > *From:* WanderlodgeForum@yahoogroups.com [mailto: > > > > WanderlodgeForum@yahoogroups.com] *On Behalf Of *Wayne Kotila > > > > *Sent:* Monday, October 26, 2009 1:56 PM > > > > *To:* WanderlodgeForum@yahoogroups.com > > > > *Subject:* Re: [WanderlodgeForum] Air leaking from front when brakes > > > > applied > > > > > > > > > > > > > > > > > > > > > > > > Did you check the rubber hoses to the front brakes? When you step on the > > > > brake pedal air pressure applies your front brakes so you will have air > > > > pressure in the supply hoses to until you take your foot off the brake > > > > pedal. Sometimes from age those hoses will start leaking where the end > > is > > > > crimped on the hose and if you need to replace them, a farm supply store > > > > will carry high pressure hydraulic hose in different diameters and > > lengths > > > > and have different end adapters to convert the end connector to what you > > > > need. You should be able to get a new hose and adapters if needed for > > under > > > > $20.00. > > > > > > > > Wayne > > > > > > > > 1996 WB42 > > > > > > > > > > > > ------------------------------ > > > > > > > > *From:* ppotter14950 audvid1@ > > > > *To:* WanderlodgeForum@yahoogroups.com > > > > *Sent:* Sun, October 25, 2009 9:38:25 PM > > > > *Subject:* [WanderlodgeForum] Air leaking from front when brakes applied > > > > > > > > > > > > > > > > Hi there > > > > > > > > Today while finishing up Air Force One supplemental braking install for > > > > towed vehicle, had engine off and when applied brakes to test Air Force > > One > > > > and while pedal was depressed there was a constant air leak up front > > around > > > > the left front area, but could not find it. Any suggestions on where it > > > > might be, will work on taking front driver side panel open and looking > > in > > > > there, but it is so tight in there and i dont know what i am looking for > > so > > > > any suggestions would be appreciated. > > > > > > > > Thanks > > > > > > > > Paul & Debbie Potter > > > > 87PT40 - Hotel California II > > > > Hesperia CA > > > > > > > > > > > > __________________________________________________ > > > > Do You Yahoo!? > > > > Tired of spam? Yahoo! Mail has the best spam protection around > > > > http://mail.yahoo.com > > > > > > > > > > > > > > > > > > Air leaking from front when brakes applied - Curt Sprenger - 11-03-2009 02:24 Paul, Do this test...Parking brake set to PARK...get air brake pressure to max...shut off the engine or auxiliary air compressor...step on the service brake pedal...does air expel?..air expelling is good. Repeat stepping on the service brake pedal...until air stops expelling...air brake gauge should be at or below 90 psi...no air expelling is good. Test complete, system is working.ààGreg, you agree? Curt Sprenger 1987 PT38 8V92 "MacAttack Racing" Anaheim Hills, CA On Mon, Nov 2, 2009 at 7:13 PM, P & D <"audvid1@gte.net"> wrote:
Air leaking from front when brakes applied - P & D - 11-03-2009 12:26 That is what it is doing, parking brake on and full of air, when I did not run air down to see if it stopped, but if I turn park I am starting to think that is normal? Paul 87PT38 ââ¬â Hotel California II Hesperia CA From: Paul, Do this test...Parking brake set to PARK...get air brake pressure to max...shut off the engine or auxiliary air compressor...step on the service brake pedal...does air expel?..air expelling is good. Repeat stepping on the service brake pedal...until air stops expelling...air brake gauge should be at or below 90 psi...no air expelling is good. Test complete, system is working. Greg, you agree? Curt Sprenger 1987 PT38 8V92 "MacAttack Racing" Anaheim Hills, CA On Mon, Nov 2, 2009 at 7:13 PM, P & D <"audvid1@gte.net"> wrote: Wow, that is a To add more to Thanks for all Paul 87pt38 Hesperia CA From: "WanderlodgeForum@yahoogroups.com" [mailto:"WanderlodgeForum@yahoogroups.com"] it is the anti compouning valve blowing air Air leaking from front when brakes applied - Don Bradner - 11-03-2009 14:39 I think you would find that, if you blocked that hose, you couldn't set the parking brake at all. I know just enough about this to be dangerous, so take this as a general thought rather than expert opinion. It is based on having replaced my parking valve and looking at the drawiings of how it works. There are 3 ports on the parking valve. Air source, Air delivery, and Air exhaust. Its "normal" at rest position (pushed by a spring) would have air running from source to delivery and spring brake applied. When you push in and overcome that spring, air pressure keeps it closed with air running from source to delivery, which holds the spring brake off. If air pressure drops below the spring value, the switch pops to its resting position. When the air is allowed to exhaust, another valve in the system opens, called a Quick Release valve. The line running to the dash is not large enough to truly exhaust the air quickly from the chambers - that happens at the QR valve. When you step on the brakes, I'm guessing the QR-valve expels additional air and you get expelling air out to the exhaust. When you block the exhaust, the air now coming in opens the valve allowing air to pass to the parking brake, thus releasing it. On my coach, the exhaust line runs out through the dash, and I did not trace it, but it makes sense that it would go down somewhere in front. This line is not required, but otherwise you get more air noise in the cab. On 11/3/2009 at 4:26 PM P & D wrote: >That is what it is doing, parking brake on and full of air, when I step >on brake pedal, I hear air expelling from hose. I had never heard that >before (it probably was doing it) > > > >I did not run air down to see if it stopped, but if I turn park brake off >(push knob in) then there is no air expelled from hose. > > > >I am starting to think that is normal? |