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valleybusman
Top Member
USA
798 Posts |
Posted - 02/01/2020 : 1:05:48 PM
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The last couple years we have been plagued by air leaks . These have caused issues in our inspections . A lot of buses the driver will park and in a few hours or over night the low air buzzer will come on and the air pressure will be down to 60 or less lbs .I always used a mix of soap and water sprayed at fittings . Is this still the standard or is there another way that is better .My boss is worried our buses will be placed OS when inspected . Thanks |
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ACL
Senior Member
USA
53 Posts |
Posted - 02/01/2020 : 1:43:21 PM
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To me it’s odd that this can even show self as a problem as we always pump the brakes down when parking for any extended period, so we have no expectation that the buses will hold air pressure for hours on end. On my bus, the separate air reservoir for the door is always depleted overnight.
Our state requirement for pressure loss is two PSI per minute with the parking brake off, three with the service brake applied. Do you have a stricter requirement?
I have experienced air leakage in the front door system. |
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valleybusman
Top Member
USA
798 Posts |
Posted - 02/02/2020 : 6:46:30 PM
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Ours the same but my boss feels a 60 pound loss in 12 hours is too much . The newer buses drop only 5 or 10 pounds we have had issue during inspections where they have dropped 5 lbs in 1 minute and the bus was placed OS so we are a little paranoid the air loss has been the ABS relays |
Edited by - valleybusman on 02/03/2020 11:05:38 AM |
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Thomasbus24
Administrator
USA
4544 Posts |
Posted - 02/03/2020 : 04:57:29 AM
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Pre-mixed bottle of simple green is my go-to. It foams/bubbles well.
The PPDC parking valve and the valve that runs the back brakes over the axle...number escapes me right now...but those are our two frequent leakers. |
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Bluenozer
Top Member
Canada
640 Posts |
Posted - 02/03/2020 : 07:53:10 AM
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Even brand new trucks at the dealer ship do the same get rid of push lock connectors they all will leak after time i tell drivers they are made to lose air to ensure the operator does a proper warm up before leaving the yard. Our inspectors only care about real leaks , brake can, air bag, things that he can hear while inspecting , but air loss(non-audible) over night that hurts no one |
OEM trained in wiring and all engine platforms for over 20 years
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ACL
Senior Member
USA
53 Posts |
Posted - 02/03/2020 : 08:11:58 AM
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"... my boss feels a 60 pound loss in 12 hours is too much . The newer buses drop only 5 or 10 pounds we have had issue during inspections where they have dropped 5 lbs in 1 minute"
There's a HUGE difference between 5 per minute and 60 in twelve hours! One is out of spec and the other is probably unrealistically good. I checked this morning and while I was parked between runs I lost an estimated 8 psi in 15~20 minutes. So, roughly half a psi per minute; well within spec yet it would almost certainly be under 60 after 12 hours. |
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exmod110
Senior Member
150 Posts |
Posted - 02/03/2020 : 12:53:00 PM
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When I worked with air brake systems, we used an ultra sonic leak detector. Basically a mic and headphones tuned to the sound of an air leak. Point the mic end towards any valve or fitting in question and even a small leak could be herd clear as day. It was real beneficial to the people with hearing loss or for valves in places you can not get close to with ur ear. |
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Gearbox
Senior Member
USA
53 Posts |
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dferrell
Senior Member
102 Posts |
Posted - 02/04/2020 : 09:08:15 AM
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60 lbs in 12 hrs isn't bad at all. As long as the air loss is less than the legal amount, you are fine. No repair needed. Like the others, here it is 2 lbs/min unapplied and 3 lbs/min applied. I normally use soapy water but have also bought regular bubbles (for kids to blow bubbles), for real small or stubborn leaks. |
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CISDbusman
Advanced Member
305 Posts |
Posted - 02/06/2020 : 06:52:25 AM
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A piece of 3' rubber fuel line stuck to your ear works pretty good if you don't have the budget for the high end tools. It will flex around this and that on the chassis chasing leaks.
I quiet shop works well too.....
Best of luck!! |
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