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08-04-2020, 10:15 AM
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#1
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Senior Member
Join Date: Feb 2017
Location: Somewhere New!
Posts: 181
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Brake Check Freightliner XCR - Two Tank System
I've got a new 2020 Dutch Star 3717 on a Freightliner XCR that we took delivery of a couple of weeks ago. It's got two air tanks. When performing the brake check per the below instructions, Tank #1 operates as it should, per the last bullet in bold, with little to no pressure loss. However, Tank # 2 looses pressure very quickly and continues to decline until the service brake is released. I've read the Freightliner manual, researched on their site and online but I can't find if this is normal for a two tank system or not.
The coach was driven from Newmar to my dealer in CA, that's about 100 miles away, then back and forth to Reno a few times. I also took it for a 1 hour drive Saturday. It has over 2,500 miles and about 250 to 300 since arriving at the dealer. Brakes seemed to operate just fine since arriving at the dealer and maintained pressure, etc while in normal operating mode.
Looking for input on testing a two tank system and if my results are normal.
Here's the test I'm performing:
• Chock the wheels.
• With the engine running, build the air pressure to governed cut-out (100-125 psi).
• Shut off the engine, turn key to ON position.
• If necessary, release the tractor protection valve and parking brake, push in valves.
• Fully apply the foot brake and hold it for one minute.
• Check the air gauge to see if the air pressure drops more than three pounds in one minute (single vehicle) or four pounds in one minute (combination vehicles).
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08-04-2020, 10:31 AM
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#2
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Senior Member
Join Date: Aug 2015
Posts: 856
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so your saying with the Spring Brake released (parking brake) and holding your foot on the brake pedal, air pressure drops in tank #2 until the parking break engages.
that s a leak
you have your 2 tanks. 1- is for front brakes and 1- is for rear...however they are sectioned off and you most likely have 4 chambers called ping tanks(wet tanks)...1 in in each tank that feeds your airbags
I have attached an air diagram from Freight Shaker to help you understand a bit better of what you have.
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08-04-2020, 10:34 AM
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#3
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Senior Member
Join Date: Apr 2011
Location: Powell River, B.C.
Posts: 31,311
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Ok your two tank system as it relates to your brakes on an air system . One tank supplies air to the front brakes , the second supplies air to the rear brakes .
From one of the tanks , air is supplied to other air system items , air suspension , air horns , in the case of my chassis air activated exhaust brake.
Call Freightliners free help line for an " air system diagram " that will help determine which tank relates to which system.
1-800-385-4357 Have your serial number handy.
Have a helper hold the service brake pedal down while you do a walk around ,of the coach , if you hear air leaking then you could have a warranty repair required.
Unfortunately , after the bare chassis left Freightliner , I'll bet the system was never rechecked using this method. So an air line could have been damaged on the coach manufacturers assembly line.
__________________
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.
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08-04-2020, 10:36 AM
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#4
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Senior Member
Join Date: Aug 2015
Posts: 856
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Quote:
Originally Posted by Skip426
Ok your two tank system as it relates to your brakes on an air system . One tank supplies air to the front brakes , the second supplies air to the rear brakes .
From one of the tanks , air is supplied to other air system items , air suspension , air horns , in the case of my chassis air activated exhaust brake.
Call Freightliners free help line for an " air system diagram " that will help determine which tank relates to which system.
1-800-385-4357 Have your serial number handy.
Have a helper hold the service brake pedal down while you do a walk around ,of the coach , if you hear air leaking then you could have a warranty repair required.
Unfortunately , after the bare chassis left Freightliner , I'll bet the system was never rechecked using this method. So an air line could have been damaged on the coach manufacturers assembly line.
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you replied while I was attaching....
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08-04-2020, 10:38 AM
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#5
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Senior Member
Join Date: Apr 2011
Location: Powell River, B.C.
Posts: 31,311
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Quote:
Originally Posted by Wild Card
you replied while I was attaching....
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Happens way more often than you'd think . I've tied on posting several times.
EDIT: Important to have the correct air system diagram , tied to your serial number .
__________________
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.
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08-04-2020, 11:42 AM
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#6
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Senior Member
Join Date: Jul 2014
Posts: 35,349
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Quote:
Originally Posted by Wild Card
so your saying with the Spring Brake released (parking brake) and holding your foot on the brake pedal, air pressure drops in tank #2 until the parking break engages.
that s a leak
you have your 2 tanks. 1- is for front brakes and 1- is for rear...however they are sectioned off and you most likely have 4 chambers called ping tanks(wet tanks)...1 in in each tank that feeds your airbags
I have attached an air diagram from Freight Shaker to help you understand a bit better of what you have.
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No ping tanks, only one wet tank, a section of a service tank, and 2 service tanks.
The wet tank receives the air from the compressor and sends it to the 2 service tanks. They supply all of the air functions.
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08-04-2020, 12:14 PM
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#7
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Senior Member
Join Date: Feb 2017
Location: Somewhere New!
Posts: 181
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Thanks guys.
I've got a call into Freightliner help line as a first step and that'll likely lead to a service appointment.
Before scheduling, I'm also going to repeat the test just to ensure I did it correctly. It was my first time doing an air brake test. I did it Saturday AM, was watching a video training session on air brakes and the test was part of that training session. The instructions I posted came from Nevada's non-commercial Class B training manual and could be different than what I actually did but they seem the same. That said I don't clearly remember the exact sequence I went through on the video Saturday AM so I may have done something incorrectly, compared to what I posted above. In any case now that I understand the system better it'll make more sense and the step by step written instructions will ensure I execute it properly.
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08-04-2020, 07:50 PM
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#8
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Senior Member
Join Date: Feb 2017
Location: Somewhere New!
Posts: 181
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Update:
I have no idea what I did the first time but I’ve repeated the test three times and everything is fine! I did call Freightliner and within a couple hours a very nice and helpful gentleman returned my call so it seems they have top notch service.
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