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12-13-2017, 06:42 AM
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#1
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Senior Member
Join Date: Jun 2014
Location: Buffalo, NY
Posts: 135
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Air Pressure Drops 20psi With Every Brake Application 05 Diplomat...
Hello friends,
I have been experiencing a strange issue with my 2005 Monaco, lately when I start it the air pumps up as usual. Once it reaches 130 PSI and the bags have pumped up I put it into gear. All is well until I apply the service brakes, the pressure drops dramatically, sometimes to 90psi or lower and it causes the low pressure alarm to come on.
I can hear a significant amount of air being released when I lift the pedal. This has never happened in the past. The air system holds pressure well otherwise, it only drops when braking (I know this is normal to some extent, but it seems extreme all the sudden).
I can dump the whole system by pumping the pedal 4 or 5 times.
Thoughts???
__________________
Dan
2005 Monaco Diplomat 40 PDQ
8.9L Cummins ISL 400
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12-13-2017, 06:45 AM
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#2
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Senior Member
Join Date: Jun 2011
Location: FL
Posts: 11,386
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Welcome to the forum. Sorry but can't help but sure want to follow this one. There is plenty of knowledge here and someone will nail it shortly.
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Certified Senior Electronic Technician, Telecommunications Engineer, Telecommunications repair Service Center Owner, Original owner HR 2008
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12-13-2017, 06:48 AM
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#3
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Senior Member
Monaco Owners Club
Join Date: Aug 2015
Location: Elgin, SC
Posts: 106
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I would be checking the brake air lines front and rear. Also check the air dryer. Sometimes the air purge valve will stick open. Hope this helps.
__________________
Butch & Jo
Retired Marine/Department of Defense
2017 Monaco Diplomat
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12-13-2017, 06:51 AM
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#4
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Senior Member
Join Date: Jun 2014
Location: Buffalo, NY
Posts: 135
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Quote:
Originally Posted by devildawg
I would be checking the brake air lines front and rear. Also check the air dryer. Sometimes the air purge valve will stick open. Hope this helps.
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Thanks for the reply. I had thought of the dryer/purge valve. Wouldn't a problem there cause a constant leak? I'm only losing air after applying the brakes.....
__________________
Dan
2005 Monaco Diplomat 40 PDQ
8.9L Cummins ISL 400
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12-13-2017, 06:55 AM
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#5
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Senior Member
Monaco Owners Club
Join Date: Aug 2015
Location: Elgin, SC
Posts: 106
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True! Sometimes the valve will stick just enough to allow air to escape. Have someone apply the brakes while you’re listening outside. It got to be loud to allow that amount of air to escape.
__________________
Butch & Jo
Retired Marine/Department of Defense
2017 Monaco Diplomat
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12-13-2017, 07:02 AM
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#6
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Junior Member
Holiday Rambler Owners Club
Join Date: Jan 2014
Location: Canada
Posts: 13
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I hate to be the voice of reason to rain on your parade and bring you bad news, especially at this time of year on such a beautiful day.
It sounds like a bad treadle or ratio valve leak. This can be a serious issue please have it inspected.
FYI:
https://airbrakeinfo.wordpress.com/2...-it-can-cause/
Happy travels
Good luck
__________________
Canadian Voluntourist
'05 HR Navigator 43PBQ
Life's short, play naked.
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12-13-2017, 07:04 AM
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#7
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Member
Monaco Owners Club Vintage RV Owners Club
Join Date: Oct 2017
Location: Arizona
Posts: 92
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Don't drive it!
You likely have a cracked or broken brake air line on your rig. Call a mobile truck repair company to come out and inspect your lines. You definitely have a leak AFTER the brake pedal on your service brakes and is a serious drivability issue. Your emergency brakes will engage at approximately 20psi and you will not be able to move the coach until your air pressure resumes.
You may also be 'dragging' a drum brake pad if an air line is severed from the brake chamber.
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12-13-2017, 07:09 AM
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#8
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Member
Join Date: Nov 2015
Posts: 71
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slow down
Ok if You had a leak the psi would just keep going down when holding the brake pedal in place . It sounds like to Me the brake shoes are just out of adjustment . Think a bout what is happening when the brake is pushed the shoes have to move farther to hit the drums , so it takes more air . the adjustment can be made with out removing the wheels and is no big deal .
when was the last time you had the brakes adjusted . on a truck the adjustment is part of the normal dot insp
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12-13-2017, 07:09 AM
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#9
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Member
Monaco Owners Club Vintage RV Owners Club
Join Date: Oct 2017
Location: Arizona
Posts: 92
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Further: you will not be able to detect an air leak with your parking brake engaged. If you wish to look for it yourself, CHOCK YOUR WHEELS, release your parking brake and depress the service brake, you may be able to identify where the air leak is by walking around the coach. DO NOT crall uner the coach with the parking brake released.
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12-13-2017, 07:21 AM
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#10
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Senior Member
Join Date: Mar 2017
Posts: 671
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If you are losing that much air while the brakes are being applied you have a bad brake Biscuit, that is the diaphragm that applies the brake when pressure is applied. You can check which one is leaking by going outside and someone else apply the brake while you listen. More than likely it will be on the rear axel. Press and hole the brake pedal, if the pressure goes way down to cause the buzzer and or the low pressure light to come on your unit has a bad leak and is not safe to drive.
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12-13-2017, 07:34 AM
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#11
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Senior Member
Join Date: Jun 2014
Location: Buffalo, NY
Posts: 135
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Quote:
Originally Posted by nash2014
I hate to be the voice of reason to rain on your parade and bring you bad news, especially at this time of year on such a beautiful day.
It sounds like a bad treadle or ratio valve leak. This can be a serious issue please have it inspected.
FYI:
https://airbrakeinfo.wordpress.com/2...-it-can-cause/
Happy travels
Good luck
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No worries it's off the road for the winter, it's parked in the parking lot where I work (a major RV service center). I will have it looked at before it's driven again. Was hoping to gain some knowledge before I have it looked at.
__________________
Dan
2005 Monaco Diplomat 40 PDQ
8.9L Cummins ISL 400
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12-13-2017, 07:36 AM
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#12
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Senior Member
Join Date: Jun 2014
Location: Buffalo, NY
Posts: 135
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Quote:
Originally Posted by n2587n
Ok if You had a leak the psi would just keep going down when holding the brake pedal in place . It sounds like to Me the brake shoes are just out of adjustment . Think a bout what is happening when the brake is pushed the shoes have to move farther to hit the drums , so it takes more air . the adjustment can be made with out removing the wheels and is no big deal .
when was the last time you had the brakes adjusted . on a truck the adjustment is part of the normal dot insp
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I just spoke with a tech in the shop and they said the same thing, likely just way out of adjustment. They're going to get it in the bay later this week...
__________________
Dan
2005 Monaco Diplomat 40 PDQ
8.9L Cummins ISL 400
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12-13-2017, 07:51 AM
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#13
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Senior Member
Winnebago Owners Club Workhorse Chassis Owner
Join Date: May 2016
Location: Kamloops, BC, 60 miles from the Center of the Universe according to the Rinpoche, of the SF monks.
Posts: 7,305
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Quote:
Originally Posted by MonacoMan84
I just spoke with a tech in the shop and they said the same thing, likely just way out of adjustment. They're going to get it in the bay later this week...
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Sounds like your slacks aren't adjusted. They should be auto adjusting.
Happy Glamping.
__________________
Happy Glamping, Norman & Elna. 2008 Winnebago Adventurer 38J, W24, dozens of small thirsty ponies. Retired after 40 years wrenching on trucks! 2010 Ford Ranger toad with bicycles or KLR 650 in the back. Easy to spot an RVer, they always walk around with a screwdriver or wrench in one hand!
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12-13-2017, 08:18 AM
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#14
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Senior Member
Join Date: Jun 2014
Location: Buffalo, NY
Posts: 135
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Quote:
Originally Posted by Unplanned
Sounds like your slacks aren't adjusted. They should be auto adjusting.
Happy Glamping.
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Yes I do have auto slack adjusters, sometimes I can hear them adjust on a hard brake application, however one of the guys here said they often stick and don't adjust properly. I will report what I find when we get it in the shop.
Thanks again everyone...
__________________
Dan
2005 Monaco Diplomat 40 PDQ
8.9L Cummins ISL 400
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