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Author Topic: air leak or normal sound  (Read 2729 times)
white-eagle
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« on: August 10, 2008, 05:04:24 PM »

my brake light has been staying on, so i parked it on a slight incline to see if something was dragging.  rolled very easily,so i guess no brake drag.  as long as it was stopped, i walked around and noticed that it sounded like an airleak around the drive axle, near the rear air tank.  a strong leak sound.  then engine was running, and showing about 100lbs on the gauge
then when i had my copilot set the park brake, it stopped.

i couldn't see where the leak was exactly, and maybe it's normal to be blowing air out while stopped, no park brake set, engine and compressor running.  i'm just not usually near the duals without the brake being set.

i'm assuming the brake warning light staying on after the park brake is release, is a short in the light?  which i'm going to fix in the next week b4 the next trip.
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Tom
1991 Eagle 15 and proud of it.
8V92T, 740, Fulltime working on the road.

Fran was called to a higher duty 12/16/13. I lost my life navigator.
luvrbus
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« Reply #1 on: August 10, 2008, 05:28:05 PM »

Tom that is not normal it is your automatic drain,the e6 valve or the sr1 valve leaking
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Busted Knuckle
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« Reply #2 on: August 10, 2008, 06:40:15 PM »

Tom that is not normal it is your automatic drain,the e6 valve or the sr1 valve leaking

Also the leak could be causing the lights to stay on , by lack of pressure to the switch.  Grin  BK  Grin
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« Reply #3 on: August 10, 2008, 07:27:13 PM »

the pressure goes to 120lbs although i noticed while driving that it drops to 90 or so, then builds back up.  i assumed it was the normal pressure air spit that you hear periodically.  it's not a steady leak in that it maintains pressure for a while, not losing everything for about 5 days to get down to 20lbs while parked.

everything seems to be working, just made me a litlle nervous when i heard what sounded like an airleak.  stopped when we applied the park brake or turned the engine off.  i know it stopped.  no air was lost after engine stopped, at least not immediately and you couldn't hear it, even with the park brake off although pressure still up.
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Tom
1991 Eagle 15 and proud of it.
8V92T, 740, Fulltime working on the road.

Fran was called to a higher duty 12/16/13. I lost my life navigator.
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« Reply #4 on: August 10, 2008, 07:55:29 PM »

Tom,
I'm not sure what kind of braking system you have on your Eagle but it sounds like you may have a parking brake diaphragm failing. If that is the case, it will get worse until it fails completely leaving you somewhere with your brakes locked.

Have your mechanic check it out.

TOM
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makemineatwostroke
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« Reply #5 on: August 10, 2008, 08:08:24 PM »

could be a diaphragm or the or the SR1 valve relay itself needs to be repaired or what Tom said will happen when you apply the parking brake one day it will not release and it works your compressor twice as hard
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TomC
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« Reply #6 on: August 10, 2008, 08:19:39 PM »

What can sometimes happen is that the parking brake diaphragm will get a leak in it-the leak you hear when the parking brake is "released" and no sound when it is set (because it uses air pressure to release the spring brakes, so you have spring braking if you run out of air pressure all together).  And then the leak can get into the service brakes-if that diaphragm has a small hole in it it can back flow into the brake system not allowing all the air out of the system, hence the stop light staying on since it is activated by air pressure.  Just get a whole new parking/service brake can-they're less than $200 and it isn't worth the hassle or safety issues to try to rebuild the old one.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
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« Reply #7 on: August 10, 2008, 08:21:45 PM »

If its the emergency side diaphram it will not offset the spring brake. That will allow the shoes to drag the drums going down the road. When this happens the brake drum gets cherry red and blows the tires out. When you stop, the drums will start the tires on fire and it will burn.

Most emergency side diaphrams are permently banded to prevent the spring brake from injuring someone. A piggyback is under $100 and easy to change. You may have 30-30 or 30-36 chambers. I have seen them mixed and would let someone else argue that, however a 30-30 is very common and will get you home, even if you have 30-36 chambers.
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white-eagle
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« Reply #8 on: August 10, 2008, 08:25:03 PM »

some of what you've commented does not sound correct if i play it back in my head, which is also where a problem might be.
rk
let me be clearer.  the air leak sound only is there when the engine is running and the brake is off.  if i put the park brake on, then the sound goes away, no air leak.  if i stop the engine, no air leak.  if i have the engine running and no brake set, no brake on at all, just sitting there on level ground not moving at all, then i hear an airleak.

i wasn't where i had time or capability to get under the axle yet, so i'm not sure of the source of the "leak".

i don't understand at this point how the park brake diaphram is leaking if it's not on?  obviously, i'm cornfused (as Grandpa Jones used to say).
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Tom
1991 Eagle 15 and proud of it.
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Fran was called to a higher duty 12/16/13. I lost my life navigator.
white-eagle
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« Reply #9 on: August 10, 2008, 08:31:10 PM »

i just read the 2 posts prior to mine.  now it makes a little more sense and thanks for all the posts.  i'm sure what doesn't make sense to me is due to lack of understanding which is why i replied to BK's earlier post about a training class.

the last thing i want to do is have a brake failure!

let me rephrase.  i don't want a brake failure to be the last thing i or anyone else with me experiences.
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Tom
1991 Eagle 15 and proud of it.
8V92T, 740, Fulltime working on the road.

Fran was called to a higher duty 12/16/13. I lost my life navigator.
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« Reply #10 on: August 10, 2008, 08:34:24 PM »

When the parking brake is "off" it is charged with 120psi air to push the diaphragm back off the big spring inside to release the brakes.  You have a hole in the parking brake diaphragm.  When you release or set the parking brakes, this is why you hear the big air release-it is the 120psi air pressure being released out of the parking brake so the big spring inside can set the brakes.  Once again-check your parking brake cans.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
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« Reply #11 on: August 10, 2008, 09:16:47 PM »

Get a spray bottle of dish soap and water and spray every thing down and you will get lots of bubbles at the leak. I am so deaf I do this once in a while just to check the system.
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JackConrad
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« Reply #12 on: August 11, 2008, 05:07:22 AM »

    First, we need to determine if Tom has Spring Brakes or DD3s. There is a difference in how they are plumbed and how they operate.
    Tom, look at the brake can on your drive axle and see if it has 2 or 3 hoses attached to it. 2 hoses=Spring Brake, 3 hoses=DD3.  Jack
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« Reply #13 on: August 11, 2008, 05:43:55 PM »

2 hoses going to the can with a shaft out the bottom going to an arm on the wheel drum.  there is a rubber hole cover on top of the can that was off.  didn't look like anything other than an access hole with a dust cap, just that the cap wasn't on. 
checking it out with the help of Redbus on the phone.  i'm blaming him for getting my good shirt dirty since i had to check it right away instead of changing shirts first.

guess i'm gonna hafta read the manual cuase the class won't be soon enough.

thanks jack for the tip.
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Tom
1991 Eagle 15 and proud of it.
8V92T, 740, Fulltime working on the road.

Fran was called to a higher duty 12/16/13. I lost my life navigator.
luvrbus
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« Reply #14 on: August 11, 2008, 05:55:57 PM »

Tom, don't know if you noticed or not but there is a grease zert on each one of those cans that needs to be greased often
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