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Author Topic: air leak or normal sound  (Read 2557 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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Busted Knuckle aka Bryce Gaston
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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.
8V92T, 740, Fulltime working on the road.

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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white-eagle
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« Reply #15 on: August 11, 2008, 06:29:31 PM »

had all zerts greased last year, about 8000 mi ago, by the neighbor farmer's grandson who's taking diesel mechanics.   Smiley

 Undecided more often?
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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.
Busted Knuckle
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« Reply #16 on: August 11, 2008, 07:14:20 PM »

had all zerts greased last year, about 8000 mi ago, by the neighbor farmer's grandson who's taking diesel mechanics.   Smiley
 Undecided more often?

Yes! Atleast once or trice a yr! (depending on how many miles you run!) And every 3-4,000 miles the whole thing should be lubed! JMHOFWIW! (add $5 and you'll have enough for a gallon of fuel!)  Grin  BK  Grin
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Busted Knuckle aka Bryce Gaston
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« Reply #17 on: August 11, 2008, 08:59:12 PM »

uh-oh.  i guess this shows ignorance again???  sorry guys, i just didn't read that manual front to back.  thanks for the heads up bk and lvrbus.
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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 #18 on: August 12, 2008, 07:04:33 AM »

On my first truck with the 8V-92TA-I would lube the chassis at oil change time which was every 10,000 miles.  But would lube the the king pins 2 times inbetween since I didn't have power steering.  With my present truck, I just lubed and changed the oil at 12,000 mile intervals and was enough since I replaced my first U joint at 800,000 miles.  My king pins would last 500,000 miles.  It's amazing how long chassis components will last if you just grease them.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
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« Reply #19 on: August 12, 2008, 09:07:10 AM »

On my first truck with the 8V-92TA-I would lube the chassis at oil change time which was every 10,000 miles.  But would lube the the king pins 2 times inbetween since I didn't have power steering.  With my present truck, I just lubed and changed the oil at 12,000 mile intervals and was enough since I replaced my first U joint at 800,000 miles.  My king pins would last 500,000 miles.  It's amazing how long chassis components will last if you just grease them.  Good Luck, TomC

Tom on my trucks (all had either 60 series or CAT's) I did oil changes at 12,000 and did complete chassis lubes (trk & trlr) every 4,000 hardly ever had problems. Can't ever replacing a U-joint in one (not one I personally maintained anyway), I did have a U-joint go out on one trk shortly after purchasing it used.(found out later the driver was getting fake shop receipts and pocketing the $) Never had problems with tie rod ends, king pins, slack adjusters, or any of that stuff. I carried a creeper, cover alls, grease gun and lots of tools so I kept my personal trk in top shape. Had drivers that did it both ways some would take care of their own and get $50 from me each time they "serviced it", and others would pull into Speedco, Petro, Flying Hook, etc. and turn in the reciept. Of course then there was the driver that walked home from Chula Vista, CA (or however he got back to Oklahoma I didn't care. But the girlfriend and I left him standing in the receivers parking lot next to a pile of all his stuff once she discovered his a bunch reciepts were fake. She drove our trk, I drove his!) Grin  BK  Grin
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Busted Knuckle aka Bryce Gaston
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Grin Keep SMILING it makes people wonder what yer up to! Grin (at least thats what momma always told me! Grin)
makemineatwostroke
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« Reply #20 on: August 12, 2008, 10:25:05 AM »

Eagle buses call for grease every 6000 miles according to the book I do 5000 miles the Eagle front suspension has more moving parts than a straight axle with air bags
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belfert
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« Reply #21 on: August 12, 2008, 01:14:23 PM »

I drive my bus anywhere from 4,000 to 7,000 miles a year depending on event locations that year.  I get the oil changed and chassis lubed once a year.  I take it to a bus garage as they have a lift so they can check everything out real good underneath.
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white-eagle
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« Reply #22 on: August 12, 2008, 05:28:01 PM »

my apologies (again)  Embarrassed.  i should have gotten underneath before i posted anything, but i was hoping someone would say that sound is normal and i wouldn't have to get under the bus.

there is a hose from each side's spring brake can that goes to a valve mounted on the front center of the drive axle.  i think they are 1/2" hoses.  at the top of the distribution valve there is a slightly larger hose coming out the top.  IT HAS A BIG HOLE!

i misled everyone when i said it didn't leak when i shut the air off.  it does leak, unless you have the park brake set, which i usually do.  obviously, that hose is only full of air when the engine is running and the park brake is not set.  as in most of the time i'm driving down the road making my compressor work it's butt off.

i guess i'm lucky i'm too lazy to apply the park brake on flat ground when i unhooked the tow van because i'd have not found the leak until the hole got so large that the brake set in the middle of the turnpike on my next trip becuase we ran out of air.

i'll be taking the hose off and trying to figure out why it developed a hole, then replacing it with a new piece, inspecting other hoses for bad spots.

ohh, and while i'm there, i'll grease up a few spots.

thanks for the suggestions.

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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.
oldmansax
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« Reply #23 on: August 12, 2008, 07:18:34 PM »

Hoses are usually easier to replace than brake parts!   Grin

Glad you found the problem    Smiley Smiley

TOM
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« Reply #24 on: August 12, 2008, 08:39:54 PM »

Easy test for air integrity for every busnut:

Aired up, shut engine off, parking brake released, foot brake held to the floor.

Watch the needles, and listen.

Needles stay still and silence, you have no leaks.

trouble shooting is doing each step alone and checking as you go.

happy coaching!
buswarrior
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JackConrad
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« Reply #25 on: August 13, 2008, 05:13:38 AM »

Tom,
    Take to hose to a large truck parts store. They should have what you need. Some of the hoses have re-useable end pieces. The parts store person should be able to help you figger all this out.  Jack
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