Air leak from transmission area, brake pedal like concrete

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flvet352

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My deuce has been blowing off air from what I believe is the air pack vent line, and now I can hear a leak from under the truck. Somewhere around the transmission area. I didn't have alot of time to pinpoint it today. It will build air and pin the gauge to the right while the truck is running, but within a few minutes of shut off she is out of air. Also, while driving around after the air builds up, the brakes slam on just by tapping the pedal. I can push on it as hard as I can (after I stop) but the pedal will barely go down half an inch. Earlier today, after I stopped at an intersection the light immediately turned green I attempted to pull off but it seemed like the brakes were still engaged for a moment. Could the governor be bad and the air compressor is actually overcharging the system?
 

Dipstick

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Sounds to me like it could be the air unit that the master cylinder is bolted to. It uses the compressed air to assist your pedal effort when braking. I'm not very knowledgeable about this, but there was a thread on here with pictures in which a member showed how to rebuild it. It had a piston with a seal inside. I'm sure some of the smarter guys will respond to you.
 

NY Tom

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I cannot recall the correct air pressure setting but I feel like it is around 120 psi. If your compressor is charging higher than that on the in-cab gauge then try installing another gauge somewhere to check your reading. If it goes too high the governor might be the problem.

If you have a constant leak air from the airpack this is a problem for sure and needs to be investigated.
 

cattlerepairman

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Your air pressure readings are definitely suspect. When the truck builds pressure, is there a point where the compressor unloads (stops producing pressure)?
Or is it pumping constantly? You may have to listen very closely on idle. The governor is a cheap and easy NAPA replacement. Or it could be the dash gauge going wonky. The tip of plumbing a gauge in near the compressor is a good one.

Before assuming the $500 air pack has gone bad, meticulously check the air lines for leaks and snug up the fittings, then re-assess. There are a few failure modes of the pack and master cylinder, such as rock hard pedal and brakes locking up, hydraulic brakes without air assist, constant air leak etc.

The air pack has a valve inside that can stick with all the gunk that accumulates over time. Personally. I am a fan of tapping that area gently but persistently with a hammer and operating the brake rapidly a few times. It may just be enough to get that piece of crud out from where it should not be.

That way you know your air pack needs a disassembling and cleaning but it buys you time to plan for it.
 

frank8003

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Attach service air/instrument air to the right hand rear glad hand.
Compressor far away'
Have soldier "B" operate the brake pedal while one crawls around under truck seeking leaks and mal-functions. Block the wheels and remove the battery tie and be safe.
In this way there is no engine or compressor noise at all. Can do this for hours and hours. In fact if NOT going to run the engine this is a good exercise for the brakes and all brake components. Use proper oil into air pak, check the vent, etc.
 

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flvet352

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Gainesville/Florida
Your air pressure readings are definitely suspect. When the truck builds pressure, is there a point where the compressor unloads (stops producing pressure)?
Or is it pumping constantly? You may have to listen very closely on idle. The governor is a cheap and easy NAPA replacement. Or it could be the dash gauge going wonky. The tip of plumbing a gauge in near the compressor is a good one.

Before assuming the $500 air pack has gone bad, meticulously check the air lines for leaks and snug up the fittings, then re-assess. There are a few failure modes of the pack and master cylinder, such as rock hard pedal and brakes locking up, hydraulic brakes without air assist, constant air leak etc.

The air pack has a valve inside that can stick with all the gunk that accumulates over time. Personally. I am a fan of tapping that area gently but persistently with a hammer and operating the brake rapidly a few times. It may just be enough to get that piece of crud out from where it should not be.

That way you know your air pack needs a disassembling and cleaning but it buys you time to plan for it.
I now remember that my air compressor makes a clicking sound when it is running(I probably need to replace it soon) and when I last drove the truck the clicking sound was constant. It never stopped. So I definitely think the compressor is running constantly. I bought a new air governor at napa today. When I have the time to work on it I will advise how it goes. Thanks.
 

flvet352

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Gainesville/Florida
Your air pressure readings are definitely suspect. When the truck builds pressure, is there a point where the compressor unloads (stops producing pressure)?
Or is it pumping constantly? You may have to listen very closely on idle. The governor is a cheap and easy NAPA replacement. Or it could be the dash gauge going wonky. The tip of plumbing a gauge in near the compressor is a good one.

Before assuming the $500 air pack has gone bad, meticulously check the air lines for leaks and snug up the fittings, then re-assess. There are a few failure modes of the pack and master cylinder, such as rock hard pedal and brakes locking up, hydraulic brakes without air assist, constant air leak etc.

The air pack has a valve inside that can stick with all the gunk that accumulates over time. Personally. I am a fan of tapping that area gently but persistently with a hammer and operating the brake rapidly a few times. It may just be enough to get that piece of crud out from where it should not be.

That way you know your air pack needs a disassembling and cleaning but it buys you time to plan for it.
I replaced the governor today and no more air leaks. I shut the truck off and she holds 120psi. However, now the first time I press the brake pedal (like to put it in gear) it immediately gets rock solid and the truck won't go anywhere because the brakes are locked up. The brake lights are also stuck on (air activated brake switch). I am guessing that the governor was bad and it was overcharging the system and that is why it was venting extra air from anywhere it could. I think it broke the airpack and now that one problem is fixed I have to replace the airpack. Does this sound right?
 

flvet352

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Gainesville/Florida
I replaced the governor today and no more air leaks. I shut the truck off and she holds 120psi. However, now the first time I press the brake pedal (like to put it in gear) it immediately gets rock solid and the truck won't go anywhere because the brakes are locked up. The brake lights are also stuck on (air activated brake switch). I am guessing that the governor was bad and it was overcharging the system and that is why it was venting extra air from anywhere it could. I think it broke the airpack and now that one problem is fixed I have to replace the airpack. Does this sound right?
I just had the genius idea to press the brake pedal while the truck is off and I can obviously tell that the air pack is not venting.
 

cattlerepairman

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Before you do the expensive stuff, do two things:

1) Check the bottom of the master cylinder reservoir for rust or crud in the small bleed hole to the rear of the larger front hole in the bottom of the reservoir. You might have to draw out some of the brake fluid with a turkey baster to see the holes well with your phone/flashlight. Slowly depress and release the brake pedal with your hand while you watch that small hole. You should see fluid squirt up momentarily from the small hole. If no fluid squirts, clear the hole with a small diameter wire or drill and by pulling up fluid with the baster. Refill clean brake fluid as needed and try the pedal again. Rinse and repeat.

The small hole is a bleed hole that allows the fluid to slowly return from the system to the master. When it is plugged, pressure remains in the booster and system, and the pedal stays high and hard.
If you see the squirt of brake fluid from the little bleed hole, do not forget to top up with fresh brake fluid before putting the cap back onto the master cylinder.

Build up air pressure and operate the brake pedal. Can you hear air exhausting from the air pack as you release the brake pedal? If not, move to 2).

2) Bleed off all system air (via air tank drains), open the hex plug at the rear of the air pack and squirt a little helping of air tool oil into the hole. If the plug won't come out, disconnect the J-shaped air pipe at the pack and squirt oil into that. This oils the "back" of the air pack where the large bore piston sits. Ideally, you would also put some oil into the incoming air line of the air pack and you may be able to get to that fitting with the air pack mounted. If you can't, follow the incoming air line back to the air tank and disconnect the line there to add oil into the line.

Build up air pressure and operate the brakes a few times. If you had to go back to the air tanks to add oil, pump the brakes a good 20-30 times, slowly and as far as the pedal will go. That should persuade the air pack to start playing nice. Hopefully it will, but it likely still will need a rebuild down the road.

If the master cylinder is working as described under 1) but you still only get the hard pedal and little braking action and cannot hear air exhaust from the air pack when releasing the brake pedal, you are looking at the air pack rebuild or replace as your next move. The control valve inside the air pack is likely the culprit and is stuck due to rust and/or debris.

If you now have air assist but get a normal or soft brake pedal, consider bleeding the wheel cylinders to make sure you do not have excessive pedal travel due to air in the hydraulic lines. Ideally, you bleed with a pressure bleeder. If you do not have one, you **can** do it conventionally with the brake pedal but it is not recommended (because you will likely have to do it three or four times over to get a "normal" pedal). Make sure to keep the master cylinder topped up while bleeding with the pedal.

Sorry for the wordy post. I tried to add all I could scrape together while sipping a coffee. Good luck!
 
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flvet352

New member
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Gainesville/Florida
Before you do the expensive stuff, do two things:

1) Check the bottom of the master cylinder reservoir for rust or crud in the small bleed hole to the rear of the larger front hole in the bottom of the reservoir. You might have to draw out some of the brake fluid with a turkey baster to see the holes well with your phone/flashlight. Slowly depress and release the brake pedal with your hand while you watch that small hole. You should see fluid squirt up momentarily from the small hole. If no fluid squirts, clear the hole with a small diameter wire or drill and by pulling up fluid with the baster. Refill clean brake fluid as needed and try the pedal again. Rinse and repeat.

The small hole is a bleed hole that allows the fluid to slowly return from the system to the master. When it is plugged, pressure remains in the booster and system, and the pedal stays high and hard.
If you see the squirt of brake fluid from the little bleed hole, do not forget to top up with fresh brake fluid before putting the cap back onto the master cylinder.

Build up air pressure and operate the brake pedal. Can you hear air exhausting from the air pack as you release the brake pedal? If not, move to 2).

2) Bleed off all system air (via air tank drains), open the hex plug at the rear of the air pack and squirt a little helping of air tool oil into the hole. If the plug won't come out, disconnect the J-shaped air pipe at the pack and squirt oil into that. This oils the "back" of the air pack where the large bore piston sits. Ideally, you would also put some oil into the incoming air line of the air pack and you may be able to get to that fitting with the air pack mounted. If you can't, follow the incoming air line back to the air tank and disconnect the line there to add oil into the line.

Build up air pressure and operate the brakes a few times. If you had to go back to the air tanks to add oil, pump the brakes a good 20-30 times, slowly and as far as the pedal will go. That should persuade the air pack to start playing nice. Hopefully it will, but it likely still will need a rebuild down the road.

If the master cylinder is working as described under 1) but you still only get the hard pedal and little braking action and cannot hear air exhaust from the air pack when releasing the brake pedal, you are looking at the air pack rebuild or replace as your next move. The control valve inside the air pack is likely the culprit and is stuck due to rust and/or debris.

If you now have air assist but get a normal or soft brake pedal, consider bleeding the wheel cylinders to make sure you do not have excessive pedal travel due to air in the hydraulic lines. Ideally, you bleed with a pressure bleeder. If you do not have one, you **can** do it conventionally with the brake pedal but it is not recommended (because you will likely have to do it three or four times over to get a "normal" pedal). Make sure to keep the master cylinder topped up while bleeding with the pedal.

Sorry for the wordy post. I tried to add all I could scrape together while sipping a coffee. Good luck!
Ok, I tried your trick with the air tool oil. It got it working for about 5 minutes, then it went back to the previous state of lock up. I bought a new air pack, was lucky enough to find the short version. I installed it last night. Now I have just a spongy pedal with no air assist. The system pumps up to 120 psi and there are absolutely no leaks now. However, when I press the pedal there are no air sounds at all. I bled the air pack using a stick to hold the pedal down until no air came out. I don't get it. Did the M/C go bad while I was working on the truck, or did I receive a faulty air pack unit?
 

cattlerepairman

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Oh no! Sorry to hear that.

"No air sounds" is definitely an airpack issue. You have been around the airpack for a while now and I do not want to come across as condescending - but the air sounds are not crazy loud and can easily be missed over an idling truck. I assume you tried it with air tanks full and engine off?

Even new airpacks have been sitting on the shelf for a few years now, probably since the 2010' at least. They have that vaseline-type assembly lube in them, so, yes, it is possible that it gets sticky. However, a new pack should not be rusty or crusty, so it should free itself with a few brake applications. You did add air tool oil when you installed the air pack, right? Both incoming lines?

I trust that you checked the master cylinder and found the fluid welling up from the bottom hole as described? As for brake bleeding, a pressure bleeder (DIY from spray bottle) is the best and you can bleed the brakes quickly and on your own.

The Deuce can be tricky to bleed with the pedal alone. As many members have experienced, it will most likely need several rounds of bleeding for the airpack and all wheel cylinders until the pedal is reliably high and firm. If you are using the pedal to bleed I am not sure it can be done (well) without a Soldier B.
 

flvet352

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Oh no! Sorry to hear that.

"No air sounds" is definitely an airpack issue. You have been around the airpack for a while now and I do not want to come across as condescending - but the air sounds are not crazy loud and can easily be missed over an idling truck. I assume you tried it with air tanks full and engine off?

Even new airpacks have been sitting on the shelf for a few years now, probably since the 2010' at least. They have that vaseline-type assembly lube in them, so, yes, it is possible that it gets sticky. However, a new pack should not be rusty or crusty, so it should free itself with a few brake applications. You did add air tool oil when you installed the air pack, right? Both incoming lines?

I trust that you checked the master cylinder and found the fluid welling up from the bottom hole as described? As for brake bleeding, a pressure bleeder (DIY from spray bottle) is the best and you can bleed the brakes quickly and on your own.

The Deuce can be tricky to bleed with the pedal alone. As many members have experienced, it will most likely need several rounds of bleeding for the airpack and all wheel cylinders until the pedal is reliably high and firm. If you are using the pedal to bleed I am not sure it can be done (well) without a Soldier B.
I squirted some air tool oil in during the install. I was having a PITA time trying to check that little hole. I just ordered a new M/C. Now that I replaced the air governor and repaired all the leaks the air system charges right up and will still have 120psi the next day. So yes I pressed the pedal and bled it with the truck off, but the airpack doesn't make a sound. I already contacted Memphis Equipment about exchanging it. You can see in one pic the rusty moisture in the airpack. In the other you can see that there is a little seepage around the M/C, but it worked fine before I took out the old airpack.20200618_060116.jpg20200618_043611.jpg
 

flvet352

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Location
Gainesville/Florida
Oh no! Sorry to hear that.

"No air sounds" is definitely an airpack issue. You have been around the airpack for a while now and I do not want to come across as condescending - but the air sounds are not crazy loud and can easily be missed over an idling truck. I assume you tried it with air tanks full and engine off?

Even new airpacks have been sitting on the shelf for a few years now, probably since the 2010' at least. They have that vaseline-type assembly lube in them, so, yes, it is possible that it gets sticky. However, a new pack should not be rusty or crusty, so it should free itself with a few brake applications. You did add air tool oil when you installed the air pack, right? Both incoming lines?

I trust that you checked the master cylinder and found the fluid welling up from the bottom hole as described? As for brake bleeding, a pressure bleeder (DIY from spray bottle) is the best and you can bleed the brakes quickly and on your own.

The Deuce can be tricky to bleed with the pedal alone. As many members have experienced, it will most likely need several rounds of bleeding for the airpack and all wheel cylinders until the pedal is reliably high and firm. If you are using the pedal to bleed I am not sure it can be done (well) without a Soldier B.
I finally got it done the other day. New M/C with the new airpack. I bled it(soldier A/soldier B method) in order from furthest to closest(again), but still had no air sounds. Had some decent pedal pressure, but no airpack. In frustration I bled it in order again and then I heard the tiniest sound from the airpack. I bled it a third time and bang, airpack is working! I don't understand why this is, I didn't even see any air coming out the second and third time I bled it. I am wondering if moisture had built up in the fluid and it wouldn't function until all new, fresh purple fluid was spurting from all six wheel cylinders. At any rate, I have the best brake pedal since I bought the truck in 2013. It puts out so much braking power, that I blew the air powered brake light switch off the truck during the test drive. Now I have to order that!20200628_195945.jpg
 

cattlerepairman

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As for the air pressure activated brake light switch, the NAPA run-of-the-mill cheapies work fine as well. You may have to make two short connector cables because the civilian switches tend to have two clamps only, but that's about it. Opening pressure is about 6 psi on the air switch.
Thread is 3/8 male NPT if memory serves.
 
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frank8003

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Just put an LED into the cab and one would always know if the switch itself is functioning with a brake pedeal press. This is just for to see if the stupid swicth is actually sending and thatswitch actually IS functioninal closed .
Do you want the information / and how to do that?\
I worked for long time on that little thing GI.
My invention but You can have it..
 

Oerthedge21

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Also, about your compressor. A ticking noise when it is engaged and building air is normal, I've never seen a deuce that doesent make that noise. Our old Mack's at work do it too. Unless your compressor is putting engine oil into your air tanks or taking way longer to build pressure than it's supposed to, there's nothing wrong with it
 

frank8003

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Get a known good, air pressure gauge that goes over 150 PSIG. Attach it with a hose to the passenger side kick board air pressure take-off valve. Run that up to where you can see it all the time. Watch that gauge operate. It wil showIMG_4299.JPG the pressure increase decrease as the regulator kicks in the compresor and kicks out. Most any new gauge would be better than the one installed on dash.
That place is air supply to fill the tires, I just tee off that for the gauge with stop valve and quick disconnect for the tire pressure fill gauge Matco.
Also see the green LED in the dash that illuminates whenever the actual brake switch functions. It does not indicate the brake lamp filiments are working, just that the switch itself is working.
 

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flvet352

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I finally got it done the other day. New M/C with the new airpack. I bled it(soldier A/soldier B method) in order from furthest to closest(again), but still had no air sounds. Had some decent pedal pressure, but no airpack. In frustration I bled it in order again and then I heard the tiniest sound from the airpack. I bled it a third time and bang, airpack is working! I don't understand why this is, I didn't even see any air coming out the second and third time I bled it. I am wondering if moisture had built up in the fluid and it wouldn't function until all new, fresh purple fluid was spurting from all six wheel cylinders. At any rate, I have the best brake pedal since I bought the truck in 2013. It puts out so much braking power, that I blew the air powered brake light switch off the truck during the test drive. Now I have to order that!View attachment 805882
Damn, I replaced the switch, everything was working great for several days. Then yesterday the pedal got squishy on me again and I thought the brand new M/C crapped out on me, but when I looked under the truck I saw the brake hose for the middle axle had blown. I mean it literally looked like flower pedals. I should have listened to the Tactical Repair channel and just replaced it all at once. Hell, after I put new hoses on, virtually my whole braking system will be new.
 
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