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How to track down air leaks?


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that the air fan control, some have a cutoff on them. I was suggesting hooking air to the air dryer input.  Did you make that happen?

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I figured that there had to be an air dryer but I’m just not seeing it. The guy I bought it from had a few other trucks that he ran, so I am not sure if the drivers were just lazy or what. I will admi

I saw a guy killed under a dump body that fell on him when I was fairly young.  Never forgot that. If you block it up, use huge, solid pieces of wood.  Don't take chances under that thing.  I don

That little red cap valve ??   That truck can ( and likely does ) have more than one. Might find one on an air tank you can see from under the truck .  And they could be on either system.  Make liked

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we got a few trucks with air start

very hard to find minor weeps

wot we do

Grab a bucket then a hand full of mums good washing powder

add water under pressure to frothup the soap stuff

then all fittings on truck throw a handfull of bubbles @ the culprix

LOL

cya

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If you post a pic of the air dryer, I should be able to tell you port to hook into.. as far as the airdryer popping off..... that depends on how much pressure the air compressor you are using can make, as long as it put's 100 or so P.S.I. into the truck your good.. 125 would be great.. Once again... The line coming off the top of the trucks air compressor, goes under the cab and changes to a rubber braided hose. It goes to the input of the dryer... jojo

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Back maybe 30 years ago i got some ear phones from radio shack that had a small mic on a cord about 5 ft long.It was good for finding air leaks behind the dash cause you could put the mic up in the dash and search for the loud hissing sound of air.I have never seen one of them after that.

glenn akers

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I have one, its around 20 years old... the name on it is "Steelman"... its still works and is sensitive. I turn the dial down when I use it..

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1 hour ago, Joey Mack said:

that the air fan control, some have a cutoff on them. I was suggesting hooking air to the air dryer input.  Did you make that happen?

I have to figure out exactly what fittings I need and track some down. Hopefully in the next few days I’ll be doing that. 

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1 hour ago, Joey Mack said:

If you post a pic of the air dryer, I should be able to tell you port to hook into.. as far as the airdryer popping off..... that depends on how much pressure the air compressor you are using can make, as long as it put's 100 or so P.S.I. into the truck your good.. 125 would be great.. Once again... The line coming off the top of the trucks air compressor, goes under the cab and changes to a rubber braided hose. It goes to the input of the dryer... jojo

I have to look for the air dryer, I don’t know where it’s located. 

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its bolted to the frame, mostly on the right side. Its round, it may be 8" across and near a foot tall. (AD-9). or it could be half that size with a screw on filter, like a big oil filter.. Look behind the right tank on the frame.... jojo

Edited by Joey Mack
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Posted (edited)
16 minutes ago, Joey Mack said:

its bolted to the frame, mostly on the right side. Its round, it may be 8" across and near a foot tall. (AD-9). or it could be half that size with a screw on filter, like a big oil filter.... jojo

I just went out and looked and I’m not seeing it. It’s also getting dark out so that may be a factor. I’m sure it’s right in front of my fave and I was looking right at it

Edited by Dmurph2016
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3 hours ago, Dmurph2016 said:

So I only had a few min today to use the soap and water before the weather turned to rain, but here’s what I got done. 
stsrted the truck and let it air up until the governor shutoff. Shut the truck off. Could hear some air leaking from the front of the truck, o opened the hood and started spraying airlines. Not exactly sure what this thing is or does but it was bubbling at the red part. Secondly I confirmed that when I flip the switch to drop the lift axle, the green needle dropped. So it seems that there’s a leak somewhere in that system and when it loses pressure, the axle drops. It’s a start. Hopefully when the rain stops o can lift the bed up and start checking under there. As well as the brake cans as I have a feeling that could also be a culprit 

C88D9C0B-F02E-4E13-855E-664E545D178E.jpeg

That's a cutoff for if the air drops too low. It's purpose is to stop air from going to something less important than brakes. ( like suspension ) they're regulated and colored for how many pounds they allow.  With the truck shut off ? The gauge should drop as the lift axle is put down ( air's going to filling the bags )  there's reservoir ports on the govener that'd probably be really easy to charge the truck with shop air

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25 minutes ago, Mark T said:

That's a cutoff for if the air drops too low. It's purpose is to stop air from going to something less important than brakes. ( like suspension ) they're regulated and colored for how many pounds they allow.  With the truck shut off ? The gauge should drop as the lift axle is put down ( air's going to filling the bags )  there's reservoir ports on the govener that'd probably be really easy to charge the truck with shop air

There’s a tire fill port on the primary air tank, if I can fill it from there?

So I’ll need to replace the cutoff?

Yes, the gauge is going to drop with the truck off and dropping the axle. But after sitting for 2-3 hours the axle is down as it’s lost too much air, so there has to be something leaking pretty good somewhere in that system. The other system loses air but not at that rate. Although with the truck off and press the pedal you can hear air from the back of the truck. So I’m making progress. 

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1 hour ago, Joey Mack said:

it may be one of these..

1.jpg

2.jpg

th.jpg

I didn’t see anything like that.. unless it’s under the dump bed. I didn’t see it on the frame. Unless it’s mounted on the engine? There’s no room on the sides as it’s fuel tanks, battery boxes and air tanks on both sides 

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The CLs I had, the air dryer was right in the area about where the back of the transmission is. Mounted inside the frame. ( this doesn't mean your's is )  Yes the tire valve you mentioned, you can put shop air in there. The cutoff/ regulator ( thing with red cap ) if it's leaking, it's shot.  The brake air leak is likely a diaphragm in a service chamber

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Posted (edited)
12 hours ago, Mark T said:

The CLs I had, the air dryer was right in the area about where the back of the transmission is. Mounted inside the frame. ( this doesn't mean your's is )  Yes the tire valve you mentioned, you can put shop air in there. The cutoff/ regulator ( thing with red cap ) if it's leaking, it's shot.  The brake air leak is likely a diaphragm in a service chamber

I’ll have to lift the body up, I’m sure it’s mounted under there. 
If I hook shop air up to the primary tank, will it also fill the secondary? And when it hits 120 or whatever the cutoff is it’ll release? I don’t want to blow anything up. Or should I look for the dryer and then connect into that instead of the tAnk?
For the regulator thing with red cap, is that a dealer only part? I believe it’s a pressure protection valve?
I’m going to assume it’s the diaphragms that are leaking. But going to start with the smaller things first. 

Edited by Dmurph2016
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I'd get the red thing from your dealer by the VIN of the truck . I've seen them at parts places, but not sure the port sizes will be direct replacement on your's.  Charging the truck from shop air ?  not much chance you'll hurt anything. Joey's idea about going in the compressor discharge is a good place, and when it hits @ 120 you'll hear your air dryer go off. ( if you're worried about too much )  Likely charging in the primary tank won't hurt either.  If this truck has leaks from valves you may want to consider finding that air dryer and replacing the desiccant at least.  Only reason I suggested the governor  was it's marked and probably easier to get at....and air will go in the truck much slower through a tire valve in one of those little ports.

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810-032221_800AT_540x540.jpg[img]C88D9C0B-F02E-4E13-855E-664E545D178E.jpeg[/img]

Th@ red button doodadd isa  pressure protection valve

The velvac valve available with 85,70, 67psi or black button of 45psi

 

could B setup to air up the air ride cab when the psi is reached

BIDS2BC

cya

 

Edited by Swishy
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11 minutes ago, Mark T said:

I'd get the red thing from your dealer by the VIN of the truck . I've seen them at parts places, but not sure the port sizes will be direct replacement on your's.  Charging the truck from shop air ?  not much chance you'll hurt anything. Joey's idea about going in the compressor discharge is a good place, and when it hits @ 120 you'll hear your air dryer go off. ( if you're worried about too much )  Likely charging in the primary tank won't hurt either.  If this truck has leaks from valves you may want to consider finding that air dryer and replacing the desiccant at least.  Only reason I suggested the governor  was it's marked and probably easier to get at....and air will go in the truck much slower through a tire valve in one of those little ports.

I will have to call the dealer tomorrow and find out about the part. 
I was thinking about it earlier today, its going to take forever with the tire valve, so I think going in elsewhere May be faster. I need to find the filter and change that. 
Are the fittings something that I can get locally or will they need to be ordered? 

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I just replaced one on an ASET, it supplied air to  the VGT system. I also replaced the bad air filter on that system. the air leak was fixed and the VGT, worked again.. This may not apply, but......  jojo

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I looked and I still for the life of me cannot find the air dryer. I’m not sure what the issue is with that. I called local Mack dealer and they have a pressure relief valve in stock so I will pick that up. I noticed this today, so looks like I’ll also be needing to replace at least 1 front brake can unless the hole is there for performance 😂 so add that to the list.

072930DF-0190-421C-96FF-56E26D75CD3E.jpeg

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Maybe it never had a air dryer, I  have never seen a air dryer in my life so although they are common in the US Im guessing that they arent fitted to every truck

 

Or theres also most likely is, I just dont know my ass from elbow 

 

Paul

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its possible that there isn't a dryer. I would expect this year model to have one, It could have been removed by the previous owner, who knows.. judging by the brake chamber picture, i'm guessing "Pre-trip" was not part of the previous owners day. and maintainance,,, well????.. All of us will help him get his truck fixed up. :)

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34 minutes ago, Joey Mack said:

its possible that there isn't a dryer. I would expect this year model to have one, It could have been removed by the previous owner, who knows.. judging by the brake chamber picture, i'm guessing "Pre-trip" was not part of the previous owners day. and maintainance,,, well????.. All of us will help him get his truck fixed up. :)

I figured that there had to be an air dryer but I’m just not seeing it. The guy I bought it from had a few other trucks that he ran, so I am not sure if the drivers were just lazy or what. I will admit I’m new and clueless so I may have overlooked some things when I looking at it, but hey nothing I can do but fix and move on. Chalk it up to life lesson.

attached is a photo of the truck.

 

FC1821B0-2C70-4862-9395-090DE7D12112.jpeg

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