How to track down air leaks?

[Joey Mack]

That's a great truck... No sweat... many of us here can help you... Can you raise the body and snap some pic of the frame just behind the cab? stand back some to catch as much as possible.. then post them..  I will come back and look..  Jojo .....your in the right place here..

[Mark T]

1 hour ago, Dmurph2016 said:

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.

 

That looks like an old Capone truck.

[Dmurph2016]

38 minutes ago, Mark T said:

That looks like an old Capone truck.

Could be? Not sure what company that is. 

[Mark T]

They used to run around south east pa and nj.    They had trucks similar to yours 

[Dmurph2016]

On 4/2/2021 at 8:26 PM, Mark T said:

They used to run around south east pa and nj.    They had trucks similar to yours 

It very well could be, the truck came from that area.

[Mark T]

The ones I'm thinking of were kinda nice. A few used ones ended up around where I'm from. They were nice used trucks,and there's still a couple around

[Dmurph2016]

So little update, today I was able to install the new pressure valve. That I purchased yesterday. Take it off try to put the end one one, and the threads the wrong side. 40 min back to the dealer got the right one, put it on and it’s still leaking. ( I didn’t snug it up enough) so I gotta take the fittings off and do it again tomorow. While checking I put the parking brakes off and noticed this was hissing air. Only did it 2ce though so not sure if it’s just coincidental or not. See second video. 
then with the parking brake off, I was pumping the brakes is both needles supposed to drop? The green needle is the one that has the lift axle on it and has been dropping within a few hours of sitting. (First video ) 

 

Edited April 6, 2021 by Dmurph2016

[Dmurph2016]

[Mark T]

I'm think'n that no matter what's leak'n on your truck ??  do yourself a favor and replace all four air chambers on the back of it.  I'd suggest 4 MGMs . They cost a lot, and if you don't know how to change them you'd be best to let someone who does. You really can't go wrong with new chambers....unless you don't know how to change them. Between putting air lines back on and cutting the push rod to the correct length, let alone it's not impossible to hurt yourself with the parking brake they're nothing to play with unless you know.  I think some of your leaks are from the air chambers . those gauges dropping with the application look about normal ???  

[MackTech]

On 3/31/2021 at 4:42 PM, 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 

The green needle is for primary air. The red is for secondary.  The lift axle should be operating off of a solenoid.  When I'm the up position the solenoid will provide air to the lift bags and when in the ride position the air will go to the ride bags.

Now if you have a loss of air when I'm the up position, you'll want to check the ride bags. Then check the solenoid. Check the supply line for the solenoid which is very likely coming from a "red hat" pressure protection valve like you have in your picture.  I am pretty sure the CL pooping is different than the current generation trucks as the newer trucks have an air\elec solenoid pack near the right side front of bogey cross-member.  

Not sure where your solenoid is as the lift axle is very likely an add after the truck was built.

If the lift axle was put on in the mod center at the factory, I don't remember how they did them on CLs.

 

Maybe this might help.

[Dmurph2016]

On 4/6/2021 at 6:02 PM, Mark T said:

I'm think'n that no matter what's leak'n on your truck ??  do yourself a favor and replace all four air chambers on the back of it.  I'd suggest 4 MGMs . They cost a lot, and if you don't know how to change them you'd be best to let someone who does. You really can't go wrong with new chambers....unless you don't know how to change them. Between putting air lines back on and cutting the push rod to the correct length, let alone it's not impossible to hurt yourself with the parking brake they're nothing to play with unless you know.  I think some of your leaks are from the air chambers . those gauges dropping with the application look about normal ???  

I’m going to find a shop and have them change them. I was thinking of just having them replace the rubber diaphragm, but it may make more sense to just replace the whole cans for the peace of mind. I have a feeling that could be part of the air leak I’ve got going on

[Dmurph2016]

16 hours ago, MackTech said:

The green needle is for primary air. The red is for secondary.  The lift axle should be operating off of a solenoid.  When I'm the up position the solenoid will provide air to the lift bags and when in the ride position the air will go to the ride bags.

Now if you have a loss of air when I'm the up position, you'll want to check the ride bags. Then check the solenoid. Check the supply line for the solenoid which is very likely coming from a "red hat" pressure protection valve like you have in your picture.  I am pretty sure the CL pooping is different than the current generation trucks as the newer trucks have an air\elec solenoid pack near the right side front of bogey cross-member.  

Not sure where your solenoid is as the lift axle is very likely an add after the truck was built.

If the lift axle was put on in the mod center at the factory, I don't remember how they did them on CLs.

 

Maybe this might help.

If green is primary then there is a major leak going on. I figured the red would be primary, reason being after 2-3 hours of sitting the red Harley moved while the green dropped down to almost below 60 or so. ( when you flip the switch for the lift axle green needle dropps, and when in the up position as the air drops to 60 the axle will drop down)
I am assuming the lift axle was put on when the body was put on. I’ll have to look for the solenoid, I’m guessing it’s under the bed 

 

[Joey Mack]

Its always good to keep the truck in good repair, especially the D.O.T. items,(safety)..  However... when the truck is parked, and the brakes are "Set"... There is NO air going to the brake chambers... The air is leaking in other places...  when sitting.. My guess is this truck has air switches for the tag axle and body controls...  If there is an electric selenoid in-line, check those closely. jojo

[Joey Mack]

some one plumbed the axle to the primary, it needs to be on the secondary. The main supply out of the secondary tank needs a "Pressure Protection Valve" installed at the tank. so that if a failure occurs on the tag axle it wont drain most of the air needed to "Stop"!

[Mark T]

Often brake chambers can blead back from side to side especially those cheap gold ones. Might be what's causing the inversion valve leak ?  He said he had a leak upon brake application in the rear and the front is actually rotted to the point of having a hole.  The lift axle ?  Hard to say what arrangement is on that. Could be electric over air or all air ....or maybe even a make that doesn't even use air to lift ( like Neway)   need some pictures of this unit 

[Dmurph2016]

10 minutes ago, Joey Mack said:

some one plumbed the axle to the primary, it needs to be on the secondary. The main supply out of the secondary tank needs a "Pressure Protection Valve" installed at the tank. so that if a failure occurs on the tag axle it wont drain most of the air needed to "Stop"!

Isn’t that the valve that I just replaced? Not on the tank though. I’m going to assume the way it is setup is the way the body manufacture set it up, not sure why you’d go messing with what’s on what system?

[Joey Mack]

Good call Mark!   and pics would help a bunch.. The MGM chambers you suggested are top notch..  jojo

[Mark T]

3 minutes ago, Dmurph2016 said:

Isn’t that the valve that I just replaced? Not on the tank though. I’m going to assume the way it is setup is the way the body manufacture set it up, not sure why you’d go messing with what’s on what system?

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 that particular brand back in that era

[MackTech]

3 minutes ago, Dmurph2016 said:

Isn’t that the valve that I just replaced? Not on the tank though. I’m going to assume the way it is setup is the way the body manufacture set it up, not sure why you’d go messing with what’s on what system?

The valve in the pic you posted is one of the old style pressure protection valves.  It will close when the pressure gets to low to protect against too much air loss which could seriously affect controlled braking.  Once you lose too much air your yellow button will pop out and your spring brakes will lock up.

[Joey Mack]

I dont know how many different ways there are to plumb the tag axle, but I have never taken my air supply from the firewall... I always go to the secondary tank and first install a 65PSI protection valve then from it, supply the tag axle system. 

[MackTech]

18 minutes ago, Joey Mack said:

some one plumbed the axle to the primary, it needs to be on the secondary. The main supply out of the secondary tank needs a "Pressure Protection Valve" installed at the tank. so that if a failure occurs on the tag axle it wont drain most of the air needed to "Stop"!

Prior to Volvo dictating air piping Mack piped lift axles to the primary tank with a pressure protection valve.  I remembered when they changed it at the plant.

[Joey Mack]

Isnt that used on this chassis  for the VGT air supply? I need to look back at the year of this truck now.. i forgot. 

[Mark T]

1 minute ago, Joey Mack said:

Isnt that used on this chassis  for the VGT air supply? I need to look back at the year of this truck now.. i forgot. 

Mack liked that valve, they used it on several things that weren't brakes and used air

[Dmurph2016]

I just snapped a few pics, not sure if they help, but if you need any specific pics let me know and I’ll see what I can do. 

[Dmurph2016]