The Nitro Posted June 26, 2022 Author Share Posted June 26, 2022 Thanks for the help mate. I will buy 4 new cans and see if that fixes it. I will keep trying to get it to leak again today but seems the cans are the best place to look from all advice here so far. thanks guys 1 Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/3/#findComment-501294 Share on other sites More sharing options...
Mark T Posted June 26, 2022 Share Posted June 26, 2022 That chamber in the box ? It's not caged. You can see the cage bolt stowed away on it in the picture. That means the pushrod is sticking out. No offence, but if you don't understand that maybe working on the brakes isn't the greatest idea (again, NO OFFENCE) Someone likely put a boggie from another truck under there and Lord knows how it's plumbed or what else is going on there. Might be time to get some hands on help that can assess the situation , and make the repairs it needs. Might turn out to be the cheapest route in the long run. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/3/#findComment-501295 Share on other sites More sharing options...
Onyx610 Posted June 26, 2022 Share Posted June 26, 2022 (edited) Not only should it not go past 90 degrees, they should be setup to be at 90 degrees with brakes applied. Maximum brake power at 90 degrees. Your brakes are not setup correctly. Edited June 26, 2022 by Onyx610 Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/3/#findComment-501296 Share on other sites More sharing options...
The Nitro Posted June 26, 2022 Author Share Posted June 26, 2022 The brakes in box are uncaged. Ahhhh I see. what Mark T just said just clicked for me. In other words the brakes are fully on in the boxed cans. If I were to remove my old brake can I am now suspecting its rod will also stick out more than it is now on truck its just that the brake adjustment is preventing it. yes your right I’m new to trucks and havn’t understood how it all works. But learning as I go with this forum help. Its making sense now. I was forgetting the rod in my can on truck is so short as the caliper is stopping it going to its full extended range like the new one in box is showing. I’m now thinking I may have to leave brake hoses connected with brakes released to remove can or else insert the caging bolt to get the pressure off the eye to remove pin. I think I’m learning something guys. Haha. Appreciating the help for sure. Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/3/#findComment-501301 Share on other sites More sharing options...
The Nitro Posted June 26, 2022 Author Share Posted June 26, 2022 (edited) I was thinking the 90 degrees would also be maximum leverage and not sure why the rego guy has tightened the brakes that much. I also felt he adjusted brakes a bit short as I had adjusted them all to 90 degrees myself prior to taking truck in for rego inspection but didnt question him as he is the guy passing it for rego/ mechanic and I’m just a back yarder learning best i can as I go along. Edited June 26, 2022 by The Nitro Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/3/#findComment-501302 Share on other sites More sharing options...
The Nitro Posted June 26, 2022 Author Share Posted June 26, 2022 I might try taking a can off truck and see how it looks once its at its fully extended length like the new one is and it may work afterall. Mechanics are on $180 an hr here so If I can figure this stuff out via this forum and my pictures I post it will surely help me out. Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/3/#findComment-501303 Share on other sites More sharing options...
theakerstwo Posted June 26, 2022 Share Posted June 26, 2022 And i can remember when in 1968 freight liner here was 11.00 per hr.When i started to work on trucks it was in early 1965 and mack was 5.00 per hr and in less than a year they went to 5.50 per hr. 1 Quote glenn akers Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/3/#findComment-501304 Share on other sites More sharing options...
Onyx610 Posted June 26, 2022 Share Posted June 26, 2022 Do you have to have your brakes adjusted? Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/3/#findComment-501305 Share on other sites More sharing options...
Joey Mack Posted June 26, 2022 Share Posted June 26, 2022 $166.00/hr. here in Salisbury N.C. at the itty bitty MACK dealer here.. Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/3/#findComment-501306 Share on other sites More sharing options...
The Nitro Posted June 26, 2022 Author Share Posted June 26, 2022 I’m now starting to think I need to try remove all 4 cans and check the stickout length of them to eye from the mounting face uncaged and see if the 2 new cans i bought allow enough threads to end up with the same length. If so... i just wind the eye down on new cans to same length as old ones. Chop excess thread off and lock nut up and re install. Is this right? Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/3/#findComment-501307 Share on other sites More sharing options...
The Nitro Posted June 26, 2022 Author Share Posted June 26, 2022 I can use the allen head bolt in the caliper to set the brakes to 90 degrees after new cans are on yep. Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/3/#findComment-501308 Share on other sites More sharing options...
The Nitro Posted June 26, 2022 Author Share Posted June 26, 2022 Just watched video that was posted about how to set pushrod length. Made sense to me. Thanks Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/3/#findComment-501309 Share on other sites More sharing options...
Onyx610 Posted June 26, 2022 Share Posted June 26, 2022 I’m going to say your truck is not setup correctly. The clevis on your chambers are hitting the mounting bracket and preventing the brakes from fully releasing and probably from auto adjusting. Setting up a chamber to the correct length isn’t always as easy as it seems. Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/3/#findComment-501310 Share on other sites More sharing options...
MACKS Posted June 26, 2022 Share Posted June 26, 2022 The info and video I posted is for drum brakes,don’t know anything about disk brakes so I’m out,good luck.. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/3/#findComment-501311 Share on other sites More sharing options...
Mark T Posted June 26, 2022 Share Posted June 26, 2022 The term "caging" is referring to the parking brake part of the air chamber (spring brake) if you try removing the air chamber on the truck with the parking brake on and the spring not caged the chamber is going to be spring loaded and as you loosen the mounting nuts the chamber is going to be trying to extend the rod . !!! This is a good way to get hurt !!! Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/3/#findComment-501313 Share on other sites More sharing options...
mechohaulic Posted June 26, 2022 Share Posted June 26, 2022 1 hour ago, The Nitro said: I’m now starting to think I need to try remove all 4 cans and check the stickout length of them to eye from the mounting face uncaged and see if the 2 new cans i bought allow enough threads to end up with the same length. If so... i just wind the eye down on new cans to same length as old ones. Chop excess thread off and lock nut up and re install. Is this right? MAKE SURE THERE ARE WHEEL CHOCKS BEHIND AND IN FRONT OF ALL WHEELS BEFORE REMOVING CANS. take off 4 cans nothing is holding truck in place i DON'T trust in gear. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/3/#findComment-501317 Share on other sites More sharing options...
The Nitro Posted June 26, 2022 Author Share Posted June 26, 2022 Ok guys, made some progress. Yes the truck wheels are chokked up nicely. So I just started truck again and its leaking bigtime again. It wont even build up maximum air pressure because of that leaking flap on bottom of valve i showed. So I removed all 4 service brake lines off cans and none of them have air leaking out from cans. Hmmm but the leak is still roaring out from that valve. it appears its not the cans inner seal at fault. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/3/#findComment-501319 Share on other sites More sharing options...
The Nitro Posted June 26, 2022 Author Share Posted June 26, 2022 This is the valve that feeds the service brakes on both rear axles via the black hoses and has the air leaking out bottom. The air is leaking to the black service lines rather than leaking back from the service brake lines. I removed the yellow hose and air is coming out of it and going into the valve and leaking directly out bottom flap. i followed yellow hose and it comes from this valve shown below on other side of frame that feeds the park brakes on cans. I tried hitting this valve with hammer and it didnt seem to change the big leak still coming from service brake valve. i followed orange lines on this park brake valve towards cab and find this valve shown below: When I hit this valve with hammer the leak changes a lot. Im not sure what this valve does but its looking like it might be the problem. Unless its even farther upstream from this one I have no idea but thinking I might try buying a new one of these and see.? Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/3/#findComment-501320 Share on other sites More sharing options...
mrsmackpaul Posted June 26, 2022 Share Posted June 26, 2022 3 hours ago, Onyx610 said: Not only should it not go past 90 degrees, they should be setup to be at 90 degrees with brakes applied. Maximum brake power at 90 degrees. Your brakes are not setup correctly. That isnt correct, they should not be set like this as once any wear is apparent they will be past 90 degrees Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/3/#findComment-501321 Share on other sites More sharing options...
The Nitro Posted June 26, 2022 Author Share Posted June 26, 2022 Just started truck again and the leak is stopped again. No amount of hitting valves with hammer can invoke it. Guess I will drain tanks and keep trying to get it to leak again. I’ve saved probably $600 in labour soo far trying to find it so thats good hahaha. Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/3/#findComment-501322 Share on other sites More sharing options...
Onyx610 Posted June 26, 2022 Share Posted June 26, 2022 12 hours ago, mrsmackpaul said: That isnt correct, they should not be set like this as once any wear is apparent they will be past 90 degrees Not if your “automatic slack adjusters” are working correctly…. Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/3/#findComment-501349 Share on other sites More sharing options...
mowerman Posted June 26, 2022 Share Posted June 26, 2022 Yes those pots are evil I don’t recommend you take them apart I have done it but these days I get nervous just walking by them …bob Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/3/#findComment-501364 Share on other sites More sharing options...
Mark T Posted June 26, 2022 Share Posted June 26, 2022 Just curious , did some genius just hack into that for the trailer brakes ? It's pretty tough to try and determine what might have actually been done to that truck. Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/3/#findComment-501370 Share on other sites More sharing options...
Swishy Posted June 26, 2022 Share Posted June 26, 2022 When the air is coming out big time grab a hose and wiggle to see if the air noise differs me guessing a hose @ the valve fitting is broken do each hose them plastic hoses do crack and break right @ the end where its squashed in to the end valve cya Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/3/#findComment-501378 Share on other sites More sharing options...
The Nitro Posted June 26, 2022 Author Share Posted June 26, 2022 There is a red button on dash in cab to push in to release trailer brakes next to the yellow one and it looks to be run through some sort of brake away safety air valve at rear of truck and the connection of air lines to trailer is via a double port flat face coupler where you pull a spring lever and it pinches them together. I will have a look at trailer brake hoses on truck side and try figure out how that works or how thd air gets there. the service brake valve is the one that leaks out bottom flap. It takes signal by foot brake via small green hose on top and sends air to both black hoses to cans service ports. The yellow hose is t into one of service brake ports at the valve and looks like its supposed to get pressured up the same as service brakes and heads over to park brake valve. (Not sure why) but while the leak is present the air is coming back from yellow hose park brake valve. I think its not supposed to do that. So im guessing either the park brake valve is leaking or the other one with orange hose in front of it. The leak doesnt sound like plain leak like if you had a hole in a tyre, it sounds more like a duck quacking over and over Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/3/#findComment-501384 Share on other sites More sharing options...
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