The Nitro Posted June 6, 2022 Share Posted June 6, 2022 Hi guys, I have a 2004 mack vision tipper thats leaking air out of this air brake part with air brakes released. if i put my fingers over the flap on bottom where air leaks out to try stop leak then I can see all 4 rear brake come on. I replaced the valve with a new one and it still does it? it sits on chassis just in front of the dual axles. Something else might be wrong but not sure where to look. any ideas? thanks. Quote Link to comment Share on other sites More sharing options...
Popular Post theakerstwo Posted June 6, 2022 Popular Post Share Posted June 6, 2022 You have a spring chamber leaking thru its self to the service side and exhausting out there.Disconnet each service line to the brakes and release the parking brakes and you will find one leaking out of the chamber. 3 Quote glenn akers Link to comment Share on other sites More sharing options...
mrsmackpaul Posted June 6, 2022 Share Posted June 6, 2022 (edited) As already said a maxi can is leaking, for the price of them I would just change all 4 Thats me just spending with gay abandone 😂😂 Paul Edited June 6, 2022 by mrsmackpaul 1 Quote Link to comment Share on other sites More sharing options...
Swishy Posted June 6, 2022 Share Posted June 6, 2022 As Theackers2 sez Between the 2 air chambers Parking Brake/ Service brakes there is a 'O' ring or 2 th@ when air leaks past the 'O' ring it can apply the service brake depending on how servere the leak is If you no what U are doing you can replace the 'O' ring/s if it is a demountable lock ring on the spring brake but make sure u're life insurance is fully paid up before atempting to dismantle Cya 1 Quote Link to comment Share on other sites More sharing options...
The Nitro Posted June 6, 2022 Author Share Posted June 6, 2022 Ah, ok thanks guys I will have a look at the brakes and see If I can find which one it is. I’m not confident to disassemble a chamber safetly so might just replace the whole thing. I seem to be getting to know Andrew (mack parts dealer) pretty well now hahaha. Thanks again for the help. Quote Link to comment Share on other sites More sharing options...
MACKS Posted June 6, 2022 Share Posted June 6, 2022 If you can’t hear it spray a little soapy water on it,forget about taking it apart there cheap enough to just replace and grab an extra one while your there.. 2 Quote Link to comment Share on other sites More sharing options...
Popular Post Joey Mack Posted June 6, 2022 Popular Post Share Posted June 6, 2022 no... you dont need to take a brake chamber apart..... just do what Glenn said, or take a long nose vise grip and clamp it to one brake chamber at a time, on the park brake side... the rearward hose... then release the brakes... wheel chocks in place please!!! do this for each chamber until you hear the leak stop... hell, if you have 4 of these vise grip's, clamp all 4 lines, and push the yellow button in, (air pressure needs to be up, leave it running) then remove one vice grip at a time til you hear the leak. that will be the bad chamber.. no need to cut through the rubber air hoses with a death grip, just snug.. But Glenn told you a good way to get the same results... jojo 3 1 Quote Link to comment Share on other sites More sharing options...
Swishy Posted June 9, 2022 Share Posted June 9, 2022 TheNitro Gudday m8 sum of us are looking for closure on this problem What did you find & how did you fix it cya 1 Quote Link to comment Share on other sites More sharing options...
theakerstwo Posted June 9, 2022 Share Posted June 9, 2022 I hope he didnt try taking one of the chambers apart because he may not be around anymore. 2 Quote glenn akers Link to comment Share on other sites More sharing options...
doubleclutchinweasel Posted June 10, 2022 Share Posted June 10, 2022 I just saw this thread. Great advice from everyone, as usual. And, an easy one to find/fix. Like Glenn said, I hope he didn't try to disassemble that hand grenade! 2 Quote "Eagles may soar, but weasels don't get sucked into jet engines." Link to comment Share on other sites More sharing options...
Freightrain Posted June 17, 2022 Share Posted June 17, 2022 Just saw this also. My relay valve blew the diaphram and dumped my air tank. Luckily I was in the driveway! Hopped in pickup and ran to parts store and got new valve. Only lasted 20 yrs. Lol. Quote Larry 1959 B61 Liv'n Large...................... Charter member of the "MACK PACK" Link to comment Share on other sites More sharing options...
Popular Post mrgumby Posted June 17, 2022 Popular Post Share Posted June 17, 2022 20 years you say. Well we know it wasn’t made in china. 1 2 Quote Link to comment Share on other sites More sharing options...
The Nitro Posted June 25, 2022 Author Share Posted June 25, 2022 (edited) Hi guys, just got time today to investigate this air leak problem and I have bought 2 new 20/24 spring brakes. I have not put the new ones on yet. So, i start truck and get air up, release the brakes and I get the air leak out the bottom flap valve. I turn truck off and almost Immediately the air leak stops. If I turn key on again the leak is not leaking. If I restart truck The leak starts again??? I have not disconnected any lines yet to see which spring brake might be faulty but this leak stopping when I turn truck off has me puzzled. How would the spring brakes know the truck is running or not, an oring in spring brake can’t fix itself with truck turned off and then damage itself once trucks re started so I’m trying to understand what happens to this leak stopping when engine gets turned off? wouldnt a leaking oring in spring brake keep on leaking whilever pressure is on the line? is there some valve that disconnects spring brake air when motors off? was hoping to have motor off so i could hear which spring brake might be leaking but it stops leaking soon as i turn truck off lol Edited June 25, 2022 by The Nitro Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted June 25, 2022 Share Posted June 25, 2022 the brake valve is bad... it gets constant air pressure to it as long as there is air to be delivered.. the spring brakes dont have air pressure in the chamber until you push the brake release valve in... on the brake valve in the frame, there should be an air supply line, and a signal line ( brake release valve line) and 2 or 4 lines off the bottom to the rear chambers on the maxicans.. more pictures are always a good thing,.. jojo Quote Link to comment Share on other sites More sharing options...
The Nitro Posted June 25, 2022 Author Share Posted June 25, 2022 Ok will get some pics. Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted June 25, 2022 Share Posted June 25, 2022 just curious,,,, why such small maxi's? why not 30/30's? Quote Link to comment Share on other sites More sharing options...
The Nitro Posted June 25, 2022 Author Share Posted June 25, 2022 I dont know why? The truck according to mack dealers via vin number has spring suspension and drum brakes but truck has meritor air bag diffs and disc brakes all round. Also according to registration papers the truck has been upgraded from 70 tonne gcm to 80 something tonne gcm. Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted June 25, 2022 Share Posted June 25, 2022 ok,,, disc brakes.. I guess thats why, no room for big chambers.. I didnt know the year/model of the truck... jojo Quote Link to comment Share on other sites More sharing options...
The Nitro Posted June 25, 2022 Author Share Posted June 25, 2022 This valve is the new one which is leaking just the same as old one I took off. It sits on left (standing behind truck) hand side of chassis just in front of rear diffs. The black hose on right leads to front dual diff brake boostes at the ports closest to the rod that comes out and the black hose on left leads to rear diff brake boosters at the port closest to the rod as well Quote Link to comment Share on other sites More sharing options...
The Nitro Posted June 25, 2022 Author Share Posted June 25, 2022 This valve is on other side of chassis and the black hoses lead to the front and rear dual diffs brake boosters ports farthest from the rods Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted June 25, 2022 Share Posted June 25, 2022 the second valve should be the service valve... the one that applies the brakes when you step on the pedal.. the first pic is the park brake valve... Did you do what Glenn asked, and remove a service line from each brake chamber until the leak stopped? you may have a backfeed through the maxi.. Quote Link to comment Share on other sites More sharing options...
The Nitro Posted June 25, 2022 Author Share Posted June 25, 2022 Then these 2 valves are also on right side of truck chassis (standing behind truck) closer to cab than the last valve above i showed but I dont know what they do. the valve that leaks air out bottom is the new one that sends air to all brake booster ports closest to rods but stops soon as trucks turned off even though all air tanks still full Quote Link to comment Share on other sites More sharing options...
The Nitro Posted June 25, 2022 Author Share Posted June 25, 2022 Its s 2004 mack vision tip truck with doff locks and cross locks and full air brakes Quote Link to comment Share on other sites More sharing options...
The Nitro Posted June 25, 2022 Author Share Posted June 25, 2022 Ea7 470 hp motor and 18 speed roadranger crash box with a very stiff clutch pedal lol Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted June 25, 2022 Share Posted June 25, 2022 oh hell, the small one is likely a pressure protection valve, and the other one should be the anti compounding valve. My guess is you have a bad maxi, if the plumbing is correct.. Quote Link to comment Share on other sites More sharing options...
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