The Nitro Posted June 26, 2022 Author Share Posted June 26, 2022 The duck quacking type sound is almost telling me there is some sort of spring involved in the fault Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/4/#findComment-501385 Share on other sites More sharing options...
The Nitro Posted June 26, 2022 Author Share Posted June 26, 2022 I might need to find an air diagram somewhere to try understand how the entire brake system works and see if that yellow hose is supposed to have air coming out of it from park brake valve to service brake can lines or not. I would of thought the air is meant to go up yellow line to park brake valve instead to tell park brake valve that service brakes are on. I have no clue really but the yellow hose is where the leak is coming from. It seems to just come into service brake valve and dump out the flap at bottom. Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/4/#findComment-501386 Share on other sites More sharing options...
The Nitro Posted June 26, 2022 Author Share Posted June 26, 2022 Air pressure governor valve is new and i backed it off slightly from where it was set by factory. Air gauge reads 9.5 in dash. I dont know if thats too high still and its causing problems but truck was running fine and the leak just appeared randomly Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/4/#findComment-501387 Share on other sites More sharing options...
The Nitro Posted June 26, 2022 Author Share Posted June 26, 2022 Truck has only been back on rd for a few months after a couple years sitting. It had all sorts of air leaks when i bought it. One in axle diff lock, governor valve, air hoses, service brake valve, air seat hose fittings, a buggered check valve at wet tank, the treadle valve, etc. slowly getting it all fixed as things pop up. We will get there, but this one is taking a bit of time to track down. Appreciating the help for sure. Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/4/#findComment-501388 Share on other sites More sharing options...
Joey Mack Posted June 26, 2022 Share Posted June 26, 2022 OK.. I said that I was out.... But really sir,, you need to slow down.... this is not as big'a deal as you have been posting.. It's not "Rocket Surgery"... Just for kicks,, replace all the cans and the valves, and then you will find out that there was a crappy dash valve... anytime air is delivered based on the key switch means its electric over air... however, you need to have a stored supply of air over 90 PSI... so now???? does the truck leak down over night or in an hour?? or what??.... I feel like you have a small amount of knowledge, and folks are taking advantage of you..... Please keep trying to fix this yourself.. You really need to pay attention to what Glenn Akers said, and a few others.. jojo 1 Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/4/#findComment-501389 Share on other sites More sharing options...
The Nitro Posted June 26, 2022 Author Share Posted June 26, 2022 its my first truck mate, I didnt even know what a treadle valve or any valve at all on the truck was for untill a few months ago when I bought the truck. I’m a truck green horn. But I do like the challenge of learning how things work and trying to fix them. I’d be entirely lost without this website as its here where im getting help to fix all the problems I’ve found so far. The truck leaks down overnight while park brakes are on. A little comes out from cab air bag valve and a little from dryer valve and a little from rear airbag height valve. this leaking service brake valve is intermittent. Sometimes it leaks for 20 seconds then stops then sometimes it leaks continuous and the leak is significant that the compressor cant deliver more than 8 on dash guage where it is usually at 9.5 while its not leaking. I bought 2 new cans hoping it might be the inner seal on a can like was suggested. Removing all 4 can hoses (service brake side) while valve was leaking revealed the cans are not the problem as the air is coming from yellow hose and not cans. When its not leaking theres no air coming out yellow hose from park beake valve. So Turned my attention and hammer to that park brake valve and the one upstream from it. I have no understanding of how the circuits works and even less of the dash pull push buttons for brakes. But the problem started after I bought the trailer a month ago or whenever it was and started hooking trailer up and mucking about with trailer brake release knob in dash. Coincidence of not i do not know yet Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/4/#findComment-501390 Share on other sites More sharing options...
Joey Mack Posted June 26, 2022 Share Posted June 26, 2022 you are doing the best you can,, just be aware of wasting your money at shops.. You seem to be be quite smart... rely on yourself just like you are doing.. I beleive you will fix this issue.. try to isolate the truck from the trailer, to help in the repair. are you able to hook shop air to the truck, so that it isnt running, and making a lot of noise while you look for the issue? im trying sir, even though I said I was 'out'... i guess i;m never really out.... jojo 1 Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/4/#findComment-501392 Share on other sites More sharing options...
The Nitro Posted June 26, 2022 Author Share Posted June 26, 2022 I can plumb my air compressor into wet tank somehow and see. Theres a coupler coming out of wet tank that was probably used to pump tyres in the past. I’m listening to everyones replies and picking out the logical ideas to check and try that fit in with my own understanding of how things might work. I’m not rushing off to parts store for every idea I hear online but at the same time I know theres a lot smarter guys here that me with more experience. The cans on trailer are looking very old, I can see inside peep hole the rubber is perrished a bit (still work) and the cans on trailer are 20/24 same as on truck. The new cans i bought will go on trailer instead when i find my problem on truck. So no loss there as trailer definitely needs new cans anyway. The problem will be found one way or another but taking it to truck mechanic is not happening. I couldnt sleep at night letting another bloke find this simple air leak it would make me feel useless hahaha Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/4/#findComment-501395 Share on other sites More sharing options...
Joey Mack Posted June 26, 2022 Share Posted June 26, 2022 the coupler on the wet tank, will allow you to charge the air system.. good deal.. Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/4/#findComment-501396 Share on other sites More sharing options...
Onyx610 Posted June 26, 2022 Share Posted June 26, 2022 You can take these valves apart and clean them up and re grease them. Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/4/#findComment-501397 Share on other sites More sharing options...
Joey Mack Posted June 26, 2022 Share Posted June 26, 2022 you can take a red glad hand and screw a shop air line nipple into it and hook it to the trailer, and charge the trailer, without the truck and test it... the trailer can also be the issue, if the issue exists when hooked to the trailer.. either way, it would be good to test the trailer, since you just said that it happened when the trailer was hooked up.. jojo Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/4/#findComment-501398 Share on other sites More sharing options...
The Nitro Posted June 26, 2022 Author Share Posted June 26, 2022 (edited) The leak happens with trailer connected or disconnected so I think its on truck side but the trailer cans do need replacing after I fix the truck. The comment about dash brake valves could be relevent still as that red button for trailer brakes would not have been touched/pulled for perhaps 10 years as previous owner didnt have a trailer on it. Ive been using that button so if its somehow connected to engine off or on or feeds the park brake valve or the unknown valve i showed with green and blue and orange lines then we might be onto something. I will dissasemble the park valve and unknown valve and look in them tonight after work if i can Edited June 27, 2022 by The Nitro Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/4/#findComment-501400 Share on other sites More sharing options...
Joey Mack Posted June 26, 2022 Share Posted June 26, 2022 yellow button is for the power unit, ie: truck tractor,, red button is for the trailer.. Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/4/#findComment-501401 Share on other sites More sharing options...
The Nitro Posted June 27, 2022 Author Share Posted June 27, 2022 Rang the local truck parts guy and sent him pics of both valves and hes got em in stock. Ones called a kidney valve he said but wasnt sure exactly what it does Haha. Anyway the yellow hose thats leaking into service brake valve from spring brake/park brake valve is called the equalization port from what I can tell. He said its a couple hundred bucks for the 2 new valves so thats good hes got em if I need em. Truck needs to be on the Rd again by the weekend to deliver about 50 tonne of cow feed to a bloke that needs some. Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/4/#findComment-501416 Share on other sites More sharing options...
The Nitro Posted June 27, 2022 Author Share Posted June 27, 2022 (edited) Might of found the problem. The big oring on park brake valve is buggered. That would let air from par brake go past and directly into yellow hose leading to service brake and out the flap. Never mind the other stuff Joey, thats just a nosecone, supersonic De larval nozzle, altimeter and dual deployment with redundancy backup parachutes ejection system I’m building for my rocket 😂 Edited June 27, 2022 by The Nitro Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/4/#findComment-501420 Share on other sites More sharing options...
The Nitro Posted June 27, 2022 Author Share Posted June 27, 2022 Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/4/#findComment-501421 Share on other sites More sharing options...
The Nitro Posted June 27, 2022 Author Share Posted June 27, 2022 The check valve up in cap isnt real good either. Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/4/#findComment-501422 Share on other sites More sharing options...
Onyx610 Posted June 27, 2022 Share Posted June 27, 2022 (edited) “Kidney valve” is the spring brake relay valve. The one you have apart is the service brake relay valve. The little valve with the red line and green line is just a double check valve. That valve on the cap of the valve you have taken apart is the “anti compounding valve” prevents a double application of braking power when the parking brakes are applied and you press the brake pedal. It could be part of your issue. Edited June 27, 2022 by Onyx610 2 Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/4/#findComment-501424 Share on other sites More sharing options...
The Nitro Posted June 27, 2022 Author Share Posted June 27, 2022 Good to know thanks. Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/4/#findComment-501426 Share on other sites More sharing options...
The Nitro Posted June 27, 2022 Author Share Posted June 27, 2022 (edited) The valve that I just showed apart has the 2 discharge ports and they go down to T pieces which then feed the 4 cans ports marked “spring brakes” so I’ve been calling it the park brake valve but didnt know the exact name for it. The first valve I replaced when this problem started at start of thread (one with leak out bottom flap and green hose on cap marked “signal” has its 2 discharge ports leading to T pieces that feed the 4 cans ports marked “service brake” so I was calling that leaking one the service brake valve as pushing brake pedal sends air down green signal line into the top of cap of that valve Edited June 27, 2022 by The Nitro Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/4/#findComment-501427 Share on other sites More sharing options...
The Nitro Posted June 27, 2022 Author Share Posted June 27, 2022 Pulled the kidney valve all apart which is the one that changed air leak sound from flap on other valve when I hit it with hammer and it all looked ok except for a small bent rusty almost broken fine wire spring and rubber flap valve in the “con” port. Very rustly and corroded inside this port and suspecting the flap not sealing properly behind spring. (No idea if that port is linked to the problem or not) orings seemed ok in the rest of valve. will replace both valves I think and see. Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/4/#findComment-501429 Share on other sites More sharing options...
Onyx610 Posted June 27, 2022 Share Posted June 27, 2022 Even though you may be replacing a lot of parts to find a leak, the learning experience is worth every penny. Your doing a good job. 🍻 1 1 Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/4/#findComment-501433 Share on other sites More sharing options...
The Nitro Posted June 27, 2022 Author Share Posted June 27, 2022 There has been lots of things to learn about on this truck since i bought it. the guy i bought it off knew it needed a lot of repairs and he couldnt fix anything himself and always took it in to the shop. After This air leak is sorted out I might need to help to learn about a few other things that I think need fixing on it. like the shiny universal end cap thats spinning in the front drive diff yolk and maybe the bouncing up and down front end like its got a square wheel and maybe the leaking muffler and the rear airbag/geometry height if you guys can tolerate my ramblings as work through those hahaha thanks guys Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/4/#findComment-501458 Share on other sites More sharing options...
Onyx610 Posted June 27, 2022 Share Posted June 27, 2022 🤣 keep them coming, we will be here… Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/4/#findComment-501459 Share on other sites More sharing options...
terry Posted June 27, 2022 Share Posted June 27, 2022 You can cut a shim out of a beer or pop can to tighten up that u joint cap, if the rest of the u joint is ok. Terry 2 Quote Link to comment https://www.bigmacktrucks.com/topic/69911-air-leaking-out-of-bottom-of-this-thing/page/4/#findComment-501461 Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.