Hi I have an Longong 10 t wheel loader Z30 with 390 total hours, though I have had it for 7 years. The brakes often "loose all air" when applied, the air comes from the foot pedal region and needs to be pumped a few times to stop the leak. It is annoying but not the end of the world. After you pump it a few times, it re-seals and all is good. Over the past few days, the brakes have lost all "power" so to speak and are insufficient to stop the vehicle if on any slope. That is when the brakes are applied, the vehicle barely notices the brakes are on, though they are coming on as the vehicle will stop if on flat ground. After scaring myself today I have parked up the vehicle and decided not to use it again until I fully fix the problem. The problem really manifested itself today, but has been there for a couple of days. Does anyone know much about the breaks on these things? I am guessing there is a seal that gets stuck and causes the rapid outrush of air and perhaps this has got to the point that the air escapes rather than compressing the brake components. I wish I could get a proper service manual, but all attempts so far have been fruitless. Part of the problem with buying out of China I suppose. Any suggestions or ideas would be much appreciated, cheers
I am new to this forum and new to heavy equipment in general so by all means take my suggestion with a grain of salt... and not as expertise Also I am not familiar with the specific machine you're referring to. Could it perhaps be a leaky/faulty brake treadle valve? I mention this only because I recently replaced a brake treadle valve for leaking air on a CAT 930 loader that I've started working on. Perhaps you can have an assistant spray the foot valve area with soapy water while you apply the brakes so as to pinpoint the air leak? Just my novice thoughts however!
Thanks SAT25 Do you normally replace the entire treadle valve or do you buy kits and refurbish them?
I think you can do both actually. However I found it easiest to just replace the entire valve assembly. When I went to the Catapillar parts department they had a diagram that showed all of the parts within the treadle valve and called all of those parts a "brake group ". Each of those individual parts within the "brake group" could be ordered on it's own, however since I didn't know exactly what specific part was faulty and since more than one part was likely bad I wanted to rebuild the entire thing so I ordered the entire "brake group". When the "brake group" parts arrived, it turned out to be a fully assembled replacement treadle valve. That was fine with me! The complete valve assembly was around 230 bucks. Of course your particular machine maybe completely different, I don't know… I would suggest pinpointing the exact source of the leak before replacing the valve. If it's anything like the Catapillar treadle valve there are several airlines attached to it with fittings. It's possible one of these fittings maybe slightly loose and leaking. Start with the simple stuff first.
I just replaced a set on a 936 cat,they are not worth rebuilding,got remains for $36.00 each.Problem is the cat ones are bendix and the china ones are ???Best. Bet is to find the leak and start there.
Ok, thanks, it sounds like the loss of power is related to the leak, I so wish I could get a parts manual so I new what I was looking at......
Do you know if your system is air over hydraulic? Inboard or outboard brakes? Pads or shoes?
The are 5 disks, one on each wheel and one on the central drive shaft. All the pads are unworn, though I suppose they could be glazed, Interesting question about air over hydraulic for the brakes. I have been over the complete unit to change all the oils and have never noticed any brake fluid containers, but with the disks I would have thought that they would have to be hydraulic, the feeders to the brakes are small bore tubing which would be insufficient for air (not that I have ever seen air drive disks). Plus air is compressible which may not work to well on disks..... I suppose I am convincing myself that it must be air over hydraulic? I must look into that more closely. Oh for a proper manual.....
Follow them back to the master cylinders.There will most likely be a couple of air cylinders driving them.The way the Chinese copy stuff,the air treadle valves may be a direct copy of bendix.BTW mine used a pair of E3 valves.check ebay for a picture if you need one.
Let your ears lead you to the leak. You said you hear it leaking from the pedal area, and that's right where the treadle/foot valve will be if its anything like the CAT I'm working on. On mine there is also what appears to be a stop lamp switch attached to a fitting on the treadle valve that is leaking air when brakes are applied. That's why you need to pinpoint the leak because it could be leaking from something attached to the valve and not the valve itself. Or you may have more than one leak like I found..
SAT25 The leak that is audible is the intermittent leak and goes away when the pedal is pumped a few times. I have turned off the machine as listened closely, there is no audible leak or it if I listen when its dumping all its air (because I chose not to pump it a few times but quickly shut down and climb out and listen) it comes out the blow by filter under the valve, the same place as air normally does when taking your foot on/of the brake. That's the surprising thing about the loss of power of the brakes if that makes sense, so while it is probably related, I am not losing air when the brakes don't work and the pressure gauge still in the green above 0.4Mpa and less than 0.8Mpa. When the huge leak happens, the gauge drops to close to zero, there are no brakes at all until I pump it. The air pressure gauge jumps back to whatever is left in the tank when the valve reseals.
That would seem to indicate that master hydraulic cylinder is empty.When you find it, be sure to check for the type of fluid that is in it. Some take brake fluid, and some take hyd oil,dont put in the wrong stuff! that will wipe out all the rubber parts in the system!
Id replace the foot vale aka treadle valve, they are usually very common valve you can get at your local truck parts store for large semi trucks. Then see if your brakes work obviously check your brake fluid ect maybe bleed the brakes shouldn't be impossible. Sounds like it sits a lot and brakes tend to go to hell when they sit for long periods.
Thanks for that yes 390 hours in 7 years means it is idle a lot of the time.... Sound like the best course is to 1) check brake fluid (duh!!! - I should be shot for that one) 2)take off treadle valve so I can find something similar 3) reinstall treadle valve and bleed brakes if fluid is low.
Yeah take that treadle valve to a semi truck parts place I'd almost bet they have one if they don't get the part number for it from their book and Google it ebay has a ton of stuff like that. I bought 700$ worth of bearings and races for my clark 55b on ebay for 173$ hehe
Well got to laugh. Both brake fluid containers empty......The machine is parked in a garage on a concrete floor. No leaks at all, I wonder where it went! Now for the treadle valve.
It will probably leak when you get them bleed and pressure up the system ya know
No sign of leaks at all.....brakes work fine, but need to fix the intermittent treadle valve issue. I note the treadle valve has two O rings, I wonder if it is worth replacing them before embarking upon a new complete valve.
It's probably cheaper that way to replace the orings but the valves are really cheap and it's easy to just do the whole thing
The hard part about replacing the whole valve, is clocking all the angle fittings to just the right spot so you can get the tubes started!
Yup should be able to pull the foot peddle off and then remove the valve from the bottom take it out get new valve take pics or draw lines on the old valve and remove one fitting at a time and move them to the new one. I've done a ton of these valves
When replacing the treadle one thing that will help ease the install is do not tighten any of the line fittings until you have all of them threaded into the valve and then have the valve itself mounted in place. Once that is all done then do the final tightening of the line fittings.
Well thanks everyone. I took of the treadle valve and then could not help myself, I took it apart. It was pretty dirty on the inside but all the o rings were fine. I cleaned it all up, re-assembled it and it now works fine! Its interesting how much rubbish was in it, but none the less I I have working brakes again!