Hello guys. We were forced to take out the rear axle of our backhoe due brake fluid was getting to the diff. So we removed the tires and lifted both stabilizers to the max. Then I put a wheel bed below the axle and took it out. Here are some pics As you can see the o-rings are square. I put some water to the piston and is leaking. I call Finning and the have the square o-rings so we'll get the round ones somewhere else. Discs look good, just the problem was it was always running out of brake fluid. Tomorrow I'll put more pics
Hello again Coming back with this issue. So we changed seals (for the round ones, viton) and after 3 months the brake oil is going again to the differential. Can`t believe this thing. Have you guys encounter this problem? It´s not about installing, I think it´s about seal material
I'm not sure what the issue is for sure and I don't think you will either until you dis-assemble it again. The times that I have replaced the brakes on my 416C they lasted about 5,000 hours before the oil started going into the differential. I used all OEM parts, including the o-rings. I thought that I had replied to a previous thread regarding the things I had done during the previous (2) times I have done the brakes on that hoe. Regardless, I will expouse the limited information that I have here. I am not a mechanic. I am an excavation contractor and the mechanical experience I have is from being a "shade tree" mechanic, for my own equipment. As you may already know the piston is very hard to put back together. It is very easy to cut the o-rings when you re-assemble them. I used several sets of seals, and several attempts, to get the job done without the seals getting cut. I was sure to use assembly grease and I also allowed some time for the seals to contract after streching them to get them into place. Obviously it is very important to make sure that the square seals are not twisted but I would say this is also true for rounds. The tip that I got from my local Cat dealer was how to check the seals prior to the axle being put back into the machine. Once you have the brakes re-assembled, and in the axle housing, begin re=assembly of the axle housing to the center section of the diff (this is critical as the brakes can come apart if you don't). Get the axle shaft into the diff, and push the housings together. It might also be adviseable to install a couple of the bolts. Once this is done apply compressed air to the oil port (found on top of each of the axle housings-the holes that the brake lines are connected to when fully assembled). You should hear the brakes clunk, as they apply, but you should not hear any air escaping from inside the axle housing. If you do, you have a seal failure. Most likely you have cut the seals during assembly. Once you have done this, without any air leaks, to both sides you can replace the rear axle back into the machine with confidence. As far as your specific issue, a few things come to mind. You have not said how many hours are on the machine. I am left wondering why you did not replace the brake pads. Even if you put everything back together, without cutting the seals, the brakes will leak if they are allowed to get beyond the service limit (the piston leaks because the worn out linings allow the piston to travel too far. The seals reach the end of the bore and the oil gets by and leaks into the differential. I would think that the square seal has a wider groove that it rests in (the square seal is wider thus allowing a larger contact area). Maybe this extra space will allow the o-ring to roll during assembly. I also wonder if an o-ring would be more "proud" if it was big enough to fit tightly in a groove that was designed to house a square seal. Furthermore, if you have installed an o-ring, instead of a square seal, does it not perform as well, in this application, thus allowing the seal to fail prematurely? Lastly, is it possible that you have employed an oil, or additive, in the rear axle that has attacked the seal? As I said, I am not a mechanic but these are the things that I would check out.
When installing I tried the air test and went fine. Machine worked fine for 3 months and then brake oil started to go thru diff. Brakes discs are new
OK. Well, I guess that I had already offered that tip. I still wonder about the performance of the round o-ring in the groove that is designed for a square seal. You did not comment on the possibility of the oil not being compatible with the seals. I could easily imagine that you used a compatible oil but I am not in Chile, have no idea what is available to you, and you have reached out to the forum, instead of the local Cat dealer (if one even exists), for assistance. All these factors, including the short term success-long term failure of the seals, makes me wonder. Are you planning to dis-assemble again? Please keep us posted.
what oil are you using in the brakes?Oil recomengation is hydro 10W
We used the recommended CAT oil. Round or square seals have same results, both last 2-3 great months but 4th month they die
Another question. What oil are you using in the rear axle..? I suggest that you take a close look at the seals when you disassemble the next time. I've seen lots of Cat brake piston seals get "shaved" (in other words the sharp corner of the housing removes a really small piece of the seal for maybe 60 degrees of its circumference) when installing the piston in the housing. It's really easy to do, and the brakes will work perfectly initially (air test, etc). However after a short time the seal will blow out where it was damaged during assembly. Seems a silly question but are you sure you got the correct parts..? I would have thought that the circular section piston seal should have a Teflon-type back-up ring behind it.
You know what, I think that is the problem the teflon back-up ring. The ones we got were just the round seals.
Nige, do you have a picture or service bulletin for the teflon back-up ring? I asked these Finning guys and they said to me:"we just have the o-rings"