Hi guys im new here i want thank for accept me in this forum, now i explain my problem. i have a 988b and have a very strong oil leak in front of transmission, (under cabin) y already changed more times than i can remember brake acumulator, it fix the problem for few days but later again i have the leak, now i changed again the acumulator, and leak is now behind the round cover used to be, i changed again acumulator and same problem what else i can do my brain doesnt work anymore please i aprecciate your help
in this image i can explain a bit better, first was in front round cover now seems to be in middle of the same part
If you are referring to the round cover with the orange & white sticker on it in your photo, that is the parking brake ............... and before you ask there are seals for each of the three parking brake pistons behind that cover. Are they leaking maybe..? Here's what's behind the cover. The brake piston seals are reference #27
thats correct i speak about that cover, i open it and behind there are 3 cylinders and in center a kind of gear, when machine works used to leak from the front cover (the one with the stiker) now is leaking from the middle of the part now not from the cover
Maybe your leak is in the lip seal (ref #19) that seals the rest of the transmission from the parking brake compartment..?
ok this image helps me a lot and yes maybe thats the problem, now i need find how to thake this part out without takeing down all transmission
really Nige thanks a lot this image helps me too much, if you know the way to take this out without taking tranny down i apreciatte any suggestions
You now have 5 posts so you will be able to send and receive Private Messages (PMs). Send me a PM with your email address and I will happily forward you the disassembly procedure for the parking brake. Be aware that the manual procedure calls for the removal of the brake from the transmission and to do that with the transmission still installed on the machine requires the cab to be removed. You are probably going to have to invent your own procedure if you want to do it any other way. From what I can see there should be no major issues to disassemble the parking brake right on the transmission, except you'll need to take care getting the piston out and back in again if the parking brake is not lying flat on a workbench. If anyone else knows anything different, chime in please ............ Also be careful with that brake, it has some extremely powerful springs in it ...........the manual procedure carries all sorts of warnings regarding disassembly.
i cant send pm yet my friend
You should be able to now. Click on my User name and a small window will open. Click on the "Private Message" and away you go.
already sent my friend
by the way i have this machine 5 hours away from my workshop in a marble quarry and dont have a closest town is 2 hours away from machine so i apreciatte all the help before i go again
We disconnect oil line, remove bolts 32, with some carefully set straps we ( manhandle ) it down out, two guys and patients. Does it leak when you release parking brake? Lots of fluid. Once its out it not difficult to reseal, make sure housing ( 12 ) isn't cracked.
thank you overworked, by the way here are some pics of the oil leak my operator just sent me
Is that with the parking brake applied or released..? Could be a cracked brake housing like Overworked mentioned.
As Nige asked, is brake on or off, oil only goes to brake to release it, so if it stops leaking when you apply the parking brake it is a brake leak, with button pushed in to release brake it will leak as long as the engine is running till it runs the tank out of oil. Leaking out the back its probably a cracked housing. If it were the seal of the input shaft for the brake to leak that much while sitting still transfer gear housing would have to be way full of oil. If piston seals were leaking it would run from gap at cover with sticker.
its without park brake, all time since you start machine has this"new leak" and doesnt stop, and i say new because before as overworked said, first strong leak started from cover, i fix that leak just changeing brake acumulator that is behind the cabin left side, (i dont know why, but when i changed acumulator oil leak from cover with stiker stoped) it worked maybe 1 week and now i have this other leak
Try blocking the line that brings hydraulic oil to the parking brake. If that stops the leak then you know it is coming from inside the brake. Just don't try to move the machine in this state because the park brake will not release. If your leak does stop then you know you have one or more of the piston seals blown inside the parking brake. However it does raise another issue. With the parking brake control in the "ON" position there should be no pressure in the hydraulic line to the brake, so why would the brake leak if the control in the cab is in the on position..? The only thing that I can think of is an issue with the hydraulic control valve for the parking brake that is causing it to remain open all the time, thus causing the parking brake to receive oil pressure as soon as the engine is started.
Might be just the angle the machine is sitting on letting it leak there instead of from the cover plate with the sticker. Not saying it never happens but I've never seen that housing cracked. Most of the failed brakes I saw over the years from back in the early 1970's have been the pressure plate and the backing plate from people moving machine with brake on and the warning alarm not working. Either way it needs to be fixed, shame about the remote location, only good thing is about the only tools needed to remove should be some 3/4 inch wrenches and sockets and maybe a 7/8 or 1 inch wrench for the line. And of course a strong back on the strap. A good pressure washer would be handy too! Make note of the three wires on the pressure switch, assuming they are still hooked up. If you need part numbers let us know. Good luck
monday i will arrive to check this equipment and before i start unistall all parking brake i will do these test, ok for more info i will tell you all what i have done to that machine. Problem machine doesnt move forward and has no brakes and leaks oil from front cover(number 6 i think) solution changed brake acumulator (worked 3 months) problem oil leaks from front cover, but still moves forward and has brakes solution changed again brake acumulator (i serviced the old one i take out) worked 1 month problem oil leaks from front cover (a lot) solution again change brake acumulator (again the other after i serviced ) worked 1 week and now i have this leak that is not the usually i used to have
Are you taking any pressures? Brake, accumulator, are you loosing nitrogen? Recharging? The more info we get the more we can help. Serial number? Those pictures were dead on. When you say no brakes, is that park brake or service brakes?
no i havent tracked pressures, nitrogen is ok and when i say no brakes it was normal (service) brakes not park brake, now it works all perfect forward and brakes but the leak changed position, the serial number is 50w346,
Like said above, disconnect and cap off line and recheck.
ok thanks my friends I really apreciate all your help i was tired and my brain was becoming crazy about not find the cause for this problem,
Guess I'm a little confused here. If there was no brake as in parking brake holding I don't see how changing or charging the accumulator would make anything different. Yes the oil pressure to release the brake comes from the accumulator but the apply pressure to lock on the brake is from the springs in the parking brake. If something is leaking in the brake there are only a couple things that could cause it. One is a cracked housing like someone else suggested the only other thing would be damaged seals on the three pistons. Nothing you can do to stop the leak short of removing the brake and disassembling it to find the cause. That is "if" the oil leaking is hydraulic/brake oil. If it was transmission oil and it was coming out in a steady stream as in the picture there would be two problems. One being the lip type seal behind the brake and the transmission was way over full.
well hansen thinking a bit and studing images from Nigel i think the cause can be the retainer (or seal) (19) for that reason leak oil from middle not from back
The problem with that theory is that it would require the transfer case to be full of oil right to the top, and that is not going to happen - ever ............ Try blocking the line to the parking brake as a first step and let us know the results. if you have not done any pressure tests how can you say that the nitrogen charge in the accumulator is correct..? Surely you need a pressure gauge and a nitrogen test kit to correctly charge the accumulator after overhauling it. Personally I think there is potentially more than one problem here and it's going to be a case of working through everything logically to figure out what the problems are. I strongly suggest you get hold of both a nitrogen charging kit and a full set of test gauges covering everything up to 3000psi plus a set of fittings, because once the problem of the leak from the parking brake housing has been solved, plus the accumulator precharge pressure has been checked then it's going to be off into the braking system checking pressures and that will need a set of test gauges.
OK that makes sense, but if you have that much oil leaking from the trans with it sitting then something is overfilling it, declutch valve maybe?
We can figure this one out really easily. Pull the dipstick for the transmission - where is the oil level, correct or waaaaaaaaaaaaaaay high..? Also with so much oil obviously leaking externally, are you adding oil to the transmission or to the hydraulic tank...?
ok guys operator just sent me these pics; now again start trow oil from front cover as you can see
im adding to transmission where all oil go down my friend, and please check the pics i just posted in previous page
i dont know if i start paranoid but in this pic looks like housing is broke
by the way operator of the machine just told me the park brake doesnt work and this is maybe like 8 years ago and machine was working good until this problem started
I agree with you that "hole" on the parking brake housing does not look correct. I think the parking brake is going to have to come off simply to discover where the oil is coming from, especially as you say you are adding oil to the transmission.
Huh? the parking brake has not worked for 8 years????? Not to be a jerk but where hell is MSHA when you need them? I/we would not run a machine for 8 minutes with the parking brake not working, just long enough to get to the shop to fix it! Is that oil flow in the picture there with engine shut off? Does it only flow when the "non-working" parking brake is in the release position? We really need to get some answers to some of the basic questions. Believe me these parking brakes are a very simple design and work well for years with little or no problems but when things like warning alarms are not kept working and untrained operators are running them they can get expensive fast. I would not spend any time thinking about that "hole" may or may not mean any thing. It is not in my opinion in any way the cause of the leak, no oil should be in that area to begin with, actually I seem to recall one or more notches in the housing possibly to let water or dirt out. As Nige says just pull the dipstick and check the transmission oil level. DO NOT fill to the top with cold oil it will come up quite a bit when it gets warm. Have you checked the breather/s on the transmission and or converter housings? Some have one on each others have one on a tee with hose leading to the other compartment. Again like Nige says, no matter where or why the oil is coming out the brake has to come off to fix it! Pull it off clean it up and inspect everything. Also remove the splined inner hub and it's seal, even if it is not leaking now one would be crazy to get that close and not do it.
Not hansen when machine is off doesnt leak a drop, but when you start the machine begins the fountain of oil. and of course parking brake is in the relesed position (all time) about MSHA well this machine is located in mexico and thats why they dont care about nothing, no safety regulations and nothing they can be afraid of. yes i will take out parking brake monday morning and fix it also i will check why parking brake is not working and also fix it, and as you say, i will change splined inner hub seal, if im going to take the parking brake its very stupid dont change it also. to all you guys THANKS A LOT
One of the "basic" questions I mentioned. Why was the accumulator changed? Who or what gave you the idea that working on the accumulator would have any effect on this leak? Not to be a jerk again but are you sure you know what and where the accumulator is located? It is a thing that looks like a hydraulic cylinder with no rod coming out the end and is located behind the cab under the floor panel on the left side as sitting in the cab. It is about the simplest items on this or any machine. As I said it looks like a hydraulic cylinder and that is just what it is just a tube with a solid piston with seals inside. There is a fitting on the top cover similar to a tire valve through which nitrogen is put in under pressure. Then at the bottom there is a hydraulic line connected that comes from the accumulator charging valve. When machine is started the oil from the charging valve pushes against the piston and compresses the nitrogen. Then when pressure get to the right point the valve stops the flow till the pressure drops to the cut in pressure. This is just like the operation of an air governor in an air brake system, just using oil under higher pressure and nitrogen as the compressing gas. With virtually no maintenance they will last for years or decades with only a recharge every year or so, seems ones that sit unused for long periods of time will need recharging a bit more often. In over 44 years of working on Cat loaders with this style of accumulator, dozens of loaders starting back in the 98887A days, only recall needing to reseal one of them. That's why I question you're statement "already changed more times than i can remember brake accumulator".
Well right there is why there is an MSHA, if company owners cared about the safety of their workers in the first place we would not need MSHA! I will not argue that MSHA or any other government safety organization does not go too far with some rules, but if people were not getting killed or maimed at the rate they were back in the 1950's and before from management trying to squeeze every penny they could out of the workers we would not be dealing with them today. Enough time on soap box! Sorry about the rant. While you are down looking at the loader make sure the cable for the parking brake control is working nice and smooth and free, if in doubt replace it! I would hate to see you fix the brake and then because the cable is hard to move let the valve stay in partially applied position and cause it to fail a week later!
hansen, its the first time i try fix problems in a 988b transmission, usually my work is with dozers excavators, graders, and backhoes, in 988b i just fixed the engines and no more, so when this problem started i was blind working and started check all valves, and all the parts (i think have some efect on the behavior of machine) let me explain why i arrived to that part. when machine was not moving front and having the leak the first thing i did was check magnet filter under transmission and the fliters elements that are behind the cab, both was broke and full of **** (they told me they havent changed them more than 4 years ago), after that and following the output for 1 of those filters i saw was direct conected to a valve (later i knew was the brake acumulator) i took out the acumulator and disamble all clean from all the dirt broked filter oil send to him and install again (also other mechanic before me try fix and of course had some parts missing exp the 9 balls it needs to have was only 5 and things in that style) also plugs and stems was like rusted in black, after that, machine worked good (no idea why worked good) when i have again the problem (and knowing almost nothing as i told you about this transmission) i did again what it helped me before, and that was again change and check acumulator i took other acumulator from other machine and again worked good and as i told you i dont know why but stoped the leak, (well in this inter of the oil leaks i changed 1 and other acumulator and always seemed to fix the problem) this wensday they call me again telling me that oil leak was not now from front cover that was in the middle (the first pics i posted) and of course after that i became crazy and dont know what else to do, after that i found this page and thats the history of this machine
the operator just called me its hyd oil what is leaking
Back to the parking brake then .......... Either way you slice it - it has to come off
Like Nige says, that brake has to come off! Once you get it off and on the bench you will have little trouble seeing what the problem is causing the leak! Hope you have an old pair of coveralls as that is going to be a nasty dirty job from the looks of the machine. I can feel your pain when you mention some other "mechanic" having been in there before you, never know if parts are back in the correct order. But at least you seem to have a parts book to go by. Just to be 100% clear the valve that you posted in the page from parts book is the accumulator charging valve. The actual accumulator is: Been a few years since I had one of those valves apart but seem to recall getting the spool with the 9 balls in it back together is a little tricky, a little dab of grease on the balls seems to help a lot! Please don't think I was blaming you for the machine being run with brake not working, I know how too many owner/managers can be! I like your quote :Some days I hate be heavy equipment mechanic and want quit my job, but when a machine runs again my heart jumps and I remember why Im a mechanic I'm sure you will get this one working again, feel free to ask questions and post pictures of what you find. You can PM me too if you like. I have access to SIS so I could send you more information if you don't have a service manual or maintenance manual. Ken
Thanks once again guys tomorrow i go quarry and let you know what happens
What I would suggest is to approach it logically. OK, so we know the parking brake is leaking hydraulic oil as soon as the engine starts. 1. Block the hydraulic line to the brake. If the leak stops then remove the brake assembly and fix it so it doesn't leak. 2. Once you have the brake done you have to find out why the hydraulic line has pressure in it as soon as the engine starts. It should not be like that, it should only have pressure when the park brake valve in the cab is moved to the OFF position. So maybe some disassembly of the valve might be necessary to find out why. 3. After fixing the above then I would suggest a full pressure test of both parking and service brake circuits (including accumulator precharge pressure) may reveal other issues. Often blown brake piston seals can be the result of something badly adjusted somewhere else. I realise that it will be much more difficult to do all the above than the text appears..........
guys Fisrt of all Merry chrismas to every body and best wishes second i went to the quarry for check the parking brake, when i separate the parking from tranny the first 3 problems appeared, 1.- the shaft of parking brake remain in the housing from transmission. (see pics below) 2.- seal and ring (19,20) complete destroyed 3.- bearing really bad when i separeted this morning the housing same history but worse seals like paper broked, botls missing from housing and the 4 that still remain in, for trow to junk yard and the worst all discs was broked and they looked like doritos the only good part housing is ok the "hole"looks more just like a drain than a broke part
more pics
Not to put to fine a point on it but that's fcuked......the park brake I take it..?
Yes Nigel, is all fked up, now we know why was ttrowing oild like crazy
Kind of looks like I was expecting! Guessing problem might have started by someone not releasing the brake and driving off. That's the problem when warning alarm is not working and or operator not familiar with a machine. We had a similar problem years back with the same brake on an 87A 988A. That time the brake got hot enough to catch fire. Besides brake had many hoses and wires to replace. Good thing is it is an easy fix, only need two things to fix it. Time and money! Mostly money at this time! You are the mechanic not the owner ,Right? If you need any info like part numbers or assembly instructions send a PM or post them here. One hint that could save problems down the road. When You reassemble make sure that plate with the tags on it is positioned so the three release bolts can push against the inner housing to release the brake. I had one that was assembled wrong and only two of the bolts would hit the housing and not let it release. Only a problem if you need to move a disabled machine.
Be careful assembling that brake, some and likely yours can have the outer plate installed one bolt hole out 1/6 turn out and placing the 3 release forcing bolts in the wrong position. The brake can be released but the housing will be broken. Later Bob
Thanks a lot guys and merry chrismas
the only thing i see diferent in the image Nigel posted before is the seal (17) because here looks is in the center of housing, and in the 1 i separate is an Oring in the outside of the housing
17 is an oring(Cat often refers to orings as seals) Right next to the ball beaing in the housing , looks like #19 in Nige's image is a lip type seal. As bad as the brake disks are I'm wondering if the housing the bearing in is still usable? If it's not real bad might be able to have a machine shop take off a few thousandths. I would tell them not to take off enough to clean it up 100% just get it close, maybe 80%. From past experience s cracked and not usable. So it looks like new pressure plate, brake disks, bolts, all seals and orings, and springs. How do the three pistons and their bores in housing look?
everything in housing is ok but of course i need change everything on that, seals, retainer, orings, bolts, by the way kwn i pm you already
happy new year guys!!!!!!!!!! im waiting for the parts, should arrive on monday
Did I send you the directions on assembling the brake? Seems I did but just want to be sure you have everything for Monday.
Yes Ken already arrived thanks a lot
hi guys and soeey for this delay answer. i already change everything, but still have a leak, as Nigel said y check w/o hyd intake and works great, so the problem is the housing, now machine doesnt brake so i think some stupid (or close to that) used park brake as brake from machine, my cuestion now is where the oil pressure to brakes makes the istersection thanks for all the help
When you say "the machine doesn't brake" I take it that you mean the parking brake is still not working..? Where is the oil leak coming from now..?
Nigel, hi, nice to see you, let me explain what i did for test, i assamble and dissamble 4 times park brake (i was thinking my ensamble was bad when i did it) and oil still leaked, after that ( and 1 thing for all guys who separate park brake, you can do w/o separate fuel tank its hard but possible) later i just left shaft(21), base (16) and seals, and cancel (cover) intake from hyd to park brake, and worked w/o leaks, but didnt brake at all, so now i ask housing to dealer (because there is the problem)but i saw also somebody used park brake as brakes for machine, so im sure somebody,somebody moved a hose before. what i mean is machine is breaking with park brake not with wheels
Ah ha ....... so it would appear that maybe you have some crossed wires (or hydraulic lines) in the brake system ..? Have fun with that .....!!
If they crossed the control from wheel to park brake i think they had a problem with the wheel brakes
that thought crossed my mind also ...... this could be opening a huge can of worms by the time it is finished.
well my friends finally machine its working great all bakes fixed thanks a lot for your help
now i have a problem with other 988b sudenly started trow white smoke from oil filler cap and breather what it can be?
smoke from exhaust is normal but from oil filler cap, brather and dipstick trows white smoke can it be a prechamber? or broken rings?
Is there a lot of creamy sludge on the dipstick and filler cap? That would indicate coolant in the crankcase. Does the white smoke come out in puffs? Can you hear a misfire? Later Bob
I'd add the question, is it pushing coolant out the radiator cap if it's removed when it is started?
well Ken and Bob, coolant its ok no leak or pushing out in radiator cap, oil is perfect (old but not mixed with water) and i found are compression rings that are broked
Trying to picture the 3408 in a 988B, seems like not too bad a motor to do an in chassis rebuild on. That's assuming you're not doing it outside in the rain or during a wind storm. I believe Cat has or did have "Cylinder Packs" for those engines that came with pistons and rods all assembled in the liners. I believe we still have the special puller that lets you pull the old ones as a unit. Can be a good way to go if conditions are not perfect.