Not very good on Cat loaders so I need some help please. I have a 988 built in 1974 and it will not build air. First of all where is the compressor and where is the governor. The air tank in located on the right rear of the machine under the engine cover. Directly below is what I think is the air compressor but not sure. Any help would be greatly appreciated. thanks Ed
It doesn't have an air system, the tank you refer to is an expansion tank to provide extra air volume to the hydraulic tank. Are you having brake problems? Later Bob
Bob, I thought when I saw the topic that someone was having warmer weather than you or I and wanted an AC unit to work! So Bunky, what is the actual problem or symptoms you are dealing with? A few here who did work on those old horses back they were young fillies. Also how about a serial number for that 87A.......
Well he is from Maryland and the Beltway can't hold all that Hot Air in. Later Bob
No brakes. Sn#87A8825 I looked over this unit for brake resouvoir but could not find any. Looks like the pedals are for air so initially I was thinking air over hydraulics. I have not removed any panels as of yet. Just wanted to get a better idea of what I was getting into before I jumped. Thanks BTW it will be in the 60's today
Look on the dash for a Brake Pressure gauge, that's = to air pressure on air system. There is a small section on the steering brake pump, it pumps oil to the brake accumulator charge and relief valve that maintains oil pressure between 1100 and 1750 psi app and limits max pressure to 2500 psi app. Check manual for exact specs. This oil goes to the brake valve and the accumulator line is tee'd off from it. When brake pressure is up to cut out psi the valve sends the flow to the steering valve and when it drops to cut in psi it sends the flow back to refill the accumulator. Accumulator should have a nitrogen charge of 500 psi when empty of oil. The brakes are Expander tube in each wheel park brake is spring apply oil release on the transfer case. The accumulator is beside the trans valves are under the floor plates in front of you and the front and rear brake lines have one slack adjuster each. Faulty slack adjusters will cause brakes to lock on. Later Bob
I saw the indicator on the dash and it was green. I have no brakes and the right wheel is leaking oil from the backing plate area. This customer is only wanting to get enough brakes to load onto a ship and send overseas. Can the tube to this wheel be capped so not to use this wheel brake? Thanks Bunky
Yes with a penny, then bleed other brakes and it shouldn't go all the way through the hull aand end up in the harbour. Later Bob
I am looking at the brake valve. 2 big lines,1 steel line from bottom, a 3/8 size hose goes to inch control valve and another 3/8 hose goes to another valve that is mounted under accel pedal. I assume this is the steer/brake pump you were speaking. The pressures you were talking about are taken from the brake valve going to the pump, is that correct? And should I measure deadhead from the hose or place a Tee in between the hose and brake valve? BTW these things are a pain to work on especially in the cab area. No room. :-/
Valve under the accelerator is the accumulator charge cut in and out valve, pump feeds it first. That valve sends oil out to a TEE accumulator and brake valve. Accumulator stores brake oil under pressure locked in by the cut in/out valve. The brake valve sends it to the wheels, there is a red knob at the side of the seat to control the park brake. I forget which side/Old timers ????? Stop the machine and pump the brakes many times, if the green eyeball flips to red and back to green when you restart the pump is good. Is there much room left on the ship for some tier4 machines with there intakes plugged with carbon. That's one carbon footprint that should be reduced. Later Bob
I pumped the brakes and the eye never changes from green. The red knob is on the left side of the seat. Nothing changes whether the knob is in or out. I don't know if there is room on the vessel, they are usually pretty full every time they sail.I hate to sound stupid (even though I know I am) But what is the steel line that comes from the bottom of the brake valve? And are the pressures measured from the accumulater at the brake valve via a TEE or do I deadhead the hose with the guage and measure this way? These CATS are definately not for me. I would rather be playing with an excavator. BTW I really appreciate you taking the time to help out.
Have him get an assist to load. Push with a chain back to the pushing machine to reduce liability from a costly overshoot. Then be done with it. Now about the machine there are plugs in the valves to check pressures. I usually was charging the accumulator so just measured it with the nitrogen charging gauge. I think you have no pressure and they have things cobbled up to look green when they are red. Hey that gives me an idea, the man who said "if your woman doesn't find you hansom she can find you handy", yes Red Green he could help. Are you near Possum Lodge???? The parking brake has 3 bolts 1/2" in storage holes to put around and force the brake off, likely done now. If the brake was dragging they would have had a fire and everything behind the cab would be burned. It's been a long time, could show you were to test if I was there but it's a challenge from here. Look for stor boss plugs 9/16" nf thread and try them. Seem to think we talked about a 977 bevel gear shaft a while back. Later Bob
The indicator is definately GREEN. As far as pulling with a chain well that is not an option. These units must be driven onto the ship and they must have brakes.You gotta be a snake to even get into these machines to either work or just get into the operators seat. The ladder is on the bucket lever side of the cab and the other side does not have a ladder. I was hoping that I didn't have to remove the linkage on the pedals (in order to gain access to whats below) especially since it is rusty and otherwise disgusting. I have a feeling that this is gonna be costly and the customer is gonna say forget it and send it another way. When you guys work on these thing do you remove the operators seat and backing?
Yes, flip it up and take off the hinge plates at the front. You can put something on battery to sit on. The LH ladder folds up and pulls down to use, likely gone or ripped off. The machine has one hyd pump and a double Steering/Brake pump. The small section is for brake. If you have steering the brake pump should work unless it has broken shaft of destroyed. Some people take them apart and can't put them back together in 5 tries. Later Bob
Lots of old 988's were driven until they had no brakes.
Like I told the customer...if it was still in good condition they never would have gotten rid of it in the first place. Surprisingly the spring loaded ladder is still attached. Unfortunately there is signs of mice or other rodents under the floorboards. Lots of paper and some chewed wires on th top of the tranny. AnywayI will check the pressures tomorrow and if the pump is not producing I will let the customer know and let him make the money decision. That pump probably goes for about $5000 I would think knowing how proud Cat is of their parts. Thanks again. Bunky
We see alot of 966's that are going overseas. Most of these have brake issues but are easy to fix. The 988's are another thing.
Does it have a vane or gear pump? Later Bob
not sure..why
You can get a cartridge for the vane pump. Later Bob
Too bad on the 966's nice loaders, guess where they are going the like the good old tech. Cat ET? Who needs ET? Bunky, I'm guessing the parking brake also does not work? Just wild guessing but if parking brake is not working it's because there is a problem building brake oil pressure and to get machine to move they installed the release bolts in the parking brake. Nice fail safe brake system when working properly, loose brake pressure and the parking brake comes on just like a Maxi system in air brakes.Main difference is the parking brake is totally separate from the service brakes with the exception of using the same pump for pressure.
Checked pressures and got 1200 psi. Drops to 0 when pedal depressed Then back to 1200 when pedal released. Found that the right side front brake line has had blanks installed to prevent fluid from flowing. tried to bleed but got nothing. I will try again later when I bring a helper.
There should be a big puddle of oil under the machine. The oil goes out and back the same line to the wheels, the brake valve sends supply oil out and then lets it drain off. If there is no puddle then something might be wrong inside the valve. Later Bob
Nothing under the machine. I do not get anything from the bleeders on any wheel. Where does the steel line on the bottom of the brake valve go??
I know it's not the "approved" bleeding technique, but the way I have done these Cat brakes that work off a hydraulic pump is to get somting to wedge under the bottom of the brake peddle to hold it part way down. Then start engine and with a hose that fits snug on the bleeder and a bucket to catch oil go from wheel to wheel and slip hose on bleeder and open and let about a gallon or so of oil out after air stops coming. Close bleeder and go to the next wheel, repeat till all are flowing nice clear stream of oil. If you don't get any oil when bleeder is open there is a problem some where. This model 988 does have brake adjusters if they are bad brakes still should bleed but pressure will drop down more than normal when applied and there will be a major hesitation in them coming on. Follow the lines from the axles and you should find a canister like thing about the size of a half gallon water jug. The line from axle at one end and line leading back to brake valve at the opposite end. It is a fairly simple device, best description off the top of my head is a larger check valve thing. Oil is free to flow in from the brake valve and out to the wheel brake bladders. When brake is released only a small measured amount of oil is allowed to return from the wheel brake. This keeps the brake pads close to the drum but no dragging. If I can get a good picture off SIS I'll add that to the post later. Found a pretty good picture. Note the part they don't really show that is called the "sensing assem" is what controls the amount of oil coming back out. These and the large seal ring around the big piston are what I usually found to be the problem. The upper and lower halves screw together, large chin wrench or make tool from a piece of flat stock with four holes to bolt to the holes for the split flanges. As I recall the "sensing assem" is held in with a snap ring and is also a press fit. Never found a "non-destructive" way to remove. Just remove snap ring then turn housing over and use a punch through the small hole in the center. Press or tap the new one in and replace snap ring. I see where Bob says a bad slack adjuster will cause brakes to lock on, in my experience never had one lock on the brakes but if accumulator charge was a bit low of charging pump was weak brake pressure could drop enough to cause the parking brake to automatically apply. But if some failure did prevent the oil to flow back from the brake bladders it sure would bring things to a halt! Good luck! Just out of curiosity checked availability and price of the sensing assem. Appears it has been replaced by a Piston Kit they actually stock one at our local dealer and it's only $45.32 sounds almost too good to be true for a machine that is over 40 years old!
What happens is the piston doesn't drift down with the oil flow so oil goes through the check valve. The expander tubes fill up and oil can't get out. The pistons need to drift down so they can let the "measured" amount of oil back out and release the brakes while keeping them adjusted. Bunky, something is wrong with the brake valve, sounds like when you brake the oil is dumping off not going to the brakes. Lines might all be ruined aswell. Later Bob
Thanks guys I really appreciate the ideas
Guess we were just "lucky" and never had that failure mode with any of the many we had! And we had many failures over the years most common might have been the little tin plates on the expander tube coming loose and then the backing plates for the linings cutting in to the tube. Brake dust mixed with oil with a helping of stone dust for good measure, and no pressure waser at hand! Can't believe someone would send a machine to auction like that Bunky! I won't say anything about a 988B with a broke off pinion shaft on the rear axle that had a piece of flat stock made into a large finger to hold the rear yoke in the transfer case I was nice and put the drive shaft and yoke in the box on the left rear counter weight
alright. looks like the brake adjuster is shot. THe front brake lines have been terminated with slugs. The rear brakes will bleed but when I try to apply brakes nothing happens But if I keep applying pedal then the expanders fill up and brakes apply. But when I release pedal the brakes release but I then must press pedal in order to build pressure and wheels will stop. I can keep pedal part way depressed and the service brakes operate. So, from what I can see the brake adjusters must not be working. So now where is this adjuster located. ( book does not show locating of rear adjuster) And how hard is it to remove and rebuild. This part is no longer available thru the Cat dealer but rebuild kit is still available. I looked around the rear axle and saw nothing but caked on mud and other crud. Bunky
Hey bunky Yeah sounds like brake adjusters follow the brake lines to each wheel the brake line screws into adjuster should be 4 3/8 thread bolt if memory is correct.
The brake adjuster is stuffed up under the engine near the axle. There's not much to them and easy to rebuild. Good luck. PS They're fairly heavy don't drop it on you!!
For the rear one look down on the inside of rear frame just a bit forward from the radiator. Should be bolted to the inside of the frame with four 1/2 or 5/8 bolts one line off the top that is a short steel "U" shaped pipe with a hose going down to the junction block on the rear axle where the lines to the wheel brakes connect. The line off the bottom goes forward from the bottom. The adjuster itself is about 5 inches diameter and 10-12 long(tall). It is kind of heavy as it has thick walls so might help to have someone hold on while removing the last bolt. Or a ratchet strap to hold it. If yo look at the picture I posted above it is pretty basic assembly. Just hold one half and unscrew the other. If you have a good work bench to work on you could bolt it down using the pads it mounts to the frame with and use a large chain wrench to turn the other end. An option for the chain wrench is to use a length of say 1/4 flat stock drilled with the pattern for the split flanges and bolt it on and use that for your wrench.