I just purchased a 980B (I believe 1972/1973). I’m going to be moving it this week so I stopped in today to check everything and make sure it’s ready to go. The air brakes aren’t releasing fully. They were working a couple months ago when I first checked out the machine. Anyone have some insights on things I should first check? Stuck linkage maybe? I’ll be stopping back by later today to work on it and will get the serial number if it’ll help. There is also some minor air line leaks I will be going through and fixing once it’s at my shop. Thanks for any help!
Well can't be 100% sure without the full S/N but I'm thinking all the 980B's used the same what I call straight air brakes. One slight difference being there are two brake chambers for each front wheel, two per camshaft! One possible thing to check would be to make sure you can build up full air pressure 120 psi. Then release the brakes and maybe use down pressure to lift the front wheels off the ground so you can try turning them by hand to see if drag is in the front. Lots of things I might check if there but might be hard to mention all them and would not want to leave out something that may cause one to be at risk. I'm attaching a Systems Operation on the air and brake system to give you an idea of how the system is set up. If they are releasing enough to let you load and unload machine and get it to your shop I might be temped to just wait till it is a a better.safe place to work so you can have tools and things like wheel chocks to make working safer.
A quick look found these manuals available: https://www.servicemanualpro.com/?page=products&category=28&model=980B WHEEL LOADER There are others but that will give you an idea.
Give a yank up on both brake pedals. Sometimes they can get sticky if not used for a while.
Good one I should have mentioned that! I "lost" a transmission rebuild job in a Cat loader once because I did just that! Really did not want to take on the job and was glad to tell the owner the real problem. Fixed it in 2 minutes with a squirt or two of penetrating oil and working the peddles up and down!
Did he give you a bonus for fixing it fast and cheap
Serial is 89P2953. When I first got there I tried to pull back in the brake pedals and one was slightly stuck half way. My initial thought was “yes! It’s gonna be an easy fix.” I wasn’t so fortunate. Still stuck brakes. here’s a picture of the front brakes. Appears there’s an issue. Any thoughts?
Also I notice when the parking brake is set the air pressure rises decently and when it’s off it builds much slower. I mention in case it’s a clue. I’m not familiar with this machine and brakes so any advice is greatly appreicated.
The park brake chamber may be leaking air. If your air pressure gets too low it will start applying the park brake when you are trying to move.
Keep in mind just because you pulled up the pedal it is not guaranteed that the plunger in the brake valve under the peedle came up also.
From the picture I posted it looks like the rod is stuck up. I assume it should be pushing back down against the nut/washer of the bolt. I don’t know exactly how it works on the other side of the housing.
How would you go about troubleshooting to see if this is the case? The pressure shows to be in the green when the brake is off.
The picture in the photo indicates to me that the maxi cans are applied. The chrome should be all the way back into the chambers.
Any ideas on what would cause that? Big hammer them back in (haha)?
Well, a big hammer might release them if the cam they are mounted to is stuck in the bushing going into the wheel or the return springs in both brake cams are broken. I would take an air line off the feeds the cans just to see if releasing the park valve actually is sending air down to the cans. At least this will tell you which direction to look.
Tthis is one of those times where not being there can cause hours of work trying to trouble shoot something that might take five minutes if there in person. First thing I would say is make sure you have this machine blocked so it an not roll and kill you, we don't want to have to explain this to the next owner, if you get my drift! Now my first question is: When that picture was taken was the air pressure up full and the parking brake button pushed in? That chrome sleeve should be all the way in when parking brake is released. Maybe 1/8 inch exposed at the most. They look to be sticking out close to 2 inches. Why the right one is right against the flange nut and the left one has a big gap indicates there is a problem in one or both those brake chambers. Take a look at this drawing from the information I posted in post #2: When you release the parking brakes air pressure goes into the port with the red arrow pointing to it and moves the piston labeled #4. This piston is attached to that chrome tube you see sticking out. The air pressure pushes the piston up and compresses the spring marked #13 and this releases the brake. The chamber in the drawing is showing the chamber in the parking brake released mode. As you can tell there is almost none of that chrome tube sticking out the end of the chamber. The port with the green arrow is where the air goes in to apply the service brakes. One big word of caution is if you even think about removing and taking one of these chambers apart unless you have worked on them before and fully understand them do not even think about removing the bolts marked #6 in the drawing. That spring marked #13 could be said to have a very appropriate number #13 as it can be very bad luck if it is allowed to be let loose! We don't want the next post here to be from next of kin! I would be interested in knowing how all the other brake chambers on the machine look in regards of those chrome tubes when machine has full air pressure and the parking brake button is pushed in. They should all be back in like the one in the drawing shows. Again just to be sure you read it before make very sure the machine is blocked so it can not move before getting near it with brakes released. DO NOT trust the bucket to hold it from moving! This machine has one of the simplest to understand brake systems but also can be a major problem if one does not take the time to understand the basics. If I was located a half hour drive away I would run over and give you a hand this morning, but being on Central NY that's not going to happen! There are things I might do if there that I would hesitate to even hint at to someone via this forum or by email for fear that what I say might be misunderstood or not followed to the letter.
Excellent response. I wasn’t able to get back over to the loader to work on it today. Hopefully I’ll have a chance tomorrow. The picture was taken after I had shut the unit down and the parking brake was set. I’ll get a picture of them with the parking brake released and see the difference. Also I noted the rear brakes move very little with the service brakes applied and also when parking brake is set. Perhaps 1/4 inch. I’m attaching a photo of the other side with the parking brake on. You can see one of the two chrome sleeves also is not all the way down on the flanged nut. Wheels chocked and I know not to take air brakes apart without proper tooling. I appreciate your comments and concerns and know how serious they can. I ordered the correct service, operation and parts manuals for it. They’ll likely be here Monday. Until then I’ll see what the brakes do when the parking brake is released. The brakes seemed to work fine when I looked at the loader a couple months ago and it hasn’t been used since. Hopefully it won’t be too much issue to get them back to working so I can get it moved.
Some of the difference in the amount of chrome sticking out or the clearance between the chrome and the flanged nut is probably due to the adjustment of the slack adjusters. Attaching the adjustment specs on the chance you have time before manuals get there: It does not spell it out but I'm sure you understand that the parking brake needs to be fully released(chrome pulled all the way in the chamber) then have someone operate the foot brakes while you measure the extension of the rod the slack is attached to. And that the 2 inch spec. is the maximum before adjusting. A rough setting to get them working might be to adjust tight then back off the adjuster screw around 1/4 to 1/2 turn. Then if they are working I'd run machine around a bit working the brakes to polish drums and brake cams then get fussy!
I was able to get back under the loader today and work on the brakes. I got 3 of the wheels/brakes to free up. The fourth (left front) has an issue. I ended up putting a jack on one and it will move the linkage. The brake releases however it won’t hold pressure enough to release on its own. I removed the clevis pin and the other one functions somewhat normal. I believe when I get it to the shop I will be going through each one. Brakes are something I want running perfect. I assume they make kits for these or parts are available? I’m looking forward to having the manuals so I can see the parts breakdown. Picture is of the right side with the parking brake released. The outer one on the right side doesn’t want to move very much and I believe is leaking a bit of air.
Did you know that you can download a pdf Parts Manual from Cat for about $90 and have it immediately available..? I can walk you through the process if you're interested.
I'd take a spray bottle like window cleaner comes in and mix a little dish soap with water and spray around the chrome shaft to see if air is coming out. There should be none when brakes are released! And chrome should be sucked all the way back in and stay there till you apply the parking brakes!
I definitely have two that are leaking as I can hear them. I’ve got a lowboy coming tomorrow to haul it home since it moves good enough to get on a trailer. Then I’ll be going through them one by one and getting the brakes in good order. I received the service manual and parts book which are quite helpful. I also have a few leaking seals on the machine to repair. Overall it’s a nice loader in good condition.
Does look pretty good in that picture, still has the ladder on the left side! At least you have the "B" and not the original 980! The original 980 had about the most complicated V-8 diesel ever built, I actually liked working on them but they had way too many parts and cost a ton to rebuild, timing gears and balance weights up both ends of the engine! Feel free to ask for advice here or by private messaging.