I'm no Cat dozer expert. The boss brought in a D8L. He wanted me to check it out the other day, let machine run long enough to warm up while checking it out. I foot throttled down, engaged R1 to back out of slot, felt tranny engage, and motor loaded slightly, but didn't move. Had to throttle up to move. She started moving, I steered it to drive on lot. Foot throttled down and selected N, it came to an abrupt stop. Hmmm. Engaged F1, same thing as rev. Even when your changing speeds, you can feel it trying to stop during the lull of tranny changing speeds. If you are moving along in drive and were to hit N, it quickly comes to a stop. Just feels like the master brake is always applied. Moving brake pedal in and out seems to make no difference. Not at all familiar with these machines, what do I need to look for? Thanks
Atco, Try lifting the blade off the ground:drinkup
LoL...that's a good one Dave! :lmao :falldownlaugh I tip my hat to ya on that one. :wink2
D8L feels like brake is applied: ATCO, does a D8L have differential steer or track clutches/brakes? OCR
Always glad to be of help! OCR, I'm 99.6% sure the 8L's were clutch and brake.
You might wanna check the linkage on the park brake lever. It might not be letting the brake fully release. Pull the floor board out and check all the linkages under there, as well as coming down from the shift tower. On the L's and N's that didnt have diff steer the lever applied the service brakes for a park brake. They are not a seperate system. Hope that helps. If not, do as dieseldave says, but you might wanna pick up the ripper too!!:drinkup
D8L feels like brake is applied: ATCO, did you notice 3 big white marks on the shop floor, after you backed it out? OCR...
Yep, your advice is much appreciated. And on this occasion...much laughed at! OCR, I'm pretty certain they use hyd applied/released brakes and clutches to steer. But Cat dozers like this have a Master Brake pedal on the floor to apply brakes, like for when your holding the dozer on a grade. It just feels like this master brake is applied always.
Yep, that's the first thing I plan on doing JTL, removing the floor and start checking links. Never been in the innards of one of these, so beyond the obvious of checking links and bell cranks, a little clueless on this one.
I would try to get the Caterpillar service manual for that specific machine.
Two questions, as I am unfamiliar with these machines; 1) if it's clutch/brake steer, which I think it is, does the Master Brake pedal on the floor apply clutch brakes? Or does the Master Brake pedal on floor apply a different brake? 2) the safety lever. Does it apply a brake when the safety lever is down? And release that brake when lever is up? If so, which "brake" does it apply or release? I know...that's more than two questions. LoL Let's call it "two question categories". :yup
Thanks Buckethead. I will get the manual if it becomes necessary. Just thought I'd pick the brains of experienced wrenches here at HEF first and see what tills up.
The brake pedal on the floor applies the steering brakes on both sides at the same time, and does so with out much modulation. When you step on the pedal, they are there! There are a set of steering clutches and a set of steering brakes (both are disc/plate sets) on both sides. As you move the lever back, it first disengages the steering clutch by dropping the oil pressure that holds them tight. As the lever is moved past the halfway point further back, it starts engaging the brake until it locks up. The brakes are spring applied, so when the brakes are engaged, the oil pressure is being lowered. When the park brake is engaged, or you step on the pedal, the oil is simply dumped on both sides. As stated above, checking the linkage would be an excellent starting place.
Lonestar's post about the brakes being spring applied and realeased by oil pressure sparked something in my mind (and yes it takes quite a jolt:cool2). I worked on a powershift Cat years ago that had brake release problems and if I remember right the pump wasn't making enough pressure to release them. Also, if you move the machine and pull each clutch lever a little bit- far enough to release the clutch but not far enough to apply the brake- you should be able to feel if it's one side or the other hanging up, or both.
Thanks for the operation description LonestarCobra, that's what I needed to know. :wink2
Had a similar problem on a 8n once, ended up taking tranny out and finding the pipe that keeps the brake of had cracked therefore wouldn't maintain pressure to keep the brake of which was a fault on some of those 8's. The new pipe had extra mounting brackets on to prevent it vibrating and cracking again.
As I recall the L series dozers were all clutch and brake systems as the diff steering had not been invented yet. The transmission safety lever is interlocked with the parking brake system. As I recall those machines had standard quick couplers already installed to check pressures. If the linkages check out that is your next step. Some of the transmission check points were on the back of the machine. As I recall the steering check points are under the seat. You should be able to see the couplers easy enought when you get the sheet metal up. However knowing which tin to pull is beyond this old and feeble memory. Good Luck!
A couple times after our D10N set for a couple months the pin on the transmission lockout lever seized and wouldn't let the brake release. It took a 10" cresent to work the rod back and forth while spraying it with Zep 45. Which is kind of like WD 40, if you're not familiar with Zep. I'd check to make sure it has full travel. Real quick fix if it is. You have to pull the floor board and crawl down inside to get to it.
Seized Cartridge in the Solenoid that controls the Park Brake Pressure.Mounted in the Bottom Sandwich of the SCAB Valve........................???
Seized Cartridge in the Solenoid that controls the Park Brake Pressure.Mounted in the Bottom Sandwich of the SCAB Valve........................???
Wow!!!I found somebody else that uses Zep 45!!I would not be without it. For what it is worth the older Cats,D6/7/8 all had a rinkydink system for applying the park brake as you could not count on it to release completely when you wanted to release it.More than one employer cautioned me on it and it was always on my mind,kind of like the PTO in a dumptruck,ya know? I have no reason to believe that there would not be some changes made with a later model machine but it is always in the back of my mind.Ron G
Just try pulling the brake pedal back up towards you and see what happens, the brakes may well be just doing as they are told ie pedal sagging down a bit so brakes are on slightly. Pedals return spring may be weak. Pressure checks will also help verify this. Brake is the second half of the steering levers movement as the steering clutch is disengaged in the first half movement and usually if the bevel springs in the brake portion are a bit tired it is hard to get them to turn when and how you want.
atco should check implement pump pressure....if pump requires replacing,better crack open piggy bank. If you recall I just had to buy one. They run about 5500 bucks. I hope it just adjustments.
Thanks to all, a lot of great advice, I now have some direction to approach this critter. :notworthy Yes, Gavin, I did think to check that brake pedal was operating properly and coming back up fully. Next thing is to pull metal and start checking components. With a little New Years luck, maybe it will be a simple fix.
LonestarCobra gave a very nice explanation of how the brakes work on this machine and linkage is the smart place to start in order to make sure you are getting full stroke to the control valve which allows oil pressure needed to overcome the Bellville springs and release the brakes. The only concern I have is that this machine has a priority valve that is not supposed to allow the transmission to engage if brake pressure is too low (320PSI). Since your transmission is engaging this means that your brakes could already be burnt up and warped from the heat generated from operating through them (it doesn’t take long) and if so you will have to pull them out for rebuild. One trick you can try if the machine has a ripper is to get the tracks off the ground and put it in gear at low RPM to observe if both tracks are dragging equally. It is unlikely that both brakes are damaged but if they are this could be an indication of another bigger problem that led to this problem. We have all the books, advice and components you need if we can help. By the way, there is a serial number break on the D8L that dramatically changes the steering system so we will need that in order to go deeper into troubleshooting and repair.
The boss finally let me tinker with the 8L. First thing to do, remove the floor plate. Haven't worked on an 8L before...geeez, there's a basement under the floor plate! Climbed down in the hole crouched on top of torque housing, started checking things. Noticed immediately the brake linkage wasn't allowing control arm to fully return. Pulled the linkage bolt connecting to arm on control valve, arm popped back. Problem, siezed bellcrank, rip the assembly out. Very common problem on dozers and loaders that have linkages controlling valves. Over time, the grease in the bellcrank levers dries up or is contaminted by dirt/dust. The needle bearings begin metal to metal wear against shaft. Small grooves begin to form on shaft. Metal dust and rust begin to build. Next thing you know, the bellcrank arm will not turn on the shaft. Don't even waste your time trying to apply spray lube to get them to free up. The bearings have small lip seals on them that prevents entrance of spray lube. Besides, when they start getting siezed, the needle bearings and shaft are done anyway, time to rebuild the bellcrank. :yup Spotted an o-ring boss plug leaking while I was in the cellar, easy enough to fix that. Took plug out, o-ring was hard as a brick from heat. I'd say I better check some fitting seals. Also saw the transmission charge pump is leaking. Going to have to take it apart and see what kind of shape it's in.
Cat had that same problem on the D8K and 9H dozers I worked on. They did away with the brass bushings on the old H models and put these crappy bearings in with no hope of lubrication. I cussed a lot of engineers and bean counters in those days. Nice job of troubleshooting and repair. Also thanks for the photos. It's nice to see someone actually crawl into the hole and fix a problem before a catastrophic failure. You provided a a real good example of how to process the complaint and repair it.
Thanks John C. Yep, sure was different being able to work in such an open area underneath cab. Heck, on smaller dozers, you have to stand on your head and work on things that are crammed in a small package, this beast ain't bad at all. Just thought I'd post these pics for others who have sticky links to see. Like me, I'm sure you've seen your share of siezed joints on Cat as well as Komatsu machines, and to tell them don't even waste your time trying to lube them, take it apart and fix it. Spotted a couple of leaks while in there, gotta get them sorted out, then clean the nasty thing.
That looks real good ATCO! Nice to see someone fixing things correctly. Just remember>A good mechanic isn't expensive, he's priceless!
A little TLC goes a long ways on older machines, makes you feel good to fix something simple like that. Time well spent
While you're fixing the bearings, drill grease holes in the side of the bellcranks and screw in grease zerks....never be a problem again if you grease it every year or two.
Be kinda hard to do that on these D6c10K. You could put grease zerks in the bellcranks, but the bearings don't have holes in the side of them to allow entrance of grease. Got the parts today. New shaft and 6 bearings. Got everything reassembled, reinstalled the bellcrank assembly. There's another bellcrank just prior to this one, it was working ok, but, I'm in here. Knocked the shaft out of it, cleaned it up, greased bearings, fit shaft back in place. Now everything is happy as a clam. Hopefully, I'll get a chance to go into the leaking tranny charge pump before someone comes along a purchases the machine. I'd like to get pics of that repair and post them for all you guys to look at.
Atco, Where the bellcrank has 2 needle bearings, you put the grease hole between the bearings so the grease feeds from the center, through the bearings to the outer ends...at least that's what I did in several places on my linkage. (brake pedal pivots, trans shift linkage etc) All depends how accessable it is for greasing too.
Ok, that makes sense. All one would have to do is trim out the lip seal on the inboard side of the two bearings, then grease would flow into the bearings. Might have to try that one day. :cool2