Hi Gents, Need some information on the brake system for my 988B. Symptoms- - Lazy movement like park brake still applied momentarily - brakes are just releasing if pulling pedal back manually - spool on valve moves only a small amount like it’s being stopped hydraulically - steering seems to cavatate here and there - oil leak on head of engine near gear pump What we have checked - accumulator is working - foot brake valve pulled apart and cleaned and sealed Then - plugged rear brake lines to get enough pressure to get this far I think I’m looking towards gear pump on back of motor that might be supplying this circuit can anyone show me a diagram ? Or have knowledge on this thanks.
G'Day & welcome Rick. First thing we're going to need is a Serial Number. I know there is a break either side of 50W7488 and that may affect the infromation on the brake system.
Hi Nige 50W05032
Attached the Specs, SysOp, and T&A for the brake system. I was wrong, the S/N break is at 50W6040, but you can see the reason behind asking. All the documents attached are applicable to 50W machines from first built to 6040.
Thank you Nige
Hi Nige got the machine mobile with your help. - Bled brake system - Found linkage seized between cable and brake spool valve (just oiled it) - Re sealed the tilt ram also. Main Ongoing issues is the machine needs the brake pedal pulled right back manually before gears will engage ! Any ideas? Thank you
I'm assuming that you mean the left pedal which also controls the transmission neutralizer, correct.? Is the right pedal also reluctant to come up after being pressed to the floor.? If yes then you should be looking at the linkages/pivots inside the red area on the brake control valve located on the RH side of the chassis behind the cab. You may even have to pull the brake valve (indicated blue) apart and free up the spools. There is no return spring on either of the pedals, everything relies on the guts of the valve being free to allow the springs inside it to push the cables back when either of the pedals are released.
Yes correct - left pedal needs pulling back Red area - was oiled and pivoting free now it was the main issue to start with Blue area - spool valve was pulled apart prior to oiling the red area funnily enough we went there first and is moving. I will have to check the spring tension on the spool valve again and maybe in the cab on the pedal linkage. I’m questioning the transmission neutraliser you mentioned Nige, is that the other spool valve on top of brake valve in the blue above, it’s called an inching pedal in forklift terms that circuit? Is there any way the button on the bucket tilt lever is connected? I know it has something to do with reducing power to driveline as well, I’m not sure if it’s even wired correctly but can see wiring from the lever down not sure where it goes ?
Have you lubricated the cable internally, or at least disconnected it at both ends and checked if they have free movement.? TBH if you do it for one cable I would do it for both. Regarding the operation of the transmission neutralizer you need the Power Train SysOp (attached). In respect of the button on top of the tilt lever I thought that was for the horn.? I'll dig out an electrical schematic and send it to you. Keep an eye on your messages. The variable torque converter control (if equipped, it was an option IIRC) is a 3rd lever mounted to the right of the bucket lift & tilt levers as per the photo.
Here’s a thought. Have you checked the brake accumulator precharge pressure.?
Forget what machine it was on but recall one where cable would move nice and easy if disconnected but would bind up when connected. Ended up replacing and then everything worked smooth. Disected the cable and found the inner cable had worn a groove in the outer housing and when any load was put on it it would wedge tight in the worn groove. Sometimes only fix is new parts!
Accumulator pressure is fine ended up being the cavitation oil from transmission suction line, small pin hole from a rubbing hydraulic hose ! Thankyou sir, it still needs more power though haha I’ll keep looking
Glad to hear you found the problem. I have seen the suction pipes get a hole in them before. One time had a 988 that was working fine but had to replace a bad hydraulic hose that had nothing to due with the transmission, but after it was replace machine would not move. Turned out the hose that had failed was laying on the suction pipe for the transmission pump and had worn a hole in it but was keeping the hole sealed. Installed new hose being careful of the routing to not have it rub on stuff but now the suction hose was sucking air! Once I figure out the problem removed suction pipe and brazed a patch on the hole and put machine back to work!
Yep that’s the one ,I couldn’t believe a tiny air hole could stop 45 tons of loader hahaha
Thankyou so much next inspection will be wiring to the torque converter to make sure I’m getting all the grunt to the ground ! It is lazy still !!
Hi Rick, Just wondering if you found out a fix for your loader to be "Lazy" still. Having a similar issue with mine S# 50w10420. I haven't seen the loader being used but the operators are saying its like it doesnt have power to climb out of small holes/soft ground. Possibly thinking it has something to do with the variable torque and curious if you found anything interesting with yours Thanks
Tbeau - try downloading all the attachments in Posts #4 & #9. Once you understand how the system works it might be easier to troubleshoot. If you need any more information regarding the VCTC operation just ask. TBH I seem to recall most customers simply locked the VCTC control at maximum and left it at that.
Thanks for the info Nige, I finally made it out to the machine and found out why they had issues.... they are overloading the front with large railcar boxes ( forks on the Cat 988 not bucket), so the back tires were off the ground. They managed to completely snap/rip the front drive shaft off and even took some of the frame material with it on the steady bearing assembly. So I guess with no front driveshaft they definitely would be having power issue.... just shake my head and roll my eyes. Of course operator has no idea what happened and the complete driveshaft, yoke and ujoints are no where to be found...almost like someone quickly disposed of the evidence. Gotta love renting out machinery to companies that have zero respect for the equipment.
And I hope that you invoice them in the same way for the repairs. Find every small thing that can possibly be related to the operational damage, fix it, and send them the bill for the whole shooting match. As a starting point replacement Cat drive shafts aren't cheap.....
I 100% agree with you Nige. I like to employ the “stupid tax” on these kinda repairs, the more stupid you’re gonna be…the more you gotta pay. As some added ammo if they bicker about the cost, I have a video of them driving just on just the front axle overloaded back in the spring when I first delivered it so they can’t say that it was missing when they got it or that they “don’t abuse it”.