Serial number 11258. customer complaint of having to rev the engine to get any hydraulic function and the brake pedal pulses when depressed. Pumps are supposedly 3 years old with low hours. Hydraulics work correctly otherwise. Don’t have any experience with this machine and don’t have a manual. Does anyone have any info on checking pressures and any experience with the pulsating brake pedal? Thanks
Any pressure checks?
Well my first thought is always to check pressures but I don’t have a manual or a procedure. That’s the info I’m looking for. Setting pressures may correct all his issues.
I'm thinking that is a pretty old machine and the brakes shouldn't be too complicated. Should be a gear pump with the pedals attached to regulator valves. All the older loaders that I worked on had internal wet disk brakes. I don't recall there even being any accumulators in the systems. The easy stuff to check is dirt under the peddles, hydraulic level and return filters. Axle oil levels and if they had changed it recently. All the wet disk brakes in those days needed tractor hydraulic oil for the axles or a friction modifier added to engine oil in the axles.
I got over to the machine this morning with the procedure to check pressures. Spec is 3000 psi on the tilt circuit at high idle. I had around 2500 and the longer I held it on relief the more it dropped. I tried adjusting the main relief. I ended up turning it in 3 full turns and got zero increase in pressure. I spoke with the service manager and he didn’t have any answers besides that a new relief is cheaper to try than a new pump. Besides having to rev up engine to get hydraulics to work it really doesn’t have a performance issue. It still seems to dig fine. I’m thinking I may try a new relief before I condemn the pumps and I’m going to get this issue fixed before I chase the brake issue because the brake issue came after the hydraulic issue so I’m thinking they’re related somehow.
I don't know about that size machine but the bigger machines used a switch pump that was prioritized to steering and brakes and the excess flow went back to the loader hydraulics. If you follow the tubing and hoses from each pump, you can probably figure out if the system has that or not, if there is enough room to trace that is. When I worked on Komatsu loaders all those years ago the pump on them were aluminum bodied pumps and your problem sounds about what we always ran into when the pumps went bad. You can pull the reliefs apart to check the cone for a ring worn into it. If you can't feel the ring with you finger, it's likely not your problem. How many hours are on this beast?
Unknown hours but I’m sure it’s a metric s#$*load with not a lot of maintenance. Supposedly the pumps were replaced 3-4 years ago. (Not that it means anything) Oil is slightly milky but I’ve seen way worse. Return filter in tank is free of metal. It could very well be the pumps though. I’ll swing back and remove the relief and inspect for a ring
Stopped back by and pulled the relief out. Here is what I found. Of course komatsu doesn’t have one and the lead time is 60+ days.
Looks like they have been running sand in the system. How deep is that groove? You might be able to buy some time by polishing that on a lathe and putting it back in. As bad as that piston looks, what are the chances that the pumps are any better?
That’s a good point. I’ll bet if I removed the pumps and disassembled them, they would look similar to the relief
Pls check the brake master