Please help, we have a Cat 988H loader with a bucket tilt circuit problems. When pushing the bucket to pick a load the bucket is tilting back without touching the tilt lever. I am not sure what to check at this stage
If the bucket is out of the pile and you operate the tilt control does the bucket appear to tilt forward and back normally from one stop to the other..? If the answer is yes then my suggestion would be to tilt the bucket all the way back and push it hard against the rock pile so that it can't tilt on its own. Then remove the hydraulic line that supplies oil to the barrel end of the tilt cylinder. Start the machine and with the engine at idle move the tilt control to the "tilt back" position. If oil pi$$es out of the cylinder where you removed the hydraulic line then the piston seals of the tilt cylinder are fcuked..........
Thank you very much Nige, I will try that tomorrow morning. Yes the other functions are working good. It’s only when I am pushing the stockpile trying to pick a load when the bucket is tilting back before I use the tilt lever. I will try tomorrow this test you have suggested and I will let you know the outcome. Thank you very much.
The fact that you say the tilt function appears to go back & forth normally when the bucket is out of the pile would suggest that the control valve is likely working OK. So I'd stick with my original suggestion and go with pulling a hose off the tilt cylinder then operate the function to test the piston seals. Be careful that you remove the correct hose though or you'll get an oil bath .........!!
Hi, a serial number please or at least a prefix, there are a couple of different tilt/dump circuits on these machines the early one is quite simple and I would suggest swapping over the line reliefs to see if that makes a difference, the later models use tilt cylinder regeneration valves and dual line relief controlled by the ECM and are a bit different to troubleshoot Mark
I think the tilt cylinder is bypassing as you mentioned earlier. I tilted back the bucket and jammed it against a hard stock pile, switched off the engine. I disconnected the oil line on the barrel end / head end of the cylinder. I blanked off the steel pipe from the control valve.I started the machine and pulled the tilt lever at idling speed.Oil pissed out of the disconnected hose and stopped.I tilted forward a bit and back again and oil pissed out of the same hose again.
Sorry Mark 250, the serial number for this machine is LBXY02029.Thank you.
Thank you all, just waiting for a reman cylinder and will let you know of the outcome.
Thank you all for your contributions, it turned out to be the tilt cylinder line relief valve in the main hydraulic control valve,changed this and fixed the problem
-This type of event is not at all my forte so I read all these with interest....the last one I heard of that did similar curious things was also a faulty or low popoff relief valve...in the control valve. Do you think the cylinder behavior was an observation of a relief valve on that cylinder's piston? Some hydraulic diagrams show relief valves on the piston is why I am inquiring if you know this is the explanation of the action when the line was disconnected. I aim to keep collecting fittings so if necessary I can stick a tee with a gage in the system to help me figure this stuff out cuz it seems like the longer one does this, the more exposed to oddities.