Hello, I'm looking for help on my E70B excavator. I have a weird hydraulic issue where when the machine is warm, the right track and the boom are weak. They will move until they are under load and they will stop. After putting the gauges on the pump I realized that the pump closes to the motor must run those 2 functions. If I watch the gauge, it starts to build pressure and the abruptly drops to 0 when under load. The other side of the pump functions correctly, builds pressure and will hold it. Has anyone else had this issue? Supposedly before I bought this machine the main pump was replaced with a reman. Any help would be great and thanks in advance!
Is this a new issue that just came about or is it on its had awhile
It’s had it since I bought it. I’ve only put about 50 hours on it.
I'm not very familiar with how the pumps work on excavators. How does the main pump get its signal to build pressure? It must use the pilot system to tell it to build pressure? Any help would be much appreciated.
Post a Serial Number. I'll see if I can run down the System Operation document for the implement hydraulic system.
The machine serial # is 7YF06201. The main pump is an Rexroth A10VD43SR1RS5-993-5. I appreciate your help.
OK, so we are immediately up against a problem. Your S/N is a grey market import that was only ever designed for sale in the Japanese home market, not for export. So if there is any original 7YF-prefix service information out there it is likely to only be available in Japanese. Can you post a photo of the S/N plate please.? There is something I'd like to check. Here are a few Caterpillar Publication references that might help you. Original Parts Manual (Japanese) - XJBP9938. Parts Manual (English - reference only) - XEBP9966 Operation & Maintenance Manual (English) - XEBU9645 Service Manual (English) - SENR4570. Here is one on eBay at about half new price. NOTE: XEBP9966, XEBU9645, & SENR4570 are all for a World-market E70B excavator with a Serial Number prefix of 5TG. So based on that here are the SysOp and Test&Adjust documents for that model. I hope they are either the same or close enough to work on yours.
I appreciate the help Nige. I call cat again today to try to get some more ideas too.
I see in the operating system schematic that there are 2 check valves, one for each half of the pump. Could one of those be failing and causing it to lose pressure?