Recently purchased a rebuilt PC50UU-1. Was a little skeptical of the rebuild, the exterior looks like it’s right off the showroom floor, the internals I’m still verifying. Did a compression test on the engine, came up with 425, 345 & 380, a deviation of 22%, highest to lowest. It’s my understanding that any deviation over 10%, is indicative of an internal issue, did I mention it would blow the oil cap off, just from cranking it. I do think the cap is worn and doesn’t fit as snug as it should, but I do believe blow back is occurring. Checking the hydraulic pressure next, first need to purchase a gauge that goes to at least 4000 psi and figure out how best to test it.
You could have some bad valves in head, but heavy blowbye is indicative of cylinder in bad state. how many hours on unit. Injector that is fueling bad will wipe out a cylinder. If you pull out glow plugs if it has, and shoot in some transmission oil with a skinny hose on top of pistons, the compression will rise greatly if the cylinders are the cause. I get a 3/16 OD hose 10 feet long and fill with oil and then blast a portion on top of a cylinder. I did a waterpump on one of these 8 years back but thats all I've done to them. Simon C
I had that same machine and sold it to buy a Kubota U45. I miss that machine everyday. I cannot even begin to tell you how strong those machines are or how nice it is having the setback boom for stability and loading into taller trucks.
Do you know if yours has a switch for the controls ? Mine has a sticker in the window showing A and B patterns.