2001 Cat 303.5 CAT03035KDCH60980 Bought this as a project, previous owner ordered a Chinese pump but didn’t get around to putting it on. I put it on along with all fresh fluids and filters, everything works as it’s supposed to except I have a couple weak functions. The swing and the blade. I have the manual and have been checking pressures but still not figuring it out. Following the test swing procedure in the book my swing is taking 24 seconds for a complete SINGLE rotation when it’s calling for 3 rotations in 18.8 seconds. 1. Following the pressures in the manual I’m only getting 2100 out of the P3 pressure port when putting the boom against something solid, it says to adjust relief valve till it’s 2550 but it doesn’t tell me which one to adjust, any idea? 2. I tested the blade at the P3 pressure port and I’m getting the correct 2700 psi it calls for when holding the raise position. 3. I tested the pilot manifold at the pilot manifold port and I’m getting the 475 PSI it calls for. Any help will be appreciated it
Slow swing but correct blade pressure at the same P3 port is your key clue - this points to swing motor or swing-specific valving, not the pump. Here's what's happening: P3 pressure low (2100 vs 2550 psi) under boom load: You need to adjust the main relief valve for P3 circuit - it's typically on the main control valve block, labeled or color-coded for that section. Check manual schematic for exact location. Adjusting this will help overall P3 performance. Blade gets correct 2700 psi but swing doesn't: This means P3 pump section can make pressure, but swing motor has internal leakage or the swing counterbalance/brake valve is malfunctioning - restricting flow or bleeding off pressure. Pilot pressure good (475 psi): Rules out pilot system - swing spool is getting commanded properly. See: Swing motor case drain flow: Disconnect and measure - high flow = worn motor seals Swing brake valve: Check if it's releasing fully - partial engagement causes drag and heat Swing spool/valve: Could have restriction or worn metering edges specific to swing That Chinese pump may be fine for other functions but could have slightly different P3 flow characteristics. However, 24 seconds for one rotation vs spec of 3 rotations in 18.8 seconds = you're at ~7% of normal speed - that's massive internal leakage in the swing motor. Test that swing motor case drain - it's likely dumping all your flow.
There are several things that can cause slow swing rotation and/or slow function movement. Regardless of what was said above, there is a check that is easy to do that may steer you in the right direction. Remove both main flow hoses at the swing motor and plug them.....1 or both with a 5000 psi gauge. Engage your swing and see if you can get to relief pressure. If you do, then your pump is capable of building the pressure needed, you have a flow problem. Just because you have the correct pilot pressure doesn't mean you have enough movement in the main control spool for the swing section. I would then check the pilot hoses on the swing section for the proper pressure AT the spool itself. If you have that pressure there, you need to make sure you have full movement of the main swing spool. There are numerous places in that circuit that can be the source of pressure/ flow loss. There are other checks after these that can be done to get to exactly where the problem is. Don't start throwing expensive parts at this and definitely don't make assumptions.