Hi,help needed  I have a Transcrete P35 and it’s developed a slow stoking piston on one side, it gets worse the more pressure required, I’ve had rod seals replaced with no effect, any thoughts pls ???? pump is 12 years old 

Update for anyone experiencing same symptoms 

first had piston rod end seals replaced made no difference 

another mechanic removed all the cartridges form spools and found damaged and missing o rings, replaced them and now my baby pumps like new again ????

This is a common issue that could have several causes. Based on similar problems reported by other users, here are some potential solutions to check:

What's Been Tried

• You've already replaced the rod seals with no improvement - good troubleshooting step, but clearly not the issue here

Potential Solutions

1. Check the hydraulic cartridges/spools: A user with very similar symptoms on a Transcrete found that damaged and missing O-rings in the cartridges from spools were the culprit. Once replaced, the pump worked like new again.

2. Examine the hydraulic circuit:

   • Look for any internally-bleeding hydraulic motor or circuit
   • Check if there are valves that might be half-engaged (which could also cause heat)
   • Inspect the pressure relief valve to ensure it's not malfunctioning or sticking open

3. Logic valve components: Another possibility could be a broken spring or orifice/set screw in the logic valve

Testing Steps

• If you can engage the PTO in a high gear, does it kill the engine or pressure out? This could indicate issues with the logic valve.
• Check if any other hydraulic components on the same circuit are running at proper speed.

Since the issue gets worse with increased pressure, it strongly suggests a hydraulic control problem rather than a mechanical issue with the piston itself.