Came across this post due to same issue with my older 4200. Based on what I’ve read, I’m not surprised that the dealer didn’t find the original fitting the screen came from but it’s there. It is at the far left end of the hydraulic line under the plastic cover the handbrake lever comes through in your picture in the last coupler fitting the hydraulic line attaches too, not in the line itself. The line that runs behind the seat makes a 90 degree turn and runs towards the front of the tractor right after it disappears under the plastic cover you didn’t remove on the left side in your pictures. It looks just like the couplers used elsewhere in the system except I think it is a little longer. The screen is somehow pressed in and can’t be replaced. This coupling with screen has been replaced with the standard coupler in later tractors that have the filter screen mounted in the middle of the line behind the seat where the white x is in the marked up pictures after your initial post. Anyway, this thread was helpful for me because I’m hunting hydraulic issues and found that my screen in the old style setup was broken/pierced. Based on the information in this thread, there are most likely fragments of the screen somewhere upstream in a control valve. Since the dealer said they didn’t know anything about your original old style screw filter, you may want them to go back and remove the old coupler that had the screen because in mine it left residual metal strands that could still break free after I removed the first main screen fragment. There is no screen downstream of the faulty screen to catch these. The new filter screen setup, if you’ve had it installed, is upstream and won’t help if any more metal comes loose.
