My hydraulic pump pressure seems to surge when the tractor is running at any speed. Replaced the hose from the pump to the controls as it started to bulge and then blew from the surges. Put a new hose connection on yesterday and the metal pipe at the bottom of the assembly rocks some from the surges now, worried the metal tube will eventually fatigue. Is my pressure relief valve sticking and causing a pressure build up? I can't find anything on rebuild kits for the valve. Is there a rebuild kit available or is there some particular parts that I should look at replacing in the valve? Tried doing a search in the farmall discussion forum but couldn't come up with any info.

Thanks for both replies. The surge problem has been going on for a couple years and sliowly getting worse. Just got the tractor back from the dealer after clutch and ta replacement and piston sleeves replaced, so has clean oil and filter. Sounds like I need to check the pressure releif valve parts. Hadn't read anything on pressure build up from the valve in the forum so wasn't sure if that happened or not. Will try my luck in a couple days when it warms up.

Concentrate on the orfice plug in the regulator valve assembly. It is the screw driver headed plug right in center with cover off. If it has never been replaced you will see a roll pin with a steel ball under the pin. That little ball bangs back and forth and closes off the orfice hole. Also, if it is a later ball and pin style, that seat will be hardened. They still peen them closed but makes it real hard for a tiny drill to clean them out.

New orfice screen assembly did not have the ball and pin. Hole originally is .031 and , like said, usually drill to about .040. Too big, won't go on pressure, too small will surge or stay on high pressure.

Also, you will no doubt find the screen on orfice assembly collapsed. You can clean that screen by cutting off the end, cleaning it and then just roll the end up a little to close it off. Good share of the time though, screen is damaged. New ones are MADE OF GOLD according to the price.

That cover has a very heavy spring on relief valve. Remove corner bolts of cover and install longer bolts to prevent problems taking cover off and do same to reinstall. Regulator valve piston has a 0-ring and also a orfice that you should blow out. It is also spring loaded and should not be rattling around inside.

The system is demand driven a pilot valve in the safety regulator block has both a screen and a orifice through it. if plugged or collapsed screen or plugged orifice, it will pulse. Max drill size on orifice is .040" Jim

More then likely your valve is having issues with sticking and this can be caused by something going out in the transmission or rear end and fine pieces of metal getting past the filter . Many years ago while still in the LEARNING stages of tractor repair i bought a rag 460 and started to fix it up . Learned a lot on that one . While plowing one spring the right inside axle bearing went out to lunch and made lots of vary fine filings . Yea ok so the bearing went out big deal just have to FIX it . SO not only did i replace the one but if that one was going south the other one may not be far behind . So both got changed . NOW what i should have done was not only replace them but every frigging bearing in the trans mission and rear end . BUT i did not just the two . We washed out the trans and rear best we could with mineral spirits then hot soapy water let drip dry blow dry then new hyd. filters as mine had the do nuts as it was and early one and brand new HY TRan (back then you could afford HY TRAN with out giving up your first born ) and put it back to plowing . Second day while plowing all of a sudden she lost power and stalled dead in her tracks . The pressure relief had locked on high pressure and plum killed the engine . . That took awhile to figure out .So we cleand and lightly polished the spool and cleanead everything and changed the hyd. filter and it was plugged full of filings and some got past the filter . And went back to work . About ten rounds later as i was coming up out of the furrow and making the turn she started loosen power again and plum stalled , so back in to the valve and it was STUCk from filings and the filter was plugged solid . So clean the valve new DO NUTS and back to work made a full day before she did it again . SO now we drain all the hyd. oil out drained every place we could put new DO NUTS in and filled her with Diesel fuel and drove her around the block about four miles of driving and drained her , changed filters again as i have now bought a case of do nuts and a dozen cover gakts and filed her up with diesel again after draining everything i could filled it back up with diesel again and around the block and drain and change . After the fourth time i figured i had her pretty clean and all was well while we were getting the crops in. So now it's time for some FUN and lets go tug the sled . Well off came the fast hitch and a H draw bar was installed weight brackets mounted governor by passed timing set up cab tricked out valves rest and off to the pull First class she come out the gate just storming down the track engine plum screaming and hauling the mail When the pressure relief locked closed and plum killed her dead on the track. and would not even let it turn over to restart . I fought with that tractor for two years and was never so happy to see something go . The new owner never had a problem with it other then the clutch sticking to the flywheel one years and i had to go fix it for him . SOO LOOK AT YOUR HYD FLUID and filter for fine metal filings and if ya find some word to the wise start looking deeper as to where they are coming from as i can tell you your in for FUN .

That sounds like a nightmare.. What's a good IH service manual for the hydraulics on the 4 and 560?

I went through my pressure relief valve a couple years ago. If you look it up in the parts book there isn't much in there but could be the valve is sticking. I changed the spring in mine and think there were some o rings not any way to adjust it.