cdsl810 181 #1 Posted August 31, 2015 I have a new issue with one of my 520-H tractors. The speed is the same in forward and reverse. The hydro feels strong as an ox, and does not lose any power when warm. I have checked the motion lever linkage and neutral eccentric fitting--everything seems fine there. I am suspecting maybe a stuck check valve. Is there a way to flush the system and free a stuck valve? The oil and filter have been changed regularly and the oil is full and looks new. Share this post Link to post Share on other sites
WNYPCRepair 1,875 #2 Posted August 31, 2015 Not that I have an answer, but for clarity, is it running slower than it should forward, or faster than it should in reverse? Share this post Link to post Share on other sites
cdsl810 181 #3 Posted August 31, 2015 Normal in reverse, too slow forward Share this post Link to post Share on other sites
WNYPCRepair 1,875 #4 Posted August 31, 2015 Is your brake return spring good? Mine was missing, and it would feel like a manual trans in low range, couldn't get it to go full speed. Finally figured out if I pulled up on the pedal, it would operate normally. It's a shot in the dark, but, it's easy to check, too. 1 Share this post Link to post Share on other sites
cdsl810 181 #5 Posted September 3, 2015 The brake return spring is there and functioning properly.I have a hunch that there is just a stuck or dirty valve. So I drained the hydro oil and re-filled with some high detergent Castrol GTX 10W-30. I used the tractor for a couple hours and the forward speed is steadily getting faster. It is now at about 2/3 the expected speed--up from about 1/3. I'm going to run this oil in the trans for about 10 hours and then drain it and put a fresh filter on with Mobil 1. Whatever is causing the problem seems to be freeing up / cleaning out.I hesitate to actually flush a hydro with anything other than clean oil. 1 Share this post Link to post Share on other sites
bds1984 1,382 #6 Posted September 3, 2015 I had a similar issue with a Craftsman hydro. I've used 5W40 or 10W30 diesel oil warmed up slightly to thin it out to aid in flushing out anything that could be sticking. It took three flushes to clean it out the last one and it seemed to have worked. 1 Share this post Link to post Share on other sites
cdsl810 181 #7 Posted September 4, 2015 I just found some old shop notes of mine. Apparently I had a similar issue with the last 520-H I bought a few years ago. I used Seafoam Trans-Tune in that to clean it out, and according to my notes it worked great.I have young children. The sleep deprivation must have killed my memory. I'll post how everything turns out... 1 Share this post Link to post Share on other sites
WNYPCRepair 1,875 #8 Posted September 4, 2015 The brake return spring is there and functioning properly.I have a hunch that there is just a stuck or dirty valve. So I drained the hydro oil and re-filled with some high detergent Castrol GTX 10W-30. I used the tractor for a couple hours and the forward speed is steadily getting faster. It is now at about 2/3 the expected speed--up from about 1/3. I'm going to run this oil in the trans for about 10 hours and then drain it and put a fresh filter on with Mobil 1. Whatever is causing the problem seems to be freeing up / cleaning out.I hesitate to actually flush a hydro with anything other than clean oil. I was hoping it was something simple. Hopefully flushing it will clear it out. Share this post Link to post Share on other sites
cdsl810 181 #9 Posted September 9, 2015 I added the Seafoam Trans-Tune and let it run for a mowing session. The forward speed is now what I would consider "normal" for the 520-H. Whatever was sticking is back to normal. I did find a loose fitting on the lift cylinder that may have been letting air into the system as well. Everything is tight and runs great. Time for that hydro oil change and new filter. 3 Share this post Link to post Share on other sites
DennisThornton 4,769 #10 Posted September 9, 2015 Hope I never need to use it but darned good to know that it worked for you! Been pouring SeaFoam for years! Share this post Link to post Share on other sites
WNYPCRepair 1,875 #11 Posted September 9, 2015 Woo Hoo! 1 Share this post Link to post Share on other sites
JERSEYHAWG / Glenn 4,487 #12 Posted September 9, 2015 I have a new issue with one of my 520-H tractors. The speed is the same in forward and reverse. The hydro feels strong as an ox, and does not lose any power when warm. I have checked the motion lever linkage and neutral eccentric fitting--everything seems fine there. I am suspecting maybe a stuck check valve. Is there a way to flush the system and free a stuck valve? The oil and filter have been changed regularly and the oil is full and looks new. also, check under those linkages, someone posted they build up with crud underneath, mostly grass clippings and such. Keeps the free travel bogged down a bit. Take a peek, you might be suprised what you find. Just a thought.Glenn Share this post Link to post Share on other sites
