8N Hydraulics - will not lift after mowing with bush hog (2024)

I have a 1952 8N. While running in neutral, hydraulics work fairly quickly and smoothly with bush hog attached. I can raise and lower the bush hog without any problem. Pump seems strong. After 30 minutes with bush hog raised, the bush hog will drift down a couple inches. However, while mowing with bush hog down, it will not raise up immediately, I have to wait about 5 minutes for it to raise. Took the right inspection plate off. There was no indication of oil leaking out of the ram cylinder. Anybody have any ideas, thanks.

Does it have the correct hydraulic oil? I don't know about Fords but on my Farmall H where 30 wt oil is the recommendation a lighter oil like hydraulic oil will get hot enough with a lot of use to not lift properly. How about a filter in your system needing cleaning? Just a couple of ideas. I don't know what the source of oil is for your system - separate oil or shared with rear end oil.

So..........your problem seems to be heat related. Is your oil too thin? Warmer oil is thinner and can squeek past worn hydraulic components.

oil was cleaned, had no water and a couple of spoonfuls of sludge. I replaced it with Napa mineral oil. works the same

Supposedly the Napa mineral oil 90W is one of the oils to use. heat is a good point. 1. I read numerous posts on type of oil to use, unfortunately, people recommended a wide range of oils from GL1 to GL5. What I can gather is the oil has to be compatible with the type of metal used which is yellow metal, I believe. Having said that, what oil can i use that would be thicker. also, would the ram cylinder be leaking, due to the thinness of oil?

Ram leaking generally results in the load drifting, then recovering. Hick-upping. Would also see a fair amount of oil leaking past the piston. I suspect you have a pressure problem. Might take this discussion to the 8N forum for access to folks more knowledgable in 8Ns than I. Best of luck !

I googled NAPA mineral oil. Many different possibilities come up. Try posting the exact name again. Regular mineral oil is way too thin to work when hot. Your 8N's pump is likely worn and probably needs a heavy oil to work when hot.

Napa Sae 90W Mineral Gear Oil, API GL1

Is it part# 65-0205 in 5 gallon container?
That is correct oil for 8N.

Part #:NHF 65205, The oil is known to be thin. Assuming something is worn, i was going to ask part stores if there is a GL1 gear oil that is heavier. The operation isn't that complicated. When the bush hog is down, the pump idles. the ram cylinder goes all the way forward. When the lifter is moved back to raise the bush hog, the valve opens allowing fluid in the pump which pumps into the ram raising the bush hog. I am not experienced with this equipment to determine what the symptoms of one over the other. The things that could be an issue is the pump cylinder, ram or relief valve. I have seen in other equipment that a defective valve can open a little when no pressure for a time and once pressure increases it closes. I have not read any where what the symptoms of a faulty relief valve in this pump are.

IMO your oil should be fine. My guess is your pump is not making pressure when hot. If symptoms were the same cold I would look at relief valve.
Some one else may have some good ideas. Try adding 5-6 bottles of STP oil treatment viscosity enhancer. I know it raises oil pressure in my Ford.