I have an old IH 574. Not a back hoe but I have a question that probably applies to lots of machines. When first started the steering and hyd lift perform as they should. After about a 15 minute warm up the steering becomes erratic and the lift only works at high engine rpm. Yes I know it is probably worn out. The question is- is there a thicker hyd oil that will "cure" things for a while longer? Old Uncle Dave
Has you changed hydraulic filter? http://www.tractorbynet.com/forums/hydraulics/206741-ih-574-hydraulic-filter-location.html
Yes, hydraulic fluid comes in 32, 46, and 64 weights. 64 will probably make it work a little longer. You could have something easy to fix also, like a leaky relief valve causing the hydraulics not to work at low speed, and similar dirt in the steering causing it to be erratic. Or air getting into the fluid and causing the issues.
There is also Lucas Hydraulic Booster. It is kind of like STP but made for hydraulic oil. I would check for oil contamination as well as the other suggestions.
The issue comes down to how hard and expensive is it to fix the problem with the pump. Do you have to split the tractor for access or is the pump mounted on the outside with easy access. The spec sheet I looked at showed the pump as being only 11 gallons a minute. That's not much of a pump so expense for the part should not be that onerous. Heavier oil will only save you until it gets to the new high temperature. Heavier cold oil will function slower and heat up faster usually meaning you have a little larger time frame before things start to act up. If the problem is in fact the pump the thicker oil trick will not last long before you go back to the same operating time frame you have now. It may also present a safety issue for steering while operating cold.