I was working my 1970 4000 yesterday doing some bush hogging and discing. I had a little problem when lifting my implements. After about an hour of work, my lift would fail to lift up the implement or it would only lift it partially. If I turned off the engine and restarted it, then the lift would work just fine. This hapened once or twice more but seemed very randon. Its not a real big deal, but I am wondering if I am heading for a problem or if this might be a simple fix? Hydraulic fluids are fresh.