High oil pressure FH680D

Discussion in 'Mechanic and Repair' started by Coachbob, Jun 12, 2019.

  1. Coachbob

    Coachbob LawnSite Member
    Messages: 239

    as i have posted in other threads i had this motor torn down and found the oil pressure relief valve stuck in its seat. I got it out and cleaned the ball, which was corroded. I tested spring and everything seemed ok to me.
    In the interest of not wanting to blow this engine yet again, i took oil pressure readings from the oil port shown below. I couldn’t get a socket around the pressure switch, but the fh680 manual says these ports are okay for testing. I am getting readings of 50-60 psi from a warm engine at 3000 rpm. Drops to about 35 at idle. Using 10-30 oil. Not sure if i would get a lower reading out of the switch port or not. Any thoughts on 60psi and risk to engine? Or any other ideas before i pull the cover off again would be appreciated.

    AA0475F2-6D45-41F8-8CDC-0242E77245BD.jpeg
     
  2. Walker56

    Walker56 LawnSite Fanatic
    Messages: 12,155

    In my opinion, the oil pressure is too high. There may be something still wrong with the relief ball and or spring. The manual calls for 35-45psi max. The service level for the relief spring is 0.77”
     
  3. OP
    OP
    Coachbob

    Coachbob LawnSite Member
    Messages: 239

    I guess i better not risk it. I’ll pop the cover off this weekend and take a look.
     
    TrainingWheels likes this.
  4. flintknapper

    flintknapper LawnSite Member
    Messages: 192

    That would be best. Also, looks like you added an oil cooler. Make sure you don't have a restriction there (oil cooler/oil filter).
     
    TrainingWheels likes this.
  5. OP
    OP
    Coachbob

    Coachbob LawnSite Member
    Messages: 239

    So, i had a quart of motor medic flush in the garage, so i decided to try it since it’s been there for a couple years. I ran the engine with the flush and drained it. Filled with same 10-30 but didn't have a new filter handy. After it warmed up it was reading 46 PSI on the gauge at wot. The drained oil and flush was dirtier than the bit i drained before adding the flush, but not sludgy. Do you think this stuff cleared some blockage that was causing the high pressure condition? Maybe it freed up the relief valve passage?

    Edit. When i say same 10-30, i mean new oil, just same brand and weight.
     
  6. Walker56

    Walker56 LawnSite Fanatic
    Messages: 12,155

    If that is the case, I would be concerned that as the replaced oil circulates, any dirt left behind could eventually clog a passage and then you could have bigger issues.
     
    TrainingWheels likes this.
  7. OP
    OP
    Coachbob

    Coachbob LawnSite Member
    Messages: 239

    Short of a complete tear down, what would you suggest? I was going to run another flush tomorrow, and possibly a third. It seems if this stuff freed up something, it would have to be in a passage, the oil cooler, or around the pressure relief valve. I thoroughly cleaned the engine prior to assembly and blew air through the passages. I brushed the passage where the relief ball travels as well until it was moving freely. I don’t recall cleaning out the oil cooler, so am suspecting it was dirty when I assembled. I suppose i could put a dash mount pressure gauge on one of the ports and keep an eye on it.
     
  8. Walker56

    Walker56 LawnSite Fanatic
    Messages: 12,155

    @Coachbob , do what you feel comfortable with. You thoroughly cleaned the engine and when started, the oil pressure was high despite cleaning the passage where the ball travels. A flush cleaned more junk out and obviously had an effect on the oil pressure. I would not hazard to guess how many more flushes it would take. One, two?
     
  9. OP
    OP
    Coachbob

    Coachbob LawnSite Member
    Messages: 239

    Thank you for your thoughts; much appreciate the input. I have since read many people say not to put that flush in your engine. In this case it seems I took a step forward, but like you said, I might have opened a can of worms. To access all the passages, I would have to remove the crank, the cam, basically everything that gets oiled. argh! I think I might just put some detergent oil in and do some quick changes to see how it looks. probably add a gauge too.
     
  10. flintknapper

    flintknapper LawnSite Member
    Messages: 192


    ^^^^^^


    The oil coolers for these FH series engines appear to be 'sand cast' and pretty rough examples (at least mine is) at that.

    It certainly wouldn't hurt to remove it, inspect it for an internal obstruction and clean it. While you have it off, re-install the original 'pipe' that the oil filter screws onto, put a NEW filter on it and run it for a bit. Check to see IF the pressure is closer to normal. If it is...then you might have found your source (filter or oil cooler), if not...then you are back to going into the engine.
     
    Coachbob likes this.

Share This Page