Why Is My Hydraulic Pump Flood Always Black

Discussion in 'Mechanic and Repair' started by Tennesseepowerstroke, Apr 28, 2013.

  1. piston slapper

    piston slapper LawnSite Platinum Member
    Messages: 4,337

    My apologies to OldTimer and the rest of the Exmark dealers visiting this site...
    Bashing Exmark is not something I have done very often..It just seemed like the right thing to do...
    I have always been more interested in getting to the solution...no matter where the blame lies..
    That trait has made me an above average tech ...gaining both the respect and the fear of more than a few dealerships...
    Team players tow the company line...Team leaders get the job done...

    The idea that Mobil 1 turns black in any hydro system is completely alien to me...
    If Im wrong..so be it...Id love to hear it from the fine people at Mobil...themselves..
  2. Greg78

    Greg78 LawnSite Silver Member
    Messages: 2,010

    I didn't take it as bashing. Just calling it like you see it.
  3. piston slapper

    piston slapper LawnSite Platinum Member
    Messages: 4,337

    The dealers that sell the high dollar hydro fluid will...
    If there is an issue...they would rather keep it " in house "...than broadcast it in an open forum..
    They live in a world where they have all the answers...and you need them.
    Calling them like I see them has taken more than a few job opportunities off the table over the years..
    But...Me and the dogs eat pert near every day...
  4. Greg78

    Greg78 LawnSite Silver Member
    Messages: 2,010

    Sure last time I talked to "my" dealer they told me metal shavings in the hydro reservoir were normal!!! I take everything they say with a grain of salt.
  5. piston slapper

    piston slapper LawnSite Platinum Member
    Messages: 4,337

    Somebodys got to have a valid explanation for Mobil 1 turning black in a hydro tank after only 10 hours run time...
    Those corporate guys sure got quiet....might be time to send a sample of that fluid to the lab for analysis...
  6. tyler_mott85

    tyler_mott85 LawnSite Senior Member
    Messages: 582

    I was bored so did a little googlesearching on black hydraulic fluids. A few things stood out.

    One, some oils and their additive packages may discolor if they come in contact with an adverse metal. Like perhaps copper, or some ball bearings will have an adverse reaction. I do not understand working of hydraulic pumps or hydraulic gears but if your fluid was to come in contact with a ball bearing it may have a chemical reaction and cause the fluid to turn colors. This would align with reps recommendation to change your fluid to different brand.

    The second was Micro-dieseling. Which is when small bubbles of air entire the system and when going from a low pressure zone (reservoir tank) to high pressure zone (pump) will compress the air dividing it into it's individual elements which will then have chemical reactions to metals and/or chemicals in the oil itself, again turning the oil black. I relate this to the possibility that there was a need to fill the new filter with oil before installation, to "prime" it as sorts, and if it was not done as the oil was pumped into the dry filter it carried away air into the systems high pressure areas where micro dieseling would occur.

    A third option was moisture getting into the system and contacting ferrous metal which would immediately rust and have adverse reaction to oil causing discoloration, but I don't see this as being a viable option unless the mower was exposed to the elements without fluid in it, or filter attached, or the fluid change was done in high humidity conditions.

    Either option you take I agree with piston slapper to send an oil sample off to the lab to see what they can tell you about it.
  7. Tennesseepowerstroke

    Tennesseepowerstroke LawnSite Senior Member
    Messages: 366

    The filter was filled before with Mobil 1 15W50 before installation. There was not any moisture introduced to the system as it was done in dry 70 degree weather. Can you recommend a good lab that will do an anylisis at a reasonable price? The system probably did get a little air in it as I had to add more oil a couple of times after operating for about 5 minutes.
  8. Greg78

    Greg78 LawnSite Silver Member
    Messages: 2,010

    I doubt air is the cause. I had a pump sucking air for weeks on end and my fluid never changed.
  9. piston slapper

    piston slapper LawnSite Platinum Member
    Messages: 4,337

    Tyler...I went thru all those mental gymnastics before I initially chimed in..the benefit of the doubt didn't apply here...
    There is something bad wrong when 2 guys with newer Exmarks chime in with the same blackening of the fluid problem...
    Exmark dealt themselves a bad hand...though it may be a year or 2 before it becomes common knowlege...
    Even my buddies are tight lipped....this could get interesting....
  10. R & R Yard Designs

    R & R Yard Designs LawnSite Senior Member
    Messages: 646

    Sent a sample to Blackstone labs in fort Wayne in. And let them know what is going on and they will find out what metals are in there.
    Posted via Mobile Device

Share This Page