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bobcat s300 cavitating

JB22 ยท 2018-03-26 21:04

My 2006 s300 is cavitating in the hydraulic system so bad it comes out the vent cap. When it first started it would clear out when the machine warmed but now its all the time. Has anyone out there had this problem? Already changed filters,oil and have no crazy leaks anywhere. Checked with bobcat and they have never heard of this happening either so i'm turning to anyone who can help because i cant be the only one this has happened to. Any help is appreciated.

Replies11
  1. #1Wes J2018-03-27 07:55

    I believe what you are describing is called "aeration" and not cavitation. Typically that is caused by a leak in the suction side of the pump. It's a leak that allows air in, but not oil out. Typical culprits are the pump input shaft seal, the suction side hose and connections, or the pickup tube in the tank. Sometimes you can put some oil or grease around the input shaft seal and see if the issue stops momentarily. But, on a Bobcat that likely requires removing the pump.

  2. #2Tenwheeler2018-03-27 20:32

    Wrong fluid?

  3. #3JB222018-03-27 22:18
  4. #4JB222018-03-27 22:35

    Thank you. You are the second person to tell me that you can have air suction and no fluid loss. Had little time today to inspect the suction side but so far all looks ok and i will continue looking tomorrow. When i find the problem i will make sure to post it. Thanks again

  5. #5JB222018-03-27 22:36
  6. #6JB222018-03-27 22:37

    I use only Bobcat brand.

  7. #792U 34062018-03-28 11:20

    A lot of times on the larger excavators I worked on the suction hoses would get rock hard from the heat. You could ratchet the hose clamps down as tight as possible and they'd still suck some air in.

  8. #8mikebramel2018-03-28 12:04

    Exactly 100%

  9. #9gta182021-11-10 10:23

    @JB22 , did you ever figure out the cause of the cavitation?

  10. #10Delmer2021-11-10 21:08

    Didn't notice this was an old thread, but the two best answers are here already. Old fluid, or water in the fluid will compromise the antifoam additive in the oil. But if it happens fast, then it's a suction air leak.

  11. #11gta182021-11-11 10:45

    Thanks, I didn't read thoroughly. So, mine would be intermittent cavitation sound and also I have a drip whenever I use mine, I get a drip from the bottom of my pan (I think this doesn't have the cover at the bottom anymore. I probably have to find the leak and hopefully will fix the cavitation as well. Is STP AW32 brand oil fine with the Bobcat 753?