2008 GG280 pro oil/antifreeze mixing?

Discussion in 'Trials' started by jontow, May 12, 2017.

  1. jontow

    jontow Been here awhile

    Joined:
    Jun 14, 2011
    Oddometer:
    115
    Location:
    Northern NY (with extra north)
    Last season I tore into my GG280 to replace a visibly leaking base gasket. After getting it back together, everything was fine, but late in the season my transmission oil started to go milky and my coolant level started to drop. I'm strongly aware of what this means in other vehicles, but would like to solicit opinions from more knowledgeable folks than I about where this leak could be in this particular engine?

    Things that I've done in the past that might be related:
    * pulled the water pump out of the case (but haven't removed the snap ring to get a look at the insides of it) -- water pump currently pulled again but I can't find any play in the shaft and the seal *looks* fine? better way to test this? maybe dribble a bit of coolant in and make some plugs / put a few psi in with a hand pump and see what happens?
    * pulled the head (replaced both orings upon reassembly)
    * pulled the jug (replaced base gasket with thicker heavyweight paper gasket upon reassembly)

    These seem to be the only areas that have coolant flowing in them at all. I would rather not pull the head/jug again unless someone indicates it as a strong possibility, but hey, the bike isn't moving until I sort this out so :bash
    #1
  2. laser17

    laser17 Long timer

    Joined:
    Mar 6, 2008
    Oddometer:
    1,302
    Location:
    Boston,Massachusetts
    The most likely failure is the Water Pump shaft wears and develops a groove that creates the leak past the seal. Replace the shaft and seal is the fix. seal alone won't do it.
    #2
    jonnyc21 and 10K like this.
  3. jonnyc21

    jonnyc21 Trials Ninja

    Joined:
    Feb 8, 2011
    Oddometer:
    2,495
    Location:
    Boise aria
    laser17 has it spot on. Most common cause is the water pump shaft, new shaft and seal should fix it right up.
    #3
  4. Fuzzy Wrench

    Fuzzy Wrench Pick Your Tool

    Joined:
    Jan 11, 2013
    Oddometer:
    14
    Location:
    Golden, BC
    I concur... Most likely water pump leak..
    #4
  5. lineaway

    lineaway Long timer

    Joined:
    Oct 1, 2011
    Oddometer:
    6,524
    Location:
    nm
    It`s not something new, ever since 1979 the only two ways that oil can mix with the water is the water pump or cracked cases. On a two stroke (except the early 95 gas gas ) the top end cannot mix with the oil.
    #5
    jontow likes this.
  6. jontow

    jontow Been here awhile

    Joined:
    Jun 14, 2011
    Oddometer:
    115
    Location:
    Northern NY (with extra north)
    Well, thanks folks; all of this confirms what I suspected without buying parts.. now it's time to go buy parts :rofl
    #6
  7. jontow

    jontow Been here awhile

    Joined:
    Jun 14, 2011
    Oddometer:
    115
    Location:
    Northern NY (with extra north)
    I haven't reassembled it yet (probably tonight's project, tbh) but I figured I'd share a few photos now that I have the new parts to compare with. It's pretty obvious that the advice in this thread was right on: you can see some seriously deep grooves in the shaft, compared to the new one which has no grooving at all:
    [​IMG] [​IMG]

    Discovered an easy way to press old seal+shaft+impeller out of water pump: U-joint/ball-joint press without any cups, and a socket style allen bit: maybe 7mm? size big enough to match the small end of the shaft but clear the inspection opening in the water pump body.

    Thanks again for the helpful hints.
    #7
    LemmeTry likes this.
  8. LemmeTry

    LemmeTry Over-thinker...

    Joined:
    Jan 27, 2016
    Oddometer:
    126
    Location:
    Jasper, TN
    It's really helpful when folks come back after asking a question and post pics like you've done for the sake of someone with a similar situation down the road. So just wanted to say "Thanks!" :thumb
    #8
    jontow likes this.
  9. motobene

    motobene Motoing for 46 years

    Joined:
    Mar 9, 2013
    Oddometer:
    3,983
    Location:
    Wichita Mountains SW Oklahoma
    Looks like classic seal lip compression wear. I wish they'd harden the shaft more.

    Love that GasGas pro simplicity! The water pump shaft inner bearing is the crank main bearing. The outer is the brass plug.

    If the main bearings have slop (usually not), it will excite the water pump shaft and increase wear rate.

    Don't forget the small thin washer between the pump shaft tip and the brass plug. It's easy to drop that into the pump cavity.
    #9