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  1. #1
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    Question Rebuilding Shocks Issue -- air entering into shock

    my slash is like 9 years old, but only driven like a few times. i bought it new.
    while i drove it like years ago, one of the shock cover's popped off. So i could not drive it anymore and the car has sat since.

    I am replacing the shocks caps with aluminum caps and adding new oil. The rest of the parts are clean and look ok.

    I am having issues at the stage of trying to bleed the air out of the shock:
    1) I raise the plunger arm up and down to get rid of the air bubbles from the bottom,
    2) let it sit for 5 min and the air bubbles at the top are gone.
    3) i close the cap with the silicone diaphram
    -i then later move the rod up and down and can hear air squishy noise.

    so i took the cap and diaphram off and notice:
    - so this time, instead of doing step 3 above, i repeat step 1 and 2 and i still keep getting bubble every time i start raising and lowering the plunger.
    -i let it sit and repeat and more new air bubbles....

    what is happening? i would like to fix these shocks and keep and extra pair on hand.


    on another note, since i couldn't get rid of the air:
    I bought new shocks and i couldn't hear any air in it. The new shocks have a plastics cap and i need to change it to the aluminum once, but i'm afraid, once i take the caps off I'll be introducing air in the shock and the whole problem will start again...

  2. #2
    RC Racer
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    Quote Originally Posted by RangerHarry View Post
    my slash is like 9 years old, but only driven like a few times. i bought it new.
    while i drove it like years ago, one of the shock cover's popped off. So i could not drive it anymore and the car has sat since.

    I am replacing the shocks caps with aluminum caps and adding new oil. The rest of the parts are clean and look ok.

    I am having issues at the stage of trying to bleed the air out of the shock:
    1) I raise the plunger arm up and down to get rid of the air bubbles from the bottom,
    2) let it sit for 5 min and the air bubbles at the top are gone.
    3) i close the cap with the silicone diaphram
    -i then later move the rod up and down and can hear air squishy noise.

    so i took the cap and diaphram off and notice:
    - so this time, instead of doing step 3 above, i repeat step 1 and 2 and i still keep getting bubble every time i start raising and lowering the plunger.
    -i let it sit and repeat and more new air bubbles....

    what is happening? i would like to fix these shocks and keep and extra pair on hand.


    on another note, since i couldn't get rid of the air:
    I bought new shocks and i couldn't hear any air in it. The new shocks have a plastics cap and i need to change it to the aluminum once, but i'm afraid, once i take the caps off I'll be introducing air in the shock and the whole problem will start again...
    Air won't just shoot itself into the silicone oil, it has to be introduced via leaving air space inside the shock body then extending which creates a sucking action underneath the piston, and PULLS air into the shock.

    A lot of folks dont realize, you can, (too easily) sometimes, WAY OVER TIGHTEN the shock caps, which ends up binding the diaphragm inside, instead of sealing nice against it... It creates an air gap, which your shaft/piston ends up squishing, and retracting, and in doing so, the diaphragm (which is its own-self-contained air pocket) induces air into the oil after only a couple of *what the HECK is that weird sound at the end of compression* "bleeding strokes". Also, if u think slow, is slloowww, WRONG. i mean you wanna go up and down slow!

    Also, empty the shock as best you can/wipe off top of piston, fill the shock body ONLY 1/3-1/2 full!!! This helps IMMENSELY! , BLEED THE AIR, LET SIT, FILL ANOTHER 1/4-1/3 FULL AT EACH "TOPOFF"... THEN THE LAST FILL SHOULD BE UP TO THE RIM OF THE SHOCK, THEN, MOLASSES-LOVING-SLUG-SLOW, move that shaft up and down, DO.NOT. go too close and certainly NOT over the fill level of oil!!! That is what induces air! When done correctly, after sitting a few min (yet again) the level should be literally ONE, MAYYYBE 2, hairs-away from the rim.

    After gently, PROPERLY setting diaphragm in its proper place (first, remove, wipe off with clean rag, and THEN install into cap). Stuff the darn cap on whilst tightening till she stops with finger-only strength, PLUS, call it..1/16th of a full turn. Check results.

    I have had multiple erroneous attempts at bleeding shocks on multiple RC vehicles and I'm still not quite used to it so I know ahead of time when I'm bleeding shocks if it's all for I need to allow way more than just 20 to 30 minutes in order to try again, try again, try again, NAIL IT!! LOL

    I strongly suggest checking out YouTube for proper shock bleeding and rebound setting tips there's short videos such as 2 minutes 34 seconds, there's also videos over 20 minutes long, watch a few short ones and you'll get the gist whether from the video, or your own trial and error.
    What you will notice, is each person in different videos has their own description/method/"rules" for rebuilding their shocks.

    I recently discovered the rebound part of rebuilding and that makes it even more difficult for me to properly bleed my shocks for some reason? But I take the frustration with a grain of sand and keep trucking, before I know it I'll have it down to four shock rebuilds and under 20 minutes, eyes closed, one hand behind my back....blah blah blah.
    Cheers!

    Sent from my Pixel 3a using Tapatalk
    Last edited by ksb51rl; 11-05-2020 at 10:53 PM. Reason: Language and Content

  3. #3
    RC Champion zedorda's Avatar
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    Did the shocks have bubbles in them before you took them apart? And are the shaft seals in good shape? And are the shafts in good shape without scratches? The shaft hole is a common point of air intrusion.

  4. #4
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    Thank you for explaining the whole process and the problems I could be facing. I am practicing on the shocks right now and it is hard. The videos i found weren't that help full. A lot of them didn't cover a lot of what you said and were showing them moving the piston up and down at normal speed, not slowly like you said. If you know of a good video can you please send me the link?
    Thanks

  5. #5
    RC Qualifier Calebs0615's Avatar
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    Make sure to pump the shock while your emptying it. There's fluid that goes inside of the piston under the piece that moves up and down.

    Sent from my LGL722DL using Tapatalk

  6. #6
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    RH, I've read through this. My 2 cents. If those shocks have set for 9 years, I would bet the seals in the body at the (seal head) in real shock terms are bad (non pliable) and letting air in or the bore is worn out, you need to replace them. It sounds like you are bleeding them correctly. Also, when you have them back together and you cycle them through the stroke and you can hear noise inside it may be the fluid going through the piston and not air. I have a small bussiness and specialize in real vintage motorcycle MX shocks,.so I'm pretty sure I know what I'm talking about.

  7. #7
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    ill make sure to pump it when emptying.

    I thought it was the fluid moving too, but the piston doesn't come out all too much. I do think the bottom seal has gone bad so I
    may replace them

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