Fox DHX 3/4/5 Coil - Oil and o-ring replacement guide

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Fox DHX 3/4/5 Coil - Oil and o-ring replacement guide
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Posted: Apr 25, 2017 at 10:50 Quote
CMMUNCHIES96 wrote:
Is this rebuild good for DHX RC 4

No, for the 2010-2013 DHX RC4 you want FX-803-00-379 For the 2014 and 2015 model you want FX-803-00-828

If you come by or e-mail dunbar ill sell you the kits you need.

Posted: May 7, 2021 at 13:22 Quote
Hope someone can help me with my issue. It’s driving me absolutely nuts. I have a fox dhx 4.0 coil shock.

On sharp compression at any point in the stroke, i get a knocking sound. Ive replaced and looked at every bearing and bushing through the entire rear suspension system, and tested things individually to isolate where the sound is coming from. So i know for sure its coming from the shock.

With the correct amount of air in the boost valve, the sound occurs. If i reduce the pressure to nearly 0 psi, the sound goes away. (Of course i dont ride it at 0 psi, its just for testing purposes off the bike). I flushed all the fluid and reset ifp depth to 34mm (where it is intended for my eye to eye and stroke length), and added some fresh new 10wt. Still the problem is there.

Even with the shock off the bike, and no coil installed, you can get the knocking sound to occur by sharply applying pressure to compress the shock. So it isnt the coil possibly making the noise.

My theory is that its something to do with the IFP. Maybe on sharp compression its rotating slightly in the chamber and making metal to metal contact with chamber walls? If this is true, that leads me to believe there is something wrong with the o ring on the IFP itself. The o ring looks to be in good condition and is well lubricated. Though I don’t have a new one to compare it to, so maybe its worn out?

Even with the knocking sound at the beginning of sharp compression, the shock still travels smoothly afterward.

It feels like it functions properly when out on the trails, but the knocking sound is driving me crazy. Its basically all I hear the entire way down the trail.

If anyone has had this happen before or could shed some light on what my next steps could be, please don’t hesitate to reply! Any help is greatly appreciated.

Posted: May 25, 2021 at 13:41 Quote
It's a worn boost valve spring.

Posted: May 29, 2022 at 12:11 Quote
Hey I got a 2008 dhx 3.0 coil and went to rebuild it and then some of the shims fell out I have all of them but don’t know what order they go in stone able to help thanks

Posted: Jun 27, 2022 at 7:44 Quote
Bryden-smith wrote:
Hey I got a 2008 dhx 3.0 coil and went to rebuild it and then some of the shims fell out I have all of them but don’t know what order they go in stone able to help thanks

You can use the same valve orientation as the Van RC or Bomber CR Coil. All that info is available from Fox

Posted: Jul 5, 2022 at 14:44 Quote
z-man wrote:
Bryden-smith wrote:
Hey I got a 2008 dhx 3.0 coil and went to rebuild it and then some of the shims fell out I have all of them but don’t know what order they go in stone able to help thanks

You can use the same valve orientation as the Van RC or Bomber CR Coil. All that info is available from Fox


Ok awesome thanks

Posted: Sep 4, 2022 at 5:58 Quote
z-man wrote:
pbuser45684 wrote:
Anyone know where to get an O-ring kit for DHX 5.0? I think OP isn't around any more and not having much luck on ebay or google. Thanks.

Dunbar cycles!

FX-803-00-122

Could you please tell what is the difference between 803-00-142 and 803-00-122?
I would like to change all O-rings and seals including the "piggyback" part and do not know which set to buy.

Posted: Sep 7, 2022 at 7:32 Quote
kona-n wrote:
z-man wrote:
pbuser45684 wrote:
Anyone know where to get an O-ring kit for DHX 5.0? I think OP isn't around any more and not having much luck on ebay or google. Thanks.

Dunbar cycles!

FX-803-00-122

Could you please tell what is the difference between 803-00-142 and 803-00-122?
I would like to change all O-rings and seals including the "piggyback" part and do not know which set to buy.

803-00-142 is for all of Fox's air sleeves and won't work on anything coil related. 803-00-122 is what you want.

Posted: Sep 9, 2022 at 11:23 Quote
z-man thank you for your answer!
I actually misread the thread, because I have DHX 5.0 Air. So I contacted Fox's support and got infromation that, in order to change all of seals, I also need 803-00-122 for "oil side" and 803-000-143 for air chamber.

Posted: Sep 29, 2022 at 7:23 Quote
kona-n wrote:
z-man thank you for your answer!
I actually misread the thread, because I have DHX 5.0 Air. So I contacted Fox's support and got infromation that, in order to change all of seals, I also need 803-00-122 for "oil side" and 803-000-143 for air chamber.

For the DHX air you want a 803-00-143 and 803-00-142. 802-00-122 is for coil shocks.

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