[JimLad]

I have rebuilt this a few times but I have a problem. It seems to cavitate immediately. Then, when I depressurise the boost valve and unscrew the resevoir cap, once I get to the end of the threads the cap and the IFP explode out of the resevoir followed by a fountain of foamy oil. And this is soon after a rebuild (just having cycled the shock a few times).

All the internals look ok, I can't see any signs of damage but clearly something is wrong. Does anyone have a list of the sizes of o-rings that I could replace...perhaps the IFP o-ring is suspect and letting air past the piston into the oil? Is there something else that could be causing this.

 

[Sandwich]

any chance dirt got in your shraeder valve? I had that happen to me once. I failed to use a cap on it, and when I went to check the air pressure, a little dirt got in and kept that valve open....

yours sounds more like residual pressure inside though, so I'm not sure the schraeder would help.

 

[wood booger]

Sounds like bad IFP o-ring. You sould be able to find a replacement if you pull it off. They go by width (cross section of o-ring) and diameter. You can try asking Fox, but sometimes they don't give out info or sell small parts to individuals. Maybe you will get lucky.

Also check the inside of the reservoir to make sure there are no knicks or gouges, check the bleed screw and o-ring, and the IFP itself. Somtimes plastic IFP's can get a hole in them, but yours should be metal so it should be okay.

I would say it is definately and IFP issue.

 

[JimLad]

I actually replaced the schrader valve because it seemed to be losing a lot of pressure when I disconnected the pump and I thought that was why the oil was cavitating. Guess it wasn't the only thing!

Anyway I will go tomorrow to a local supplier and try and acquire a replacement o-ring for the IFP. I managed to track down a list of the o-ring sizes in the dhx from google. I did check the inside of the resevoir for damage but didn't see any.

 

[JimLad]

Ok so it turns out the IFP is worn. Somehow the two metal flanges that should be flush with the chamber have worn down on opposite sides, allowing the piston to tilt in the chamber and when this happens I think air leaks past the seal. And this doesn't seem to be available as a spare.

What a crap design

 

[Udi]

I have a spare DHX5 IFP if you can't find one.
PM me your email if you want to work something out.

 

[JohnnyC]

I've never heard of an IFP scratching the side, is it possible the reservoir has been dented or slightly ovalised?

 

[JimLad]

No obvious sign of any damage to the resevoir. It's like it started to tip in the chamber and wore away at those points. Pretty weird...

I'm trying to get one machined at work, we'll see what can be done. I'll bear your offer in mind Udi but I'm in the UK.

 

[wood booger]

No obvious sign of any damage to the resevoir. It's like it started to tip in the chamber and wore away at those points. Pretty weird...

I'm trying to get one machined at work, we'll see what can be done. I'll bear your offer in mind Udi but I'm in the UK.

Weird. Shouldn't be hard making one, that is a pretty basic lathe part. I would spit one out for $25.

I would be more concerned with what allowed it to tip and wear like that. Like maybe the IFP OD was not correct.

 

[JimLad]

Alright so I went for a bit of a halfway house to save some time and got a little plug turned on a lathe that fits into the back of the IFP. Like a tophat shape with a hole through the middle for bleeding, and metal epoxied this in place. So the piston is now about 3mm longer with the plug acting as a new lip to prevent movement.

I just installed it and the play of the piston in the resevoir has been eliminated. Then I rebuilt the shock, and its nice and silent when cycled- no more squelching. So I think it's fixed