Radical fix for a very radical problem

[Matchstix]

Contact AMT composites, they might have the correct product and advice.

If air is coming out water might be going in. Check for that.

Try and pressurise the steere and place the crown assembly under water and see if air comes out the other side?

[BaGearA]

The O ring on that top cap is made to seal against the inside of the fork stanchion above the threads. If it is the correct size, clean and well lubricated with no scratches inside the stanchion tube or the O ring groove, it WILL seal.

 

This means that air is probably NOT exiting into the crown from the top cap joint. The leak is somewhere else and it can only be a hole or crack in the stanchion tube. This brings up the obvious questions of how did it happen and will it be safe if you manage to seal the leak without repairing the structural damage.

 

If you do try an epoxy type repair to seal the leak then the best way to ensure it withstands the pressure is to apply it from the inlet side of the leak rather than patching over the exit point which hardly ever works. However you don't have access to the source side of the leak so use a fairly fluid epoxy and pressurise the steerer tube for a few minutes after adding the epoxy. This will force the liquid epoxy in reverse through the leak path where it will solidify and cannot be displaced by future pressure.

 

Still have my reservations about that stanchion though.

 

Sent from my SM-G935F using Tapatalk

possibly yes but i would also expect oil to come out then. ( and quite a lot this fork uses 5ml on top of the airshaft and 15ml in the lower leg)

 

Structure wise I am not worries , I've heard incredible stories of people falling and breaking lowers, wheel , bending steerers , and even breaking the fork out of the headtube but never a stanchion.

 

I'm not exactly sure what they are made of but its has to be something bloody damn strong.

 

I don't think there is much to worry about regarding a stanchion breaking, if this is even what you are concerned about?

[BaGearA]

Contact AMT composites, they might have the correct product and advice.

If air is coming out water might be going in. Check for that.

Try and pressurise the steere and place the crown assembly under water and see if air comes out the other side?

will try 

[V12man]

If you can figure out a way to seal it - I can lend you a vacuum pump to try suck epoxy through - but I suspect that crown has a cracked and is toast.

[ichnusa]

All very impressive and a successful repair will be an absolute bonus.  Either way it seems like a manufacturing fault and warrantee to me...

[Eddy Gordo]

I was actually thinking of trying to get one that works with modern smartphones 

 

 

http://www.ebay.com/itm/New-Android-Endoscope-Waterproof-Borescope-Micro-USB-Inspection-Video-Camera/121997170733?_trksid=p2047675.c100012.m1985&_trkparms=aid%3D777003%26algo%3DDISCL.MBE%26ao%3D1%26asc%3D38530%26meid%3D5d674389962a40d399b4d92a4d8484a7%26pid%3D100012%26rk%3D3%26rkt%3D10%26sd%3D171827746965

 

 

something like that ^

Maybe if you know someone with the new CAT phone. It has a thermal camera and that could possibly reveal the source

[JA-Q001]

The O ring on that top cap is made to seal against the inside of the fork stanchion above the threads. If it is the correct size, clean and well lubricated with no scratches inside the stanchion tube or the O ring groove, it WILL seal.

This means that air is probably NOT exiting into the crown from the top cap joint. The leak is somewhere else and it can only be a hole or crack in the stanchion tube. This brings up the obvious questions of how did it happen and will it be safe if you manage to seal the leak without repairing the structural damage.

If you do try an epoxy type repair to seal the leak then the best way to ensure it withstands the pressure is to apply it from the inlet side of the leak rather than patching over the exit point which hardly ever works. However you don't have access to the source side of the leak so use a fairly fluid epoxy and pressurise the steerer tube for a few minutes after adding the epoxy. This will force the liquid epoxy in reverse through the leak path where it will solidify and cannot be displaced by future pressure.

Still have my reservations about that stanchion though.

Sent from my SM-G935F using Tapatalk

 

Atleast we understand each other.

[SCD]

stanchion threads

 

A different theory. Much easier if I am right.

 

But first a comment to the epoxy. I doubt it will be able to seal the leak if there is one. Two reasons. Firstly the material you are trying to bond to is most likely contaminated. Flooding it with degreaser will wash some of the contamination off but this will not be possible in the fine cracks and fissures where you want to get to. Worse, these are now contaminated with degreaser, not really a bonding agent, even if dried up. 

Secondly most resins shrink when they cure, Epoxy included. I will debond from the non-perfect surface and allow air to pass. The effect is worse where you pour bulk volume because of the curing heat and the temperature shrinkage.

 

Now my take on a solution: By looking at the photo of the top of the stanchion and the aircap with the seal it looks like the seal is not pressing against the aluminium but a thin carbon lip that covers the top of the stanchion tube. Now while you seal the top properly the air may have found a path between alu and carbon, entering the steerer body and show up where you discovered it. Take a Stanley knife and remove this carbon/resin until the full top of the stanchion tube is exposed. Obviously don't scratch it. Now your seal should not be compromised anymore

 

Curious to hear if this works out.

[King_Crispy]

Now it's a dual air.

Throw it away. The time you've wasted on it isn't worth the old fork.

[mazambaan]

From left field. Try Google and your local rep for Loctite. I fixed a magnesium porous water pump casing after welding (not easy to weld flammable metal properly) with some magical product that wicked (not wick ed) its way into the porous sections.

[BaGearA]

A different theory. Much easier if I am right.

 

But first a comment to the epoxy. I doubt it will be able to seal the leak if there is one. Two reasons. Firstly the material you are trying to bond to is most likely contaminated. Flooding it with degreaser will wash some of the contamination off but this will not be possible in the fine cracks and fissures where you want to get to. Worse, these are now contaminated with degreaser, not really a bonding agent, even if dried up. 

Secondly most resins shrink when they cure, Epoxy included. I will debond from the non-perfect surface and allow air to pass. The effect is worse where you pour bulk volume because of the curing heat and the temperature shrinkage.

 

Now my take on a solution: By looking at the photo of the top of the stanchion and the aircap with the seal it looks like the seal is not pressing against the aluminium but a thin carbon lip that covers the top of the stanchion tube. Now while you seal the top properly the air may have found a path between alu and carbon, entering the steerer body and show up where you discovered it. Take a Stanley knife and remove this carbon/resin until the full top of the stanchion tube is exposed. Obviously don't scratch it. Now your seal should not be compromised anymore

 

Curious to hear if this works out.

I'm sure this will work but I doubt that is where the leak is coming from , will try anyway and report back going to few stores tomorrow to pick their brains and get advice.

[droo]

This is a common issue with RS Blackbox crowns, and it's caused by a poor seal between crown and stanchion. JXV got it right. (As he does quite often.)

 

Good luck with the fix, I'll be following this thread with interest.

[DJR]

This is a common issue with RS Blackbox crowns, and it's caused by a poor seal between crown and stanchion. JXV got it right. (As he does quite often.)

 

Good luck with the fix, I'll be following this thread with interest.

Listen to this guy, if anybody knows his forks inside and out, it is Droo!

[Shebeen]

Maybe if you know someone with the new CAT phone. It has a thermal camera and that could possibly reveal the source

I got one (two actually), but it's not an xray camera, haven't really been able to use it for leak detection yet.

[Skinnyone]

It wasn't unheard of for those forks (Specialized Brain) to have that leak, they would warranty or replace the forks as a whole with a pay in...if you're the original owner.

 

Perhaps speak to Spez and see if they could do anything? the problem is they are old so not sure they would have spares anymore....