FX Impact Leak

Regulator piston o-ring.

https://www.youtube.com/watch?v=bSscQBR6hWA

+1 on the piston o-ring. Should be a rather simple fix, just take care not to nick other o-rings during removal + installation.

Your o-ring is 4 x 1.5 Buna 70

This thread has links to buy all the o-rings and schematics. https://www.airgunnation.com/topic/impact-o-ring-list-corrected-with-links/

I just finished rebuilding my regulator. before taking it all apart, what's the reg pressure set at? Anything under 120 bar will cause a leak because there are two O-rings on the center brass bit. Under 120 or 130 bar the back o-ring doesnt' make contact and it leaks, pretty quickly.

If you do have to rebuild, the complete kit including post, brass parts, rings and bellville washers is about $45 from FX USA - 866-639-0772. They ship parts on Wednesday, so if you order Thursday, it'll be a week before it ships. Order on Tuesday.

If you can avoid changing out the O-ring that sits inside the gun body (9x1.5) DON'T change it unless you have to. Getting the replacement in is a royal pain in the *&*&^. The rest of the O-rings are pretty easy. Follow the instructions in the video and you'll do fine, just be extremely patient.

Yep. Don't overcharge your gun , on purpose or by accident, or it will leak!

I had the same issue, bought some o-rings based on what I read on AGN. Once I had the regulator out I noticed there was a dimple (sign of trying to reduce regulator under pressure). I ended up replacing the FX Regulator with a HUMA regulator. It cost $115, but should prove more durable as HUMA does not use Delrin like FX and even included little spacers in case you make the mistake of reducing while under pressure. 

I second what Saltlake said, that inner o-ring in the regulator housing is brutal to replace. 

If the air is leaking out the vent hole, it's a regulator O-Ring. It can easily be rebuilt, but it requires patience. Rebuilding the regulator is considered the most technically difficult part of the gun. That said, if I can do it, so can you!

Find the FX Master Class videos on YouTube, watch them all, including the ones you won't be using. You'll pick up tips from Ernest along the way that will prove invaluable.

Find the AoA regulator maintenance video. AoA uses a different technique to remove the regulator that is easier and a different technique to install the regulator, installing the washers after inserting the post. That worked better for me.

If you have a lathe, making Ernest's little insertion tool is a big help.

Buy a set of plastic picks for inserting the housing O-Ring. They won't scratch the housing and are easy to trim and cut to better handle the O-Ring. I will tell you though, it took almost an hour for me to replace the housing O-Ring the first time. Second and Third tries were considerably faster, but be patient on that one.

You'll need to use metal picks for the O-Ring removal, just be careful not to scratch anything.

Buying O_rings from the Oring store is a whole lot cheaper than from FX or buying kits on eBay. You can buy 25 or 50 of each and save $$ overt the $40 kits.

A replacement regulator from FX is about $45, or go with a Huma. The main difference is that the Huma has a little delrin puck that protects the end of the post. If you decrease pressure, you only ruin the puck. You can turn it over and use the other side, and they give you two pucks if I remember correctly.

It all sounds complex, but watch Ernest do the replacement and the AoA video and you'll be good to go. Plan on a couple hours working on it.

Just for chuckles, consider this.

The regulator in the Impact has 5 O-Rings in 4 sizes including the housing O-Ring. My other gun, a Marauder has something like 6 O-Rings inside the gun (not including barrel bands and such) total, and only something like 3 sizes for the whole gun. The Impact is in a whole different league,

huma reg is a easy install

I have nicked orings not good