Why is this hydraulic control leaking on my Ford 3000?

[gelbviehguy]

Bought this aftermarket remote setup and everything works fine,but it has a little leak out the back. See pics. All the o-rings are there and the bolts are tight. I went to take it off a minute ago and when I got all 4 bolts out it went "pop" and let some hydraulic fluid out. I thought the o-rings took the place of a gasket?

 

[ronchp]

Assuming those o-rings are new since you said it was a new setup, I guess I would inspect them with a magnifying glass to check for nicks and replace any that are defective. You may also want to clean up some of those sealing metal sealing surfaces with a little steel wool or wire brush to make sure there is no corrosion particles from giving you a good seal.