Pitted MK10 Ambient Chamber

[Treculi]

While waiting on a kit and a couple of tools I started dissembling and cleaning my MK10. When I started cleaning the ambient chamber I discovered pitting on the wall. There appeared to be some scoring but the piston head and shaft were clean with no marks or signs of wear. The o-ring (gray) looked worn but intact. There was some very small debris but not a lot. Can anyone tell from the photo if it is beyond repair?

Thinking back I had injected silicone into the chamber for ice diving in fresh-water. Later on I made a couple of saltwater dives without removing the silicone. I am wondering if the silicone prevented a clean rinsing and trapped saltwater in the chamber.

 

[redacted]

It may be the picture, but I don't see anything there I would be concerned about on the area where the piston will have to seal. Rebuild it and see if it leaks. I have had some that had most of the chrome missing and deposits on the brass surface. A good cleaning and a little touch up with brasso and all worked fine.

 

[halocline]

Thinking back I had injected silicone into the chamber for ice diving in fresh-water. Later on I made a couple of saltwater dives without removing the silicone. I am wondering if the silicone prevented a clean rinsing and trapped saltwater in the chamber.

It's likely that's what happened. You have to be really careful when packing the chamber to make sure there are no voids. I don't think it's possible to do that unless the piston is out when you pack it.

But, as awap says, it doesn't look like anything is too bad in your photo. If it leaks or tears up your piston head o-ring, you could try polishing out the pits with micromesh. It might work, but it would take a lot of elbow grease.

 

[Treculi]

Thanks. I plan on putting it back together one way or another. The DIY forum has been a great resource to get started. Here is another photo.

 

[Treculi]

I thought about cleaning the chamber with Brasso and/or Microscreen as suggested and came up with a hybrid idea. I had a soft buffing wheel for a Dremel tool that was a little larger diameter than the chamber. I had some ferrous metal buffing compound and ran it through the chamber for about 30 seconds. It cleaned a lot grim and a few pits off the walls. I picked up some Chrome buffing compound today and ran it through for about a 30 seconds. Below is a before and after image.

 

[halocline]

Looks great!

 

[Zung]

Good job!

I have one where a few (small) spots are won to the brass. After some brasso'ing, its works like a charm.
Another one has the chrome inside entirely stripped. It still sealed, but after a year or so in a closet, the Christo-Lube turned green because of the verdigris. It looked ugly, so I replaced the cap.

Edit - Actually, mines are MK20.

 

[Treculi]

Good job!

I have one where a few (small) spots are won to the brass. After some brasso'ing, its works like a charm.
Another one has the chrome inside entirely stripped. It still sealed, but after a year or so in a closet, the Christo-Lube turned green because of the verdigris. It looked ugly, so I replaced the cap.

Edit - Actually, mines are MK20.

One reason I only buffed the chamber for about 30 seconds is I did not want to chance buffing through the chrome. Everything else looks good and I am looking forward to putting it together. I am just waiting for a couple of tools to arrive. If all goes well I may look into the second stage.

 

[superstar]

I freshened up a pitted ambient chamber with a wheel cylinder ball hone similar to this. KD Tools 2480 Brake Cylinder Flex-Hone®, 7/8", 180-grit

 

[Treculi]

I freshened up a pitted ambient chamber with a wheel cylinder ball hone similar to this. KD Tools 2480 Brake Cylinder Flex-Hone®, 7/8", 180-grit

That’s interesting; I have not seen those before. When I was buffing out the chamber it reminded me of deglazing the cylinders of a 235 block underneath a porch deck during a snowstorm. Ah youth, goofy kids.