CurtPalme.com Home Theater Forum

redfox001 · Joined: 16 Mar 2009 Posts: 2257 Location: The Netherlands

Hi Guys I did this experiment some months ago. In the bottle with glycol there are both old and new screws with washers only. the rubber on the washers clearly colours the glycol after some time.

So no need to blame the bellows.

Untitled by Radio Head, on Flickr

redfox001 · Joined: 16 Mar 2009 Posts: 2257 Location: The Netherlands

IMG_2023 by Radio Head, on Flickr

Old and new washers.

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

The new screws are stainless steel. Not blackened steel.

The black iron oxide coating on the older style screws is believed to be at least one cause of discoloration of the coolant.

Another is believed to be related to the interaction of coolant with the aluminum front piece, even though it is protected by a layer of hardcoat anodizing. Which, it must be noted, is NOT a chemically inert coating. Anodizing requires sulfuric acid and anyone who has ever cut, scrape, ground, or sanded anodized parts knows the sulfuric smell they give off when you do that. A small amount of sulfuric acid is trapped in the anodized layer and it is likely that it interacts with the glycol.

Interestingly, the LC assemblies of G90s never get discolored coolant.

And there is no aluminum in the G90 LC assembly, not in any part that is in contact with coolant.

**Curt Palme** · Posted: Sun Jul 10, 2016 7:57 pm Post subject:

Yes, I found that out a year or so ago and posted about it. Once those washers get soft, it kills the glycol. Make sure to clean out the threads as well, as a tiny bit of rubber is always left in there.

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

I recommend a THIN layer of silicone is applied to the underside of the sealing washer right before installation. Not enough to make a mess, just a little bit to coat the rubber gasket and it also will help in forming a complete seal.

I think there's probably a better washer to be used than the one found on the fill screws. Maybe Apple Rubber, the company that makes Nashou's bellows, would be able to punch out a batch for us at minimal cost, made of the same propylene-ethylene rubber as the bellows?

**Curt Palme** · Posted: Mon Jul 11, 2016 12:08 am Post subject:

I'm sure something else is out there, but with a typical 10+ year life, why not just change out the rubber washers every 10 years to be safe?

Tim in Phoenix · Joined: 21 Oct 2006 Posts: 4409 Location: Phoenix

Guys

I'm thinking it's corrosion from the steel screws. I never suspected the rubber washers.

redfox001 · Joined: 16 Mar 2009 Posts: 2257 Location: The Netherlands

I will try to narrow it down a bit more the next months just for fun Smile

I think I conclude that the bellows are now less likely to cause the coloration in my tube. However I did put in new screws and washers but perhaps the cleaning of the holes was the problem. To be sure I will test the new washers separate.