silicone sheeting/air regulator diaphragm

rampeyboy · August 22, 2010, 05:08:32 PM

I've read in the archives about using silicone sheeting for replacing leaking diaphragms. What grade of silicone sheeting do you use? Medical grade, or general use? Thanks!

Boyce

zubzub · August 22, 2010, 08:27:15 PM

Nice thickish one that you get at wallmart or similar. The are baking sheets, you need nice smooth surfaces

rampeyboy · August 23, 2010, 02:11:10 AM

thanks!

kyle4501 · August 23, 2010, 04:41:16 AM

What diaphragms are you looking to replace?

rampeyboy · August 23, 2010, 04:50:57 AM

Kyle, I have that one in the tool compartment for the aux air system pressure regulator. It is I think inline with the wipers. So far, that's all I've found that is leaking badly. I'm sure though I will find more as I fix leaks here and there!

zubzub · August 23, 2010, 05:40:14 AM

I fixed that one with the silicone sheet. Dallas had a write about it somewhere. It's a good candidate as the plumbing is so tight in there and aftermarket PR would be hard to fit. BTW fixed a brake light switch that way as well. p.s. don't be using sheeting to replace brake diaphragms though!

rampeyboy · August 23, 2010, 06:43:13 AM

Thanks for the heads up zubzub! I was wondering if the silicone sheeting could be used on any diaphragm or just select ones!

Boyce

kyle4501 · August 23, 2010, 11:08:48 AM

Just tossing out a thought, but I'd think the homemade diaphragm needs to be close to the one bring replaced.If the old one has a heavy contour (like brake diaphragms), the new one needs to match or it won't function properly - if at all.

The brake can diaphragms are easily available.

rampeyboy · August 23, 2010, 03:24:55 PM

ok guys, I'm armed and dangerous as they say! I got the silicone sheet, and hope to get out tonight and remove the old diaphragm. Assuming it is the same thickness, and stretchiness as the silicone sheet, is there anything that needs doing to the silicone sheet prep wise, or can I just cut and install?

Boyce

zubzub · August 23, 2010, 05:12:51 PM

Dallas has a description on his site.
http://busconversionstuff.com/galleryBCS/thumbnails.php?album=2
I did mine a little differently. The thing is that reg is hard to get at, removing it is the hard part and i'm pretty sure it's too hard to do in situ unless you go through the floor above. My '04 has an access hole above the plumbing, so instead of working through the side door, once the seat was removed I could have replaced the diaphragm in situ. I used a little gasket sealer around the edges to help the seal.

rampeyboy · August 23, 2010, 06:05:12 PM

holy PITA! I got the old diaphragm out, but what a pain that was! The Scenic has another valve/switch of sorts immediately adjacent to the regulator which made removing it tough! Finally I got the top of the regulator off, leaving the base on the lines.

I'm glad you sent the link. I was just about to put the silicone sheet on, but it was getting dark, so I called it quits for the day. I see in the link he sandwiched the silicone between cork. What purpose is the cork? I would think that may make it more likely to leak. I'll have to pick up a roll of cork gasket material tomorrow.

Second question, dummy me failed to notice if the rounded "pin" on the diaphragm goes up or down? Looks like in his first picture the rounded pin goes towards the spring. Hmmm where did I put that manual??? Better get to reading....

rampeyboy · August 23, 2010, 06:18:25 PM

nevermind on the rounded pin question! Found it right off in the manual. The pin/screw part goes towards the mounting ears of the regulator, and the nut goes towards the spring. Parts book Pg 4-21, figure 4-1821