SNIP<

You need to do accurate calcs on the cross sectional areas and avoid
sealant, altho this may just extrude out of the cracks when heated.  The
rubber is too strong to easily extrude thru the fine cracks (near zero

crack

width) and can crack something if fully trapped.

Bill Freeman

I always encourage experimentation when there is something to be gained but
when it comes to sealant for Mazda coolant O-rings, the experiments have
already been done.  Use ONLY Hylomar non hardening sealant.

Tracy Crook
tcrook@rotaryaviation.com
www.rotaryaviation.com

I have always thought of rubber, and that includes silicone, as being
"compressible". What has been brought home to me  after reading Tom's
experience is; rubber is no more "compressible" than hydraulic fluid.

Bill hit the nail on the head I think. The O-ring was oversize for the
slot and in the process of tightening down the tension bolts the hydraulic
force of the rubber broke the housing.

Bottom line is measure the O-rings you get and don't use
anything larger than .093" diameter in the outer slot. As Tracy points
out don't use RTV to hold the rings in place as it could harden
and add to your problems. Buy the O-rings slightly under size on the big 
diameter (no more than 5% undersize) and stretch them on a plywood form for a 
few days before installing them. They will then lie in the slot perfectly as 
we discovered with Perry's installation. Don't try to stretch the ring 
by hand or by another method as you could permanently neck them down.
Be careful when buying standard 3/32 O-rings sizes as they may be larger
in section diameter than .096. They could be as large as .115 or so which
is way too large for the outer slot. Apparently standard 3/32 rings 
work OK in the larger inner slot. 

Best to buy the O-rings directly from Creavey the manufacturer.
In most case the prices are lower than what Mazda charges for lower
temp stock O-rings.

Here is a part of their catalog again showing the small increments in 
section diameter that they sell.
http://www.creavey.com/

Paul Lamar
 
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