Manifold Seal Material

[dgallup]

We are reverse engineering an o-ring type seal that will primarily see intake vacuum. Based on specific gravity & soak tests in ASTM reference fuel C we can be pretty sure they are not nitrile, hydrogenated nitrile, fluorocarbon or fluorosilicone. Temperature resistance tests indicate they may be silicone. Most of my experience is with fuels systems & we would never use silicone. Parker rates silicone a 4 (unsatisfactory) for any exposure to gasoline, isooctane, h-heptane, motor oil, transmission fluid, etc. In it's favor, silicone does have good temperature & ozone capability. Is silicone typically used for intake applications that may see some indirect hydrocarbon exposure?

 

[patprimmer]

There are special petrol resistant and Jet fuel resistant grades of Silicone rubber.

The major Silicone suppliers like Dow, GE, Wacker should be able to advise

Regards

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[dgallup]

The "good" grade of silicone rubber for fuels applications is FVMQ which the OE definitely did not use based on specific gravity. The 72 hr in ASTM reference fuel C 210% swell matches up with VMQ pretty well. I would not consider this acceptable but apparently domestic car makers do?