Interesting tip on the 5900. I pulled the tech specs on that and it's RTV silicone with "heavy body". It's specially formulated to retain flexibility after curing.

From reading the spec sheets of a few RTVs and Hylomar they all seem like total overkill for the application, maintaining flexibility and stability over months at 500 deg f, and several hundred PSI and oil/fuel/coolant.

I wonder if there's anybody out there who has done a diligent job cleaning up the mating surfaces and had a leak within two years. Anybody have a leak to mention that was caused by the sealant?

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89 300te 222,222
92 300e 190,000