I sealed one of my leaking EHAs with POR-15 and it has held for 2.5 years. The other leaking one I replaced with a parts car EHA which did not leak.

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W108M117(1972) repaired after deer hit
W124M103(1987)
W124M103(1989) -- sold to son's friend
W124M119(1993) --
W124M103(1987 -- 5 speed Euro) - sold to forum member
W124M103(1989) -- TE
W123OM616(1977)
W201M103(1990) parts car