I used "eat" as a figurative term. Age, oxidation, and exposure to
deleterious compounds are the main causes of o-ring and seal failure
(breakdown of polymer chains). Technically, these parts don't "fail" they
simply suffer from breakdown of the polymer chains. This leads to the
part to fail to function as designed, but the part does not fail. Again,
we are splitting hairs, between theory, science, and what happens in spite
of theory and science.
At 03:47 PM 4/7/2006, you wrote:
Fuel doesn't "EAT" most seals. Older (those used at least thru the mid
'80s) seals swell when fuel with sulfur is used and when that fuel is
replaced with fuel that doesn't have sulfur in it, the seals shrink back
toward their original size. BUT, if they are 10+ years old, they are
likely to crack/leak. Blame whatever you'd like, but it's the age and
condition of the seals, NOT the low sulfur fuel that's the problem. Most
injection pump delivery valve "O" rings don't fail, but SOME will (only
one of the 7 OM60x injection pumps I've owned have leaked - even fewer
OM61x pumps seem to leak). I think it depends on how much contact the
"O" ring seals have with the fuel - some really have minimal or NO
contact as the metal/metal surfaces form a complete seal so the "O" ring
never has any contact with the sulfur in the fuel. In other cases, the
"O" rings are bathed in fuel and when the sulfur is removed, they shrink
and leak. The "O" rings that have been available for more than a decade
don't seem to have this problem.
There were similar problems that occurred when engines run on older
conventional oil blends were changed to synthetic oil. Mobil solved the
problem by adding some group V oil that compensated for the removal of
the seal swelling properties of the older conventional oil. That's why
changing to Mobil 1 oil USUALLY results in slight to modest oil seal
leaks being slowed or cured.
Marshall
--
Marshall Booth (who doesn't respond to unsigned questions)
"der Dieseling Doktor" [EMAIL PROTECTED]
'87 300TD 182Kmi, '85 190D 2.0 161Kmi, '87 190D 2.5 turbo 237kmi, '84
190D 2.2 229Kmi (retired)
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