Date: 2 Jun 2005 15:51:30 GMT From: Dave Hinz <DaveHinznospamcop.net> Subject: Re: warranty
On Thu, 02 Jun 2005 11:08:00 -0400, Malt_Hound <Malt_Houndnospamm*yahoo.com> wrote: > I agree, this explanation of the sludging problem is somewhat lacking. > Regardless of the design of the pistons and rings, there is no raw fuel > in the combustion chamber to seep down into the crankcase, *unless* you > also have a fuel injector leakage problem. Yes, I'm not sure I understand how blowby of gasoline would cause sludge, however... > Even with that, I would expect thinning of the oil and excessive engine > wear, not sludge buildup. If anything, flushing the crankcase with a > bunch o fuel thinned oil would *reduce* the sludge buildup not increase it. Right. > I have heard of sludge problems on the 4 cylinder engines ever since the > recommended oil change interval was increased. I first heard about this > when I had a 2000 9-3 2.0l. OTOH, I've never heard of it occurring on > engines where the oil was changed at 5k miles religiously. I think the key, Fred, is in how the oil vapors are recovered by the PCV system. There is a, well, a box at the bottom/back of the engine that condenses the mist back into liquid, to drain back into the sump. There's a small orifice going into this box, I'm guessing to limit airflow. Problem is, that mist then gets "mistier" while hot, in an oxygenated environment. Chemicals oxidise more rapidly when they're in smaller particles, _and_ when they're hot - both conditions which occur in this particular PCV oil reclaimation method. Google for HSA (Hot side aeration). To get the homebrewing links out of there (it occurs there as well), try this string hot side aeration oil sludge -beer I'd bet a bottle of nice Scotch that this is the cause of the problem, maybe made worse by combustion byproducts blowby past the piston rings. Dave Hinz
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