Originally Posted by Walt Fricke
Woody
You are, indeed, being too anal. I've never seen sludge in any of my 911s, and I am careless about maintenance.
I got my '77 (gray market car) in '84. About '87 or so I replaced the Ps and Cs. Had a good look inside doing it, no issues. About '89 it blew up (valve head fell off). Pulled the mess apart, no sludge. Got an '82, who knows its history either. About '97 pulled it apart (broken rings). Again, no sludge.
To satisfy your anal urges, though, do this: disconnect the oil inlet line at the front oil cooler. It is up high so you won't make too much of a mess. Blow compressed air through the cooler. That should force most of the oil back into the oil tank (through the filter, by the way). Those fittings are not as apt to be ruined by disassembly as the aluminum to steel fittings on the thermostat in the back. I just did something like this while changing an oil radiator (horizontal in front valance opening, so it was going to spill a lot when disconnected). Worked fine.
If you do this after you have drained the oil tank, you ought not to have a problem with oil being blown up into the air cleaner-throttle body area.
That way you will get out something more like the 12 or so quart full capacity, rather than the usual 8 or so. Which means you have to add more in (carefully, as overfilling is easy. With such a large tank, an underfill isn't really a problem if you take things easy until the oil is hot and you can measure it accurately in the tank and top off).
One thing you could do is take the old oil filter, when you change the oil and it, and cut it open (best to find someone who has a purpose made tool to do this like a can opener, so you don't get stray saw filings in there to complicate things) and look at what it caught. I bet you won't find much, and what you find may be a little bit of sort of tiny silvery stuff - as in normal metal shavings from bearings and cylinders and rings and such. If it is all clogged with copper, well you have worse issues than putative sludge with which to deal.
Oh - you can purchase an oil analysis kit, so you could save some of your old oil and have it analyzed.
But you'd be nuts (not to put too fine a point on it) to pour some stuff into your engine other than fresh oil. I think that kind of thing went out with the '20s. Sure, it sounds good - clean out the old, start fresh. But the insides of these engines are very very clean absent horrific abuse, and even poor modern oils are fairly decent. The filters catch the particulates, so all the engine innards see is nice slippery oil. The odds that previous owners never changed oil or filters, and just added the odd quart every couple of thousand miles for several hundred thousand miles, are pretty slim. And if they did that, you've got problems cleaning may well not fix.
Walt Fricke
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