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Re: Crankcase venting question Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Tue, 26 Aug 2008 18:53:13
In Reply to: Re: Crankcase venting question, Kevin M  [Profile/Gallery]
, Tue, 26 Aug 2008 18:38:04
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Actually, you'll get negative pressure in the crankcase at all manifold pressures less than atmospheric or so. Once the turbo kicks in and the manifold pressure goes above (absolute) atmospheric, the one-way valve should close.
Two common problems with the one-way valve in the line - (1) it is broken, or (2) it's in backwards. If it's broken, it's not blocking turbo pressure, and you'll be pressurizing the crank (and pushing oil past the valve seals). If it's in backwards, same thing.
So make sure the valve is truly one way, and one way in the right direction.
Frankly, I think you've got bad valve seals. At idle, you've got high vacuum in the intake, and the turbo isn't in the picture. It doesn't matter what the crank ventilation is doing. But that high vacuum tends to suck oil through the valve seals.
The classic test for this is to find a nice, long downhill. Get the car to speed, and take your foot off the gas. If you see smoke, it's usually valve seals. The engine is at high rpm, but the throttle plate is closed, so the engine is nothing but a big pump, running fast, sucking against a blockage. That's the highest vacuum the intake will ever see, and the greatest strain on the valve guides.
If it were a turbo pressurization issue, I'd expect the issue at high boost. Of course, it would be difficult to tell if it were turbo bearings.
posted by 192.249.4...
, Tue, 26 Aug 2008 16:45:34, Mon, 8 Sep 2008 12:51:46, Thu, 28 Aug 2008 16:37:24, Fri, 29 Aug 2008 08:44:46, Tue, 26 Aug 2008 18:39:46, Mon, 8 Sep 2008 12:27:02, Tue, 26 Aug 2008 18:38:04, Tue, 26 Aug 2008 18:53:13 <-- Viewing This Message, Tue, 26 Aug 2008 19:33:22, Wed, 27 Aug 2008 10:38:55, Wed, 27 Aug 2008 15:56:44, Thu, 28 Aug 2008 10:01:00
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