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Here's the PCV deal (long post, dramatic ending) Posted by Cmyles [Email]  (#1126) [Profile/Gallery]
(more from Cmyles) on Sun, 14 Mar 2010 10:28:46
In Reply to: Re: PCV, Simon S, Sat, 13 Mar 2010 13:54:33 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Simon S,
The PCV system wants to move gas (blow-by air and fuel mix) not vaporized engine oil so there is a supply hose and a vacuum hose. At idle manifold vacuum is high and blow-by is low. Under those conditions air moves, under the influence of manifold vacuum, from the air filter* to the intake manifold by way of the valve cover (crankcase). That flowing air collects the blow-by from the crankcase on it's way to the manifold. If the air supply hose is restricted then the manifold vacuum draws oil laden crankcase vapors in and burns them along with any blow-by gas. As the engine RPMs increase manifold vacuum falls off, blow-by increases and those oil vapors aren't drawn in and burned. When the manifold is pressurized by the turbo the check valve closes (so as not to pressurize the crankcase) and crankcase blow-by pressure is then relieved through the large heated hose. This problem is commonly seen on older vehicles when the PCV hoses are in bad shape and I've seen it mostly on vehicles that had no turbocharger.
*The large heated hose that goes from the black plastic Y port in the valve cover to the hole in the "turbo to throttle body pipe" is the PCV "supply hose", except under boost.
Of course other things will cause oil burning; bad rings, turbo problems, failed head gasket, but those will usually produce other symptoms and conditions and aren't generally confined to idle only. Pam says that when she disconnects the large hose from the valve cover the smoking at idle stops. Disconnecting that hose either provides a fresh air source for the crankcase so manifold vacuum isn't applied to a "sealed oil container" or the source of the burning oil is being disconnected. The former supports my "PCV system fault" diagnosis and the latter implies that oil is entering the "turbo to throttle body pipe" and being drawn through the valve cover and on to the manifold. Faulty turbo seals don't do that at idle only. And they all lived happily ever-after. The end.
posted by 198.233....
, Sat, 13 Mar 2010 11:20:44, Sun, 14 Mar 2010 10:28:46 <-- Viewing This Message, Mon, 15 Mar 2010 10:59:54, Sun, 14 Mar 2010 11:14:54, Sun, 14 Mar 2010 11:35:57, Sun, 14 Mar 2010 11:37:37, Sat, 13 Mar 2010 17:27:38, Sat, 13 Mar 2010 10:16:27
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