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Mitsubishi 3.0 SOHC Engine

Replacing the PCV Valve

Due to a poor design of the PCV valve system, the Mitsubishi 3.0 engine does not tend to ventilate the crankcase very well. This tends to occur for 2 reasons. First, the crankcase ventilation path flows through the ceiling of the valve covers, and area that becomes filled w/ oil and gunk and which cannot be cleaned out. Second, in part due to this, the PCV valve tends to get clogged up.

My desire to overhaul this engine came in part due to its prodigous oil leaking. Although this may be due to old worn seals, the most common reason is a clogged PCV valve.

The PCV valve sits directly on the engine block, and screws right into it (as opposed to on the valve covers, in many engines). First, locate it just to the right of the upper intake plenum.

pcv_replace1_label.jpg

In this picture, the disconnect 1/4" hose hooks directly to the valve, which is a typical cylinder-shaped metal ball valve. Remove the old one with a "deep dish" 15mm socket wrench.

Shake the old valve. If you hear a strong rattle, valve is good. If not, replace it. They are so cheap, and so important in this engine, that I would replace it anyway if I went to the trouble of removing it.

Here is a view of the new valve, with a newly cut hose. Be careful not to strip the threads where the valve goes into the engine block. A good dose of anti-seize is in order.

pcv_replace2.jpg

Easier than changing the oil. If you want to further improve the PCV ventilation, you can remove the valve covers and try to clean out the PCV vents in the top. (Note the PCV hose goes directly into the top of the valve cover in the above picture). I did this, not sure I gained very much -- although I got a nice look at the SOHC valve train !

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