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Inlet valves & PCV

david4451

Well-Known Member
Joined
February 9, 2015
Messages
309
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City, State
cotabato philippines
Year, Model & Trim Level
2001 ford sport trac
I've started to dismantle & overhaul my 4l sohc. Something I was surprised about was the large build up of carbon on the inlet valves. The exhaust valves in were much better condition!

I'm assuming this is due to oil vapour being drawn into the inlet manifold & "crystallising" on top of the inlet valve. When previously cleaning the inlet manifold I did notice how black it was with oil.

Has anyone else found this? Is there a technical reason for this oil vapour comming from the PCV valve. Also the egr supplies "dirty" gases into the inlet manifold, this I'd expect to have a minor effect on valve condition. I'm thinking of fitting a small oil/ air separator in the PCV line anyone done this before?
 






Maybe the crud is actually egr related?
Your right though, between egr, pcv, and valve guide/valve guide seal issues you will see this symptom.

Was your motor burning quite a bit of oil? The oil vapor of the blow by past the rings and ultimately up thru the pcv valve to the intake will cause lots of oil in the intake.

Lots of people use oil separators. I'm sure there's threads on this in this forum.
 






Actually my ST was in good running condition and used no oil between oil changes.

I'm doing the timing chains and as it's a major job I decided to do a complete overhaul. I'm 67 and if I leave this work for later I fear I'll be too old to perform the task! Living in the Philippines (Brit) makes preventive maintenance essential as I don't have access to pick and pulls or reman engines.

I'll look for threads re oil/air separators. So far I've only taken the head off bank one and the worst inlet valve gunge was on cylinder 1, cylinder 2 less gunge and cylinder 3 was much less gunge. That is what made me think the PCV valve was the source of oil air mist, gunging up the inlet manifold & inlet valves.
 






I took the plastic tube off between PCV valve and inlet manifold, hung it up and was watching oil drip out of it. This oil is what's causing fouling on valves, plus making inlet manifold internally black and oily.

I used a diesel fuel filter and it's mounting bracket to make my oil separator/ catch can. I poked some holes in filter element so air flow was unrestricted. It has no effect on vacuum which is 0.7 bar or 20.7 inch of mercury same as before fitting.

This is a few photos of 'The Dude'.
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