Calling Pat...Yanmar 2gm20F

[Chief Engineer]

I have a 2gm20f with a curious problem....the aftmost pushrod is intermittent....could this be a stuck lifter? Or would you think it may be a sticking valve? It figures that it is one of the coldest days of the year here, I maybe be suffering from "brain-freeze"

[Chief Engineer]

HElllloooooooo!!!!!!!!!!!!!!!!!!

[never monday]

Sorry, I was working yesterday.

Can't be the lifter they are solid. What do you mean by intermittent?

[Chief Engineer]

Some times it pushed sometimes it didn't.

If I put some light downward pressure on the pushrod it pushes.

Since the lifters are solid do you think a bent or sticking valve could be the culprit?

What I am trying to do is eliminate the cam/lifter out of the equation.

You and I sound like the kind of wrenches that want to narrow down the problem before possibly a needless complete tear down of engines.

Let me know what you think....I am off to deliver a boat to Annapolis

[never monday]

wow...I'm at a loss

[Artful Dodger]

I would suggest you pull the push rod and check it, will the engine run at all, if so what is the rocker action

[Chief Engineer]

Just an update....Set the valves to proper clearance.....Did compression test......way low........did notice a hissing sound when slowly turning engine over (by hand)while tester was in aft cylinder........sound seemed to come from front hole.......Rigged up a leakdown adaptor.....with cyl #2 @TDC you could hear air from #1 cylinder.

I will pull the head tom or thurs......I figger it is valves.

[never monday]

how is air transferring between the cylinders?

[Chief Engineer]

Until I get it apart, I am thinking via the exhaust valve on #2 leaking and the sound from #1 is an open exhaust valve.

Does that sound plausible?

The sound does not emanate from the intake manifold side.

So what I am thinking is, since I am going to pull the head, when I disconnect the exhaust mainfold I will perform the test again to satisfy my curiosity.

[never monday]

it's plausible
can't wait to hear what you find.

[Chief Engineer]

Plausible/Busted/Confirmed........We sound like the Boat-Mythbusters HAR HAR HAR

[Chief Engineer]

Pulled the head yesterday...waiting for shp to tell me how the valves/valve seats look. Couldn't see any headgasket failure per se, but the head gasket seemed to be delaminated....