Tapping noise from valve and side cover

[ninob]

I was adjusting my timing yesterday, and noticed a tapping
sound coming from the valve cover. Can anybody give me some
Ideas of to what might be the cause of this. Engine is 96 mercruiser
3.0lx

 

[fixb52s]

Re: Tapping noise from valve and side cover

It is either a bad lifter or maybe something as simple as an out of adjustment rocker arm.

 

[Black as]

Re: Tapping noise from valve and side cover

Same thought as the above comment but also add when was the last time you did and oil and filter change.

 

[ninob]

Re: Tapping noise from valve and side cover

I changed the oil and filter recently, I removed the cover and I think
I have a bent push rod. I'm guessing this
would cause that.

 

[Black as]

Re: Tapping noise from valve and side cover

That would cause a tappet noise and an easy fix as well.

 

[ninob]

Re: Tapping noise from valve and side cover

Seems like bent rods, I was consern that it might be rod bearings.
Hope it goes away once I change them. Would having bent rods cause
rough idel aswell?

 

[Friscoboater]

Re: Tapping noise from valve and side cover

Another cause would be a cam that has a flat lobe or two on it.

 

[oops!]

Re: Tapping noise from valve and side cover

yes it would. but you should find the cause of the bent rod

 

[Black as]

Re: Tapping noise from valve and side cover

Seems like bent rods, I was consern that it might be rod bearings.
Hope it goes away once I change them. Would having bent rods cause
rough idel aswell?

Yes it would cause rough idling

 

[ninob]

Re: Tapping noise from valve and side cover

I bought the boat like that, I think the previous owner might have over reved it at one point, Im guessing that would cause a rod to bend.

 

[Bondo]

Re: Tapping noise from valve and side cover

Ayuh,... Probably the Most common reason for a bent pushrod is rusting of the valves...
The valve rusts, Tight,+ the pushrod gets bent pushing it open...

 

[fixb52s]

Re: Tapping noise from valve and side cover

The pushrod could have been bent by an over rev condition, or adjusted too tight. The only hope here is the valve didn't float and possibly strike the piston.

Best thing to do is hand crank the engine over with the cover off and look at the lifters. See if they all are moving the same. A bad lobe on the cam will not allow that one lifter to raise the same as the others. Also check the conditions of all the pushrods by rolling them on a piece of glass. If one is bent due to an over rev, then you just might find more. If all looks fine, replace the pushrod and adjust the valvetrain by the book. After doing this, run a compression check to see the health of the cylinder. Doing a compression check before replacing it will not yield an accurate reading.

And as stated before, this certainly will cause a bad idle.

Edit: Just seen Bond-o's post about the rusted valves. Never thought of that, but sounds reasonable. Easy to check with a different rod installed. Turn the engine over by hand and see if it might hang up when that valve is actuated.