O-320 making a clicking noise

I have a O-320-E2D in a 150 (yes, I know a spam can question on a RV site) of mine that has a noise we can't seem to figure out. It is a mid time engine with about 300 STOH. It has started making a clicking sound that you can clearly hear while running. It's not a knock more of a loud click.

The engine is not making any metal and all the compression is good. At first we thought it was a lifter not pumping up or something since it tents to get a tad quieter when the engine warms up. We pulled all the rocker box covers and the valve "lash" is good and we didn't see a valve sticking. When you pull the prop thru by hand you can hear the click and it seems to be comming from the front pilots side cylinder (I forget what # that is) on the copression stroke. Funny thing is if you pull the prop back (Backwards) from the compression stroke it clicks too. When we pulled the spark plug the noise goes away. I've had several people listen to it and they are stumped. I had one IA who suggested it could be a hung up wrist pin and the noise is comming from the little keepers or plugs moving back and forth.

Before I pull a jug I was wondering if anyone on here might have a suggestion. The engine did a tid bit of sitting for a few months last year so that could be a contributing factor.

Thanks!

Mag?

Have an impulse coupled mag? Vacuum pump getting ready to go? Baffles cracked and loose somewhere? Alternator bearings worn? Engine mounts OK? Lots of possibilities. TOO many.

Maybe piston slap. Listen to each cylinder with the engine running with a stethoscope or a long screwdriver with the handle at you ear and the blade on the cylinders. You should be able to see which cylinder is making the noise. Take it off and investigate.
Good Luck,
Mahlon
"The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at your own risk."

stethoscope

We tried listening to it using a stethoscope but not while it is running. It's hard to pinpoint the noise but it definatly not comming from the acessory case. It's not the impulse mag (it does have one and it sounds close to that). The baffles look good i'll look into the vacume pump too.

I should have added that if you hold your hand on the case you cans actually feel it click. some where in the cylinder area. Also it seems to make the sound in one of the other cylinders too.

Hi Bruce,

I don't have an answer to your question but I know where there is a big bunch of Cessna experts and A&Ps that hang out and answer correctly just about anything that comes up. Might be worth a post at:

http://www.cessna-pilots.com/howto_signup.html

I've had some very complicated questions on my 182 answered there.

Cheers,
Dave

Cessna pilots

Dave,

Thanks for the tip I'll check that out. I think I'm just going to have to pull a jug just to be safe. The sound seems to be comming from the barrel. The strange part is how it goes away with the plug out.

I had this happen on a 4 Cyl. Nissan truck engine once. The thing even passed emissions.

The cause... Get this...

It was a loose spark plug and the clicking was the sound of the air moving past the plug. After it was torqued to spec, the noise went away.

Check both plugs, you might get lucky.

clicking noise

I have an 320D2J that makes the same identical noise under the same circumstances I was wondering if you ever got anything figured out