Hissing while rotating engine with ratchet.

[masterelyt]

I'm tearing down my 2.9L engine from my 88 BII because it was ticking and had some other weird noises while running. After getting one of the valve covers off I decided to rotate the engine with a ratchet and I'm noticing a few things...

-Hissing coming from the cylinder head

-Resistance isn't consistant through the rotation (I know how an engine should feel and it seems like it's much easier to rotate in certain parts of the firing cycle)

Anyone know what this might mean?

-Tyler

 

[adsm08]

Sounds perfectly normal to me.

Hissing is compression slowly escaping through a partially open valve since they don't always stop dead on closed.

The resistance changing is normal as well. Some parts are easier because you aren't always fighting compression. When the cylinder that is on it's compression stroke is just coming up and the cam lobes aren't pushing valves at the tip of the lobe yet it will be easier to spin. I have spun hundreds of engine rotations by hand and many different engines, both gas and diesel. Can't think of a single one that didn't have spots that were noticeably harder to get through.

 

[masterelyt]

Okay so it doesn't necessarily indicate a cracked head? I've been told that's an extremely common problem with these engines!

 

[Sunk]

Ticking is also extremely common on 2.9s and considered normal. It'd be abnormal if yours didn't tick.

 

[masterelyt]

I've never heard a ticking 2.9L as bad as mine.... you can hear it blocks away and it sounds like the damn thing is getting no oil at all also it makes some weird grinding, rattling sounds when I rev it up, I'm thinking those noises are linked to a deeper issue than a mere lifter tick.

 

[birddog321]

Much deeper