Leak down test failed :(

[gofast63]

Hey guys, I need your help on this. I did a leak down test on all of my cylinders and cylinders 1-3 are leaking 2% along with being able to hear air escaping the dip stick and a Faint sound from the intake valve. Now as for cylinder 4, it's leaking through the intake, burning oil, and has a 10-12% leak. Also while doing the leak-down on cylinder 4 air comes up through cylinder 3. Which that makes me think the bottom ring isn't sealing on #3. This is a rebuilt motor done by me. Valves have been lapped. I'm starting to regret not having the cylinders honed. Not sure what to do. I've been dying to drive this piece of for years.

 

[Calan]

Did you pop the rockers to make sure the valves are fully closed?

 

[gofast63]

No, I didn't even think of that. I'm going to do that now.

 

[gofast63]

I popped the rockers off of cylinder 4 (just the intake rockers.) and I still got the same results. I can plug my thumb in cylinder 3 and more air will escape through the intake valves.

 

[Calan]

If you are injecting air into #4 and you are sure all valves are 100% closed on #3 and #4, and you are getting a lot of air from the plug hole of #3, then

1). You have leaking rings on both cylinders
2). You have leaking valves on both cylinders (in which case you would hear it in the intake or exhaust, more than #3)
3). You have a break in the head gasket, or it isn't sealing properly between #3 and #4

If air is moving between the cylinders but not out the exhaust or intake, it's probably the head gasket.

Some air past the rings is normal (especially if the engine is cool)... as long as compression is still good.

 

[gofast63]

Hey Calan, I took the rockers off of cylinder 3 and doesn't leak anymore. I should have done that in the first place. But I didn't think it would cause the leak. Cylinder 4 is the only one that's leaking. It's coming right out of my intake elbow.

 

[Calan]

Cylinder 4 is the only one that's leaking. It's coming right out of my intake elbow.

If it's doing that with all the other intake valves completely closed, then you have leaking intake valves on #4.

It's also possible that air is going past the number 4 rings and into the crankcase, then back up and past the rings in another cylinder and out it's valves....but it isn't likely. Remember air always takes the path of least resistance; follow that path, and you'll find the leak.

 

[gofast63]

Awesome . Seriously didn't want to pull the engine out again. You think I can get away with lapping them again? Also is a faint leak in the intake valves normal when you you perform the leak down test?

 

[Calan]

I have no idea. Without being there, I don't know how big the leak is or if what you are experiencing is extreme or just a minor issue.

Try it and see.

Some leakage past the rings and into the CC is normal, but not past the valves if they are closed.

 

[gofast63]

Yeah that was kind of a dumb question. (still kind of in panic mode) . I'm going to post a video of the leak down test.

 

[gofast63]

When I do the leak down test am I suppose to plug the nipple on the valve cover.? The one the the left side when you are standing in front of it. Cause that is leaking air as well.

 

[Greedy Pimp]

No don't plug it. It's leaking air that is being pushed past your piston rings.

 

[gofast63]

No don't plug it. It's leaking air that is being pushed past your piston rings.

Valves were open on cylinder three. I popped the rockers and it went away. I have the head off now and I'm going to get to work on it in the morning.