Engine knock

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Godwin

Godwin

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I recently picked up a FJ 62 that has an engine knock. By pulling the plug wires I've isolated the knock to the #3 cylinder and I'm planning on dropping the pan in the next couple of weeks to have a look. I can pull bearing caps and check the bearings to see if any are obviously trashed, but otherwise how can I tell the condition of a bearing?
 
i also have a lower end knock, this may sound stupid, but how did pulling the plug wire isolate the cylinder? the crank is turning and rods moving if that cylinder is firing or not ?
 
With the engine running I went through and pulled each plug wire one-by-one. When I pulled the #3 plug wire the sound of the knock diminished and with that I knew that the source of the knock was with #3. The piston is still moving in the cylinder but with the pulling of the plug wire there is no explosive force within that cylinder and the rod end is not getting slammed as hard against the crank. At least this is the way that I see it.
 
mmireles49 said:
Splitshot, what is piston slap?
Click to expand...

The way a [small] piston engine is designed a "tilt" in the piston occurs. When the piston goes up it gets "pushed" to one side. As the piston comes down it gets pushed to the other side. Thus "piston slap".

It is caused by secondary (sideways or perpendicular) movement of the piston against the side of the cylinder. All piston driven engines as wells as compressors have a certain amount of piston slap.
In large [ship] engines there is a second connection called crosshead (http://en.wikipedia.org/wiki/Crosshead) as the forces get so large they could ruin the engine in a short time.

Over time with wear and tear it starts to make a sound particular when cold. As the engine heats up and all fits tighter the noise fades. If it remains the engine is usually old and worn, due for a rebuild.

Damit!:bang: Google it!

Piston slap, piston slap sound, piston slap cause
 
Godwin said:
With the engine running I went through and pulled each plug wire one-by-one. When I pulled the #3 plug wire the sound of the knock diminished and with that I knew that the source of the knock was with #3. The piston is still moving in the cylinder but with the pulling of the plug wire there is no explosive force within that cylinder and the rod end is not getting slammed as hard against the crank. At least this is the way that I see it.
Click to expand...

makes sense.. thanks, i need to try that on mine
 
Plan for the day was to crack it open and check the bearings. I picked up plastigage, oil pan gasket, and some FIPG. This engine has been worked on in the past and the oil pan is glued on with silicone; no gasket was used. I tried to break it loose but can't get a good angle on the pan and I'm not that motivated. This FJ62 was purchased to serve as a parts rig to do a 2FE conversion on my 60 and I don't want to put too much time or $$ into the 62. With a little cash and time it can be driveable and my kids can use it locally until something major breaks. I ain't gonna worry about it :hillbilly:.

Also replaced the valve cover gasket and grommets this weekend curing a vacuum leak, plus adjusted the valves. What I noticed after this is that when the engine is cold the knock is noticeable and diminishes some once the engine is warmed.
 
I found that lots of heat was the ticket for getting the pan off.

But yeah, it's a TOTAL pain in the butt. Dunno why it has to be on there
so tight- the darned things seem to leak anyways...

A knock that dimishes as the engine warms is often piston slap- rod knocks usually
get worse as the oil heats and thins...

I spent $8 on one of those stethoscopes with a rod on the end- it found my flat cam
in about 10 minutes of listening around and unhooking things....

t
 
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