Sep 21, 2015, 03:49 PM
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XJ Ask the Question Thread
::CF Moderator::
Joined: Aug 2011
Posts: 43,971
Likes: 1,578
From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
CF Veteran
Joined: Jan 2013
Posts: 19,219
Likes: 45
From: west chester, pa
Year: 1999
Engine: 4.0
::CF Moderator::
Joined: Aug 2011
Posts: 43,971
Likes: 1,578
From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
So I used a borescope to inspect the number one cylinder on my 4.0.
-the quench chamber/ head gasket area. (I don't know if that's the proper term for it) it's looking crusty yellow. Is that normal?
-the gap around the piston and the cylinder wall is not the same. There's a spot on the piston that got bigger gap than the rest of the piston and that gap have yellow stuff on it.
-the dish on the piston look gray and brown with a spot that look like when you get a sun burn and your skin start peeling off. There's also a line on it. Not sure if that's normal or it's a crack.
-one of the valves look very yellow/white while the other valve look very brown.
-I don't see any visible scoring marks on the wall but I did notice very very faint black line, not sure if that's a scoring mark or just a carbon smear.
-the quench chamber/ head gasket area. (I don't know if that's the proper term for it) it's looking crusty yellow. Is that normal?
-the gap around the piston and the cylinder wall is not the same. There's a spot on the piston that got bigger gap than the rest of the piston and that gap have yellow stuff on it.
-the dish on the piston look gray and brown with a spot that look like when you get a sun burn and your skin start peeling off. There's also a line on it. Not sure if that's normal or it's a crack.
-one of the valves look very yellow/white while the other valve look very brown.
-I don't see any visible scoring marks on the wall but I did notice very very faint black line, not sure if that's a scoring mark or just a carbon smear.
See if others look the same so we have a baseline to work with.
Valves are generally different color.
Black line is probably carbon.
Pistons are not smooth on top and have casting lines.
The piston won't always be centered since it's gloating on the rings.
The yellow could be today's gasoline.
CF Veteran
Joined: Jan 2013
Posts: 19,219
Likes: 45
From: west chester, pa
Year: 1999
Engine: 4.0
What's your concern with that cylinder? See if others look the same so we have a baseline to work with. Valves are generally different color. Black line is probably carbon. Pistons are not smooth on top and have casting lines. The piston won't always be centered since it's gloating on the rings. The yellow could be today's gasoline.
Good idea I ll check the other cylinders. My concern about the yellow stuff was that it could be antifreeze?
Moderator of Jeeps
Joined: Jul 2011
Posts: 21,029
Likes: 3
From: Frederick, MD from Cleveland, OH
Year: 1993 YJ Wrangler
Engine: 4.0 I6
Member
Joined: Feb 2016
Posts: 211
Likes: 2
From: Tucson, AZ
Year: 1999
Model: Cherokee
Engine: 4.0L
::CF Moderator::
Joined: Aug 2011
Posts: 43,971
Likes: 1,578
From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
the cylinder one has been misfiring ever since I got it. I checked the compression and this one is about 30-35 psi less than the rest of the engine. I determined that it's either the head gasket or bad rings based on the fact that the compression shot up after I added ATF to the cylinder.
Good idea I ll check the other cylinders. My concern about the yellow stuff was that it could be antifreeze?
Good idea I ll check the other cylinders. My concern about the yellow stuff was that it could be antifreeze?
Could have carbon under a valve.......
remember this?
CF Veteran
Joined: Jan 2013
Posts: 19,219
Likes: 45
From: west chester, pa
Year: 1999
Engine: 4.0
::CF Moderator::
Joined: Aug 2011
Posts: 43,971
Likes: 1,578
From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
CF Veteran
Joined: Jan 2013
Posts: 19,219
Likes: 45
From: west chester, pa
Year: 1999
Engine: 4.0
They are in amazingly clean condition with zero crusty yellow stuff. Hell the top of the pistons are so clean without any scale... Unlike the first cylinder.
Last edited by XJwonders; Jun 5, 2016 at 07:07 PM.