Topic: YJ: Puking Exhaust Valves ???

[JimmyFW1]

OK guys, I have my brain fart moments & then I have my moments where I actually
get my hands dirty & get things done. (This weekend was a series of the dirty
hand moments)
Got my Liberty back on the road after a minor setback. Now, back to the YJ (my
real Jeep )...

Let me catch you up to date. About 45K miles ago, the YJ crapped out on me on a
road trip from SC to FL. Had a local shop tear it down & found that I have
burned the #3 cylinder exhaust valve. Replaced the valve, put it back together &
was back on the road for $600 labor & all (not happy, but not raped as bad as I
thought I was going to be).
Last year, it did it again on a return road trip from FL back to SC. Lost all
power. Towed it home & parked it. Bought the Liberty for a DD , and let the YJ
sit.

Got ballsy over the weekend & started checking the little things. Power to the
cylinders was good (plenty of fire as I found out from an uninsulated pair or
pliers I was holding). Did the redneck compression test & found that the #2
cylinder had NO compression. Pulled the valve cover, rockers & rods, nothing
visible as the culprit yet. Pulled the head & sure enough, the #2 exhaust
cylinder is stuck open.

What would cause yet another exhaust value to go bad? in a different cylinder?

I've got no headers, no aftermarket performance upgrades. My high flow cat.
converter & Gibson exhaust is the only upgrade I've done to the engine system.
Oh, & an Accel Super Coil, but I wouldn't think that would be an issue here...

Any help would be greatly appreciated...

[sharpxmen]

question is why is it stuck open, is the valve bent or is it seized in the valve guide.
1. if bent, then check the cam timing, timing chain and sprockets. also, check the rocker, valve spring and hydraulic lifter, if a rocker or lifter is seizing during engine operation the piston will catch the valve and will bend it or even worst scenario will break and make a mess of your piston/cylinder and cylinder head

2. if seized then it's the guide, the valve or oil to that valve (less likely but it can happen) - this will also cause the valve to bend when hit by the piston btw.

so take the valve out and check the valve stem, if it's scratched then it seized in the guide, if not scratched and no signs of seizing in the guide then check the things at #1.

post pics so we can also see what you have in there, both the head, the cyl and piston with the problem and the valve itself.

[sharpxmen]

any updates? did you figure out what happened?

[Torch_Ind]

also just wondering  if you only replaced #3 cylinders valves the first time and didn't take any attention to the rest of the valves. cause your state it was #3 last run and #2 this run. 

to me it could be wear and tear and you only fixed what broke last time not rebuilt the rest.

[grumpygy]

Have to pull my head to remove a broken bolt.  Yes the back exhaust one.  Had a broken extractor in it and I broke a drill bit.  So I was watching this to see if while I had it off to just go thru the head and refreash everything.  It got 160,000 miles on it now.

[sharpxmen]

Have to pull my head to remove a broken bolt.  Yes the back exhaust one.  Had a broken extractor in it and I broke a drill bit.  So I was watching this to see if while I had it off to just go thru the head and refreash everything.  It got 160,000 miles on it now.

you probably should, i would replace the valve seals, lifters and pushrods while at it and also have a look at the rockers for excessive wear. a valve job can be had for about $50 to $100 depending on what's involved so i'd say do that too unless you're planning to rebuild the whole thing soon in which case you might want to wait.

[Torch_Ind]

you probably should, i would replace the valve seals, lifters and pushrods while at it and also have a look at the rockers for excessive wear. a valve job can be had for about $50 to $100 depending on what's involved so i'd say do that too unless you're planning to rebuild the whole thing soon in which case you might want to wait.

  also check for vale guide wear or scoring could have had valves stick

[JimmyFW1]

also just wondering  if you only replaced #3 cylinders valves the first time and didn't take any attention to the rest of the valves. cause your state it was #3 last run and #2 this run. 

to me it could be wear and tear and you only fixed what broke last time not rebuilt the rest.

Yes, only #3 was fixed last time because I was on a road trip & didn't do the work.
I have pulled the head myself this time, and see the damage to the #2.

I have since found a fellow Jeeper here in SC that has cheated on our beloved 4-banger by doing the 350 V-8 conversion (although it was a job well done).  He has given me all the parts he rebuilt, including a freshly reman'd loaded head.
Plus a few little extras...

[sharpxmen]

Yes, only #3 was fixed last time because I was on a road trip & didn't do the work.
I have pulled the head myself this time, and see the damage to the #2.

I have since found a fellow Jeeper here in SC that has cheated on our beloved 4-banger by doing the 350 V-8 conversion (although it was a job well done).  He has given me all the parts he rebuilt, including a freshly reman'd loaded head.
Plus a few little extras...

so are you going to keep your lower half? (i mean block, crank, cam, etc) - if so you should still figure out what happened with your valve (check my first reply to you for a list of causes).