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Old 02-15-2010, 11:39 PM   #1
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Default 4.0 Head removal

So I 91 XJ that I ran engine cleaner through and caused a bigger problem. So now I have a valve issue (cylinder#2 is non functioning) When I pulled the valve cover and rotated the engine I found one of the valves wasn't operating, I believed it to be the exhaust valve since it was backfiring up the intake manifold.

FIRST
I know the head has to come off on the 4.0 to mess with the lifters. How hard is it to remove the head, is it as straight forward as it looks or am I gonna get a nasty surprise? I've done plenty of headgaskets on chrysler 2.5l 4cylinder turbos and that's a fun little adventure the first couple times.

SECOND
How much damage is being done to the piston rings since it's still compressing but has improper airflow so it makes more drag and no power. I know this because I tested it today w/o a spark plug in the place and it runs likes it's supposed to.

I don't have a whole lot to drop in this repair (about $500) What am I up against?
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Old 02-15-2010, 11:47 PM   #2
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not to bad to do. i unbolted the intake and left it to the side and then just unbolt and remove.how long has it run with out the exhaust on #2. you may want to remove the lifter and inspect the cam is you can get a gauge on it
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Old 02-16-2010, 03:33 AM   #3
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Late-gen MDS setups close the valves on deactivated cylinders to "turn them off", so you probably don't have any ring trouble.

I find it easier to pull the head and manifolds as a piece, but I'm a big guy and have an engine crane handy as well. The manifold gasket, if it needs to be serviced, is done on the bench.

Check the cylinder head screws before you start work - if they're not painted, get some bright colour of paint (I typically use yellow or red.) If they're painted, order a new set. The 242ci head screws (per FSM) may only be fully torqued twice - they're a modification of the old Torque-To-Yield (TTY) head screws used on Diesels. Yes, they can and do fail (rupture) if you try to torque them a third time - I've made a decent amount of money burning them out of blocks sitting in place...

Replace the exhaust & manifold hardware with bronze (best - check marine supply houses) or SAE5 carbon steel. Don't bother with CRES - it's not enough to help - and SAE8 loses strength faster than SAE5 due to heat cycles - it won't be long before the SAE8 is actually weaker than SAE5!

Undercar, like on the clamps and flange hardware, use marine brass. It won't corrode or seize, so it will be easier to remove next time!

Make a "thread chaser" out of a hardware store-bought SAE8 1/2"-13 x 3" screw by cutting two or three longwise flutes down the side. Run it down the hole and back out to clean the crappola out - clean off the screw and repeat through all fourteen holes.

NB: The #11 cylinder head screw hole (driver's side front) extends into the coolant jacket - be sure to coat the threads on this screw with something like LocTite PST, plumber's PTFE pipe dope, or RTV. Treat This Point As Important. (I've used the first two with good results. There's no reason the third shouldn't work - I just haven't used it yet.)

Manifold hardware gets LocTite #272 (or equivalent) or don't bother. It's not tight enough to require never-seez, and other grades of chemical threadlocker will break down due to heat. Replacement studs may be made using 3/8"-16 brass threaded rod (cut to 2-1/4" long,) and replacement screws should be 3/8"-16x1-1/4". Retain the dish-shaped washers and reuse them. If you can't get 1-1/4" long screws, get 1-1/2" long and a bag of flat washers - take up the slack by using flat washers between the screw head and the bowl washer.

Torque specs for just about everything should be on my site in the Tech Archives - taken from FSM. If I don't have your year (yet...) pick a year close to yours.
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Old 02-17-2010, 01:43 AM   #4
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Quote:
Originally Posted by djritter1122 View Post
not to bad to do. i unbolted the intake and left it to the side and then just unbolt and remove.how long has it run with out the exhaust on #2. you may want to remove the lifter and inspect the cam is you can get a gauge on it
It's been running this way for about a month and a half.

Excellent info 5-90, I will keep all this in mind when I do it. Hopefully it will hold up until May or June.
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Old 02-17-2010, 06:10 PM   #5
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Quote:
Originally Posted by 2.5TURBO View Post
It's been running this way for about a month and a half.

Excellent info 5-90, I will keep all this in mind when I do it. Hopefully it will hold up until May or June.
I'm not sure I'd put it off that long - maybe a month at the outside. It probably isn't a problem now, but it probably will be a problem later...
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Old 02-17-2010, 09:59 PM   #6
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Its been my experince that even with new lifters the cam can still fail, to help slow this down coat the new lifters with ZDDP Paste. Just my .02
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