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What to look at while engine is apart?

J

J1MB0B

NAXJA Forum User
Location
Tacoma
I have at least one broken piston skirt. I haven't checked any of the rod or crank bearings yet.
My plan is to replace any damaged pistons, re-ring all of the pistons that don't get replaced, new bearings on all the rods and crank mains, and replace the lifters. Also going to do the rear main seal. If I can get away with it, I would like to do all of this without pulling the engine.
Is there anything else I should look at while I've got everything apart? Anything on the transmission to look at?
I just did a head gasket and went through the head a few months ago, so I know thats good.
If any of the lifters are badly worn, will it hurt the cam to put a new on in? How about the push rods?
Are there any specific brands as far as pistons, rings, and bearings, to stay away from?
 
In framing is a lot harder. The extra work to pull the motor makes building one so much easier. Keep that in mind. Putting new lifters on is fine, bit if you reuse any they must go back where they came from. I'd do a new timing chain while you're there. Clevite and sealed power are fine, cloyes is good for timing chain parts. You can do a frt pump seal on trans if it worries you.
 
How many miles on the engine?
 
1) Cleanliness is paramount.

2) Pull the engine. Much easier and besides, the crank can't be pulled in frame. Putting new bearings on a crank without at least polishing it is, IMPO a waste of time and money.

3) You can put new lifters on a old cam, but never old lifters on a new cam.
 
There are about 225k miles on the engine. Other than the ticking noise that turned into a loud clanging noise, it runs great. Still has lots of power, oil pressure is good, no smoke in the exhaust, no sludge in the head or oil pan. I know its a piston skirt because I pulled pieces of it out of the oil pan. Im thinking rod bearings because I can feel the movement when I wiggle the rods on the crank with the caps still torqued on.
I think Im going to work on pulling the engine for now.
 
Well that "wiggle" is clearance. There's a whole bunch of clearances inside of an engine. The engine must be disassembled, measured and checked versus specifications. 225k is probably enough to assume the cylinders are out of round and tapered, and a broken skirt means it's more than likley scores up as well.

You have two options,

rebuild it, the right way -or- buy a long block.
 
^^^^^^^^^^^^^^^^^^^
WHAT HE SAID!!!

I am still wondering if there was any year range of 4.0L engines that had piston skirt problems.
 
The piston skirts in the 4.0 are long, and the factory compression distance is short comparatively. This is not a "problem" as the motor is designed to make its power from idle up. Should a 4.0 be spun to 5300 where it shuts down the fuel pump? No. No reason for it. Should they have shut the pump down sooner? I don't know, that's up for argument. I can tell you though, that the amount out of round at the skirt in a 4.0 is a bit more than normal, but it makes sense for what they asked the engine to do.

My opinion? The compression distance to piston height ratio from the factory is a little tall for the material it's made of. But hey, they don't break skirts very often, and they require almost no internal engine work to 300k (usually) what the hell more could you ask for.
 
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I found pieces of the #2 piston in my oil pan. So far, I haven't seen any scoring on the cylinder walls.
Ill look better tomorrow. I'm also going to pull all the bearing caps and check for damage. If everything looks good, Ill probably just stick with the original plan and change the broken piston, new rings all around, and roll in some new bearings.
I would love to pull the motor and rebuild it, but I'm on a pretty tight budget and its my daily driver, so I really need it back on the road. I'm going to pick up a long block with a blown head gasket and work on rebuilding that over time to spread out the cost. Hopefully mine will holdout until the spare is finished.
 
XJ-ARNIE said:
So what did you conclude caused the #2 pistion to grenade?
Click to expand...
I have no idea. What ever it was, it took 225k miles and 16 years to do its thing. I know this is just a bandaid fix and but it will only cost me about $250 and some time. Its my only vehicle, so I need it back on the road ASAP. Im pretty confident that it will get me through until I get the spare motor rebuilt.
 
If you need another 50k miles or so, I would do the shade tree mechanics overhaul. That means replacing the main and rod bearings with OEM size, as long as the crank has never been turned. You can tell how bad things are first by using Plastigage to check clearances.

Pull the pistons and hone the cylinders and cut down the piston land ring, put in fresh pistons and rings. Do not go with chrome rings, go with standard. The chrome rings are too hard to seat again if you didn't bore and crosshatch.

While you are at it clean the valves and lap them. Replace the valve seals.

Yes the engine will be a bit loose, but it will work.
 
Hypoid said:
^^^^^^^^^^^^^^^^^^^
WHAT HE SAID!!!

I am still wondering if there was any year range of 4.0L engines that had piston skirt problems.
Click to expand...


Yes. The newer the 4.0L, the more likely it is to have piston skirt problems. It seems that the bores are all different and each piston was fit to the bore as the engine was made.

My personal. $.02 - since we are dealing with Chrsyler, quality was never job 1 .. or 2 ... or anywhere on the radar. A lot of engines probably never got the right size piston and that is why many 4.0L engines piston slapped from the factory. Which is often inappropriately referred to as "lifter tick".

Very rarely has a Renix or an early HO 4.0 broken a piston.

My 2000 has a very bad case of piston slap. I'm hoping it waits to scatter a piston until *after* I have a place with a garage. At which point, I will find an early HO 4.0 or Renix 4.0, freshen it up and put it in.
 
Having just rebuilt my entire engine for the 2nd time.
A few tips I have for you.
#1. Its been said. but Meticulously CLEAN is the only way.

#2. buy yourself some an-aerobic sealant. The first time I built the motor. Leaks galore.
This time. I sealed everything with that stuff and 0 leaks so far.

#3. post pics here if you have any questions. the jeep motor is.. well... interesting.

One thing I gotta add. These 4.0's are near invincible. bar the timing chains. if bearings look good. she may have tons of life left.
If you got the motor out... it you only need the cylinders touched up. might be worth throwing some money into.
Also. If your pistons are dirty as mine were. go to your local auto store and get some berrymans parts dip. dunk your pistons. they will come up brand new after 2 days sitting in that stuff. takes like 6 days to do all the pistons. 2 at a time. 2 days each. at the end of day one. you gotta pull and just lightly remove the carbon to get to the next layer.
 
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Picked up a JY 95 4.0 motor to rebuild over time as a replacement for our high mileage motor.
Looking at Engine seal kits it broken up by different years, does it matter which years kit I go for?
I'd like to grab a later 4.0 kit with the better seals.

When I get around to tearing this motor down anything in particular I should look out for?
It supposed to have 118k.
 
Change number 5,560,231:
I got it all apart. Number 2 piston is about half gone. No scoring on the cylinder though.
The lifters are worn pretty bad, and the cam looks like poo poo.
I think Im just going to pull the trigger on a full rebuild. I found a shop that will bore and hone the cylinders, rebuild the connecting rods, grind the crank, line hone the crank mains, clean the block and install cam bearings and freeze plugs for $440. Sounds good to me.
I will be doing some towing. A 4x8 trailer with some camping gear and a couple of dual sports at most. Should I stick with a bone stock build or look at small upgrades?
Also, can anyone recommend a good book that will cover the rebuild process in detail?

I really do appreciate all the help so far, this is by far the best jeep forum I have found yet.
 
Aside from stroking it. you can upgrade the timing chain to double roller. water pump. and oil pump to high volume.
melling makes the oil pump.
flowkooler makes the water pump.
and I got my timing chain from russ from the jeepstroker forum. Couldn't find it anywhere else. but I got the roll-master. its really nice.
Its not a huge price difference. between stock and the better stuff.
 
My stroker ate up the stock-style federal mogul timing set after a couple years(no it wasn't the CKP sensor crank, no-start fault--THE DIZZY ISN'T SPINNING!). I bought the nice Rollmaster set too.
 
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