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Codybelec

Pulling my 4.0L what should be done?

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I bought my MJ with a blown 4.0 so I’m swapping one in from an xj. I have limited money but I wanted to change all the seals and different things I should while I have the motor pulled thanks.

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If you have it out, change oil pan, rear main, valve cover, distributor, etc gaskets. Install new oil pump. Install new timing chain and gears. All pretty simple and straight forward when engine is on a stand. 

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That all really depends on how much money and time you want to put into it.  How many miles on the new engine and have you seen/heard it run? 

 

At a bare minimum I'd say do the oil pan, pump, rear main, and all the freeze plugs since those are difficult to do while in the truck.  You could do the timing chain and gears but I've never heard those as being an issue unless the motor is at like 400k miles. 

 

If you have the money and time, change out the exhaust manifold because the factory ones crack and do the valve cover gasket.  

 

Side note, where are you located?  I'd take that blown motor off your hands if you were close. 

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I live in Nova Scotia I have 2 blown 4.0l here.. I havnt heard the motor run and I def don’t have much money lol 

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I would make sure the 'new' turns over by hand and you can't hear any rattling or anything in the motor. I would do minimum what the others said, but if you could, do a re-ring kit. Dingleberry hone the cylinders and slap it back together.

 

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11 hours ago, Codybelec said:

I live in Nova Scotia I have 2 blown 4.0l here.. I havnt heard the motor run and I def don’t have much money lol 

Dang, wrong country. 

 

Turn it over by hand to make sure it's not bound up, then I would prolly pull the head off as well as the oil pan and inspect everything in the bottom end before reassembling.  You can find out a lot about an engine by investigating the head gasket and cylinders. 

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Personally I would check compression before pulling the head. If compression is close to equal on all cylinders then I would leave the head and head gasket alone. The only things that I would do with the engine out of the truck is the rear main seal, oil pan gasket, and intake/exhaust gasket. Everything else can be done without too much issue with the engine in the truck. Have you looked at the oil? Color/ consistency/ taste etc. Between that and a compression check you should be able to make a good decision. Value my advice for exactly what you paid for it though. Good luck.

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sounds good I'm going to replace the RMS, oil pan gasket, exhaust manifold and frost plugs before i out it back in

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I suggest the one-piece rubber pan gasket :L:  and be very careful with the RMS.  brass punches only!  also a double lip RMS exists if you find that there is deep scaring in the crankshaft where the single rides.

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If I remember correctly, with the pan off you can check how much slack is in the timing chain.  Mine was pretty loose well before 200K.  I replaced it along with the harmonic balancer.  Easier to do while engine is out.

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I will say that for my engine swap I looked at the timing chain when the oil pan was off and noticed a lot of slop. Didn't have time, money, or parts to fix it then. 15,000 miles later and everything still seems good *knock on wood*. It is on my 'one day' project list. So IMHO the timing chain can wait if you are really in a time and money crunch.

 

The one piece oil pan gasket is definitely the way to go btw. Make sure to use the install clips as it makes it way easier for holding it in place and getting the alignment right. I didn't find them at the bottom of the box till I was already done struggling with it :brickwall:.

 

Good luck.

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Not much money = I wouldn't do any of it.  Unless something is obviously wrong, and at that point I'd probably reevaluate using that engine.

 

Where are you getting this engine?  It's pretty easy to exceed the value of a good used engine by throwing parts at it.  Last 4.0 I built up was a free longblock, it was a waste of time/money, I could have found him a tight complete engine for far less than he was into it for when we were done.  His build, not mine.

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