Hi guys, might be swapping out my 4.0 soon as im having some engine trouble lately . Was hoping to get a while out of the truck before i had to do anything major, got a few months and that was about it. Chain rattle started on cold starts and now its starting to show while in mid RPMs. I have changed out the chain tensioners to no avail.

1 )
Will basically any motor work from the 4.0 SOHC's? My truck is 03. Also do I need any of the computers or chips or anything like that or just the motor?

2) Is it cheaper to have timing chains redone or just to purchase a used motor with less mileage.

3) Is it a huge job to remove the motor? I have the time, space, and most of the tools ( may need to buy a shop crane or cherrypicker ) I am debating on going at it myself. I've removed trannys and stuff from jeeps however never took out a motor. I'd imagine its just a series of small steps.

Thanks.

 

If you swap engines, you still have to:
Drain the fluids
Disconnect all the wiring
pull out an engine
put an engine back in
hook back up the wiring
refill fluids

so none of that should be included in the decision.

If timing chains need to be changed then get the cost of those parts

If you want a rebuilt engine then get the cost of that, not a used engine, you already have a used engine, lol.

Compare those costs and benefit for each

Outside of the timing chain issue, which goes away when new design parts are installed, the 4.0l SOHC engine was very reliable and will last over 400k miles

You rent engine hoists, 1 or 2 days to pull engine out, 1 or 2 days to put it back in

You buy engine stands, craigslist, $40-$60 then sell it when you are done with it, just like the guy you will buy it from.

Also when looking on crailslist, there are often mechanics that moonlight, they have hourly rate and will come to your place to assist or get you past any hard parts
So no matter what you decide I would do it yourself, and hire help if needed


You need to support front of transmission with engine out, or drop transmission, only a few more wires and bolts

Engine hoists have limited lift, so you have to plan for that
As you lift up the engine it's weight is coming off of the front suspension, so body and rad support also lift up, so truck could lift up too high and engine can't be pulled out over rad support.
On some front suspension you can chain it, so when you lift the engine the body/suspension reaches chain limit and is held at that level.
On others you remove the front tires and lower the front down so when it lifts up you still have the clearance, not too low, engine hoist needs to slide under front end

Regardless of the choice I would also drop off truck to muffler shop and tell them you will be pulling the engine and you want them to loosen all exhaust manifold bolts and header pipe bolts, replace any that break and then "snug" them back up.
Should run about $60-$80, ask first
You can spend 1 to 6 hours on ONE stuck, stripped or broken exhaust bolt
These guys do this every day, they have the knowledge and tools to deal with it, and replacement parts on hand.


You can use a 1997 to 2012 4.0l SOHC engine, 4x4 engine will have extra balancer shaft inside but doesn't matter, they can be mix and match.

You will need to use your 2003 upper and lower intake so vacuum lines and wiring match up

Take LOTS and LOTS of pictures, use lots of white tape and sharpie for labels

Thermostat housings leaked on these engines, so consider replacing it
Also always install new rear main crankshaft seal, they are cheap and hard to get to so why not

 

I appreciate it highly, i admire how much knowledge you have on these subjects. I have the time to be at it so i'd rather do it right. You've made a valid point, i currently have a used engine ( second one ) and still needing another one so I may as well try to rebuild it. To have a good rebuilt engine outside of timing chains and gaskets, is there anything else major that should be done? I am a bit green when it comes to motor work. Other then that I will run with what you've mentioned and come back from time to time with questions I am sure. Thanks, !

 

You will be fine, just wrench work really

You could do a compression test on all cylinders, remove all spark plugs for the test

4.0l SOHC engine runs 9.7:1 compression ratio
I use 18 as multiplier, 15 for air pressure at sea level(14.7), and 3 for mechanical rotation of starter motor
18 x 9.7 = 174.6 psi would be expected at sea level

But point of compression test is to get an average and then see if any cylinder is 10% away from that average indication a possible problem
Getting highest number is NOT the point

If you get 160 to 170 readings that is fine, compression gauges are rarely calibrated cranking speed can be low, you could be at 1,500ft above sea level.

If average is 165psi and you have 1 cylinder at 140 then you will want to retest that 1 cylinder after adding a teaspoon of oil via spark plug hole, dip a straw into a bottle of oil, put finger over the end then lift it out and out it in spark plug hole.
Install compression gauge and retest
It will go up
If it goes up close to average, 165, then rings are bad
If it only goes up by 5-10 then valves are bad

If all cylinders are within 10% then just doing the timing chains should be all you need to do