OK, so here's the story. Cracked a head at 140k or so when I overheated it, and during the head replacement I found that the head gasket had been leaking for awhile, finally made it's way between cylinders 3 and 4 (or is it 5? I'm always confused on how they number them in a V8!) Was there extra wear in these cylinders because of water leakage? Who knows.

Anyways, fast forward to late summer this year at 179k and I have a small "knock" happening when the engine is first started and you occasionally hear it when letting off the gas. I suspect a rod knock but decide to drive it until it goes boom. Well, it did, but the damned think kept running! Driving to work one morning and I pull away from a stop sign to a horrible noise, a loud "bang bang bang" and some smoke from the exhaust. I make a quick guess that the bottom end is letting go rapidly, so I turn around and nurse the truck home 5 miles as it knocks all the way there. Funny thing is it still ran smooth, just LOUD. Tried to keep the RPM's as low as possible, but the oil gauge still read OK.

Got it home and started the diagnosis. Checked the oil and found lots of shiny flakes, never a good sign. Draining it found LOTS of pieces of metal in it, so I figure that I'm totally done and it's time to retire my dear old Durango at last. I let it sit for a few weeks in the garage as I ponder on what to do, and drive around in a (gulp) Miata that my son and I have been rebuilding for my wife. (insert all of your masculinity jokes here please.... go ahead, get them out of the way!!! )

I finally get up the courage to pull the motor and take a look, figuring that I'm not out anything at this point. First, if you've never pulled a motor out of a 4wd Durango and are EVER contemplating it, let me recommend a few things. A big hammer, as many different 12, 13, 14, 15, and 16 mm wrenches, sockets, extensions, swivels, finger ratchets, flex wrenches, and whatever other tools you can find to get bolts out of places that you can't POSSIBLY get to. Stock up on Torx bits, I think T-30 is the one that I broke the most. Oh yeah, and your favorite drink, 'cause you're gonna need a LOT of it! Seriously, it was probably one of the hardest pulls I've evere done simply because you cant reach a lot of the bolts, and they are toght to break free with limited access. I dropped the front axle as it helped me with access to the starter, motor mounts, and just general room to work from the bottom. Not sure if it's neccesary, but it also gave me the opportunity to clean it up, check out the diff and CV joints, change the oil in it, etc.

After finally getting it out I tear it down and find that the number 3 rod bearing is gone. No, I mean GONE, as in missing. I find a few small chips here and there, but I can't find a bearing shell ANYWHERE. The rod itself is no longer round, but severely egg shaped, and Plastigauge isn't needed to measure the bearing clearance anymore, simply lifting it up and down with my fingers says it's 3/8" or so.

On to the timing chain area, there looks like ther may have been a couple of timing guides at one point, but now the tensionors are just hanging out there pressing on air, and there are bits of plastic and aluminum guides everywhere. The chains are still on, and the engine is still in time even though their is a WHOLE lot of chain slack slappin' going on. Time to pull the heads and I find....

Nothing. They're perfect. No marks, holes, metal, valve hits, smashed pistons. There wasnt even a ridge to catch my fingernail on at the top of the cylinder. I'm surprised, but now becoming cautiously optomistic that MAYBE this thing can be salvaged?

After 2 weeks of full teardown and cleaning up the parts, I find that the minimum parts that are needed are a crank (didn't even BOTHER measuring it for turning, # 3 journal was destroyed) a rod, all the bearings (they all had wear, metal fragment scrapes in them, etc.) and 1 piston that *I* ding'd when I tapped it out of the block upside down and it hit the shop floor. Fortunately it was the one attached to the #3 rod which was also toast!

Nothing ventured, nothing gained, I purchase a crank kit from Autozone for (get this) $270 INCVLUDING the $60 core charge which I got back. Gotta love internet shopping coupons! The rest of the parts came from Rockauto or Ebay but are legit and name brand parts, just cheaper sources. With nearly 180k on a 10+ year old truck that doesnt owe me a dime I can't justify spending $1k+ on parts or more on a rebuilt engine. If it comes back to bite me sometime then so be it, I'll call it a learning experience and my boys have had fun rebuilding their first engine.

Total $$$ outlayed was approx. $525 not including fluids, beer,and the therapy time needed for my boys after hearing me struggle with some really tough bolts.

I flushed the block and cleaned the oil passages, replaced the freeze plugs, bottle brush honed the cylinders, replaced the rings and replaced one piston / rod assembly, replaced the oil pump, all needed gaskets, and timng chain guides / tensionors. The chains and sprockets were reused as they were changed out 35k ago. Head and bedplate bolts were replaced (TTY bolts are used) however when I compared the originals to the replacements they measured up IDENTICAL. Jury is still out for me on that one. Only extra parts I had to buy were exhaust manifold repair flanges because I cut mine off, they were rotted up pretty bad.

Engine was installed last week (and I though REMOVING it was fun!) and turned the key on Monday. It simply started, ran rough and clicked for a few minutes, then smoothed out and sounded like an old friend again. Smooth with an occasional lifter "click".

Driving it for the first 75 miles was interesting. After it warmed up it would surge and stall when I stopped, and re-starting it would entail cranking it over for a few times and it would catch and run good. I figured the worst, that I had a vaccuum leak, or bad compression on a cylinder, low vaccuum, etc. so I did some searching here for advice and went after the battery, replacing it with a new one and changing out a rather corroded connector at the same time. I'm happy to say that the truck now fires up and idles perfectly at ~700, is dead smooth and quiet, and sounds great. I have ~200 miles on the rebuild right now with no leaks and no fluid useage. Will change the oil at ~500, then switch back to Mobil 1 at 1k provided everything looks good. Lifters have quieted down completely and oil on the dipstick looks perfectly golden and clean.

I figured I would give a few tips to others that ever have the need to go through this. I'm sorry that I didn't take any pictures during the process, but there really wasnt anything tricky about it other than finding some parts and freeing some fasteners. If anyone has questions feel free to post them, I'll do my best. I for one am VERY impressed with the 4.7 now that I've seen the thing completely naked. It is a VERY well built engine with a bottom end that should NEVER fail, assuming that it's cared for properly.

Tips:
* Mark / bag EVERY bolt you take out. The lengths are tricky to figure out when going back in. Trust me on this, I mixed a few of them up and they WERE bagged.

* DON'T mark the rods with a punch to identify them, it'll distort the castings. Use a tag, sharpie, etc. I used a sharpie on the side of the piston after I washed them off with laquer thinner.

* The pistons are cast with a "front" on them, and the caps are cast with a "V" on them indicating which way they go. PAY ATTENTION TO THEM!

* Make sure you take the crank key out of the core crank BEFORE you turn it in!

* If you fail to do the above, email me for the Mopar part # for it.

* Be VERY careful seperating the pan from the block. and make sure you get JUST the pan, not the windage tray as well. It's held in place by the oil pickup. Use a putty knife and seperate the pan from the gasket, remove the pan, then seperate the gasket from the block. FWIW I ended up re-using the windage tray on mine because my replacement was crushed in shipping and I wanted to get this finished. I simply cleaned up all of the surfaces well and put a layer of RTV sealant onto the block, put on the tray, the oil pickup, and then put another layer ov RTV onto the pan and bolted it in place. I have zero leaks. Reality is you probably *should* change the gasket though. i just couldn't get one right away.

*When removing the crank bed (kower half of the engine case) pry VERY CAREFULLY on the outside castings ONLY, ant tap at it with a mallet or brass bar. It's bolted, has sealant, is on pins, and is VERY heavy so it won't want to move easily. Oncve it does move you can pry it up from the outside, but DO NOT insert anything in between the machined surfaces that can mark them up.

* Likewise, when replacing the crank bed, MAKE SURE you use ANEROBIC SEALANT on the bedplate and put a thin line all the way around the oustside of it, staying at least an inch away from the bearing surfaces. I used Permatex Anerobic Sealant (which is made by Loctite) but research showed me that there is apparently a Mopar green sealant that should be used? Our local Mopar parts department didnt have it, and they told me they use the Permatex stuff as well. DO NOT JUST USE SILICONE OR ANY OLD GASKET MAKER!!!! It MUST compress extremely thin, and set up without air contact. Anything else also stands the chance of messing with the main bearing clearances. There apparently is some sort of spray primer that you are supposed to use with the Permatex stuff. I didn't use it (directions? We don't need to read no stinkin' directions!) and I'm happy to say that I have zero leaks.

* When assembling to check clearances, use the old original bolts and plastigauge to torque and make sure bearings are correct. On final reassembly use the new bolts and pay VERY close attention to the torque specs and patterns. I *believe* the Haynes manual is incorrect on the bed plate sequence and calls out to tighten some of the smaller bolts in twice at different times.I obtained and used the specs from Mopar directly.

* Clean off the surfaces for the thrust bearings (front and rear of center main bearing) EXTREMELY well and make sure new bearings are in correctly and facing the right way. Triple check your endplay, and if it's not right SOMETHING IS WRONG IN THIS AREA.

* Once you start assembling for the final time, put all your mains in place, the thrust washers, the upper halves / bed assembly, and the main (large) bolts finger tight. Take a screwdriver and pry the crank back and forth a few times. It'll help center the bearings correctly before they get clamped down.

*IMPORTANT ONE HERE: You *CAN* use "non-tang'd" bearings in a "tang'd" application. I researched and verified this in a few different places. However, if you have a "non-tang'd" rods you *MUST* use non-tanged bearings. It's the proper torque on the fastener / cap that keeps the bearing from rotating, NOT the tangs. MAke sure of what you have / need BEFORE you order the bearings.

*if you need to change your crank trigger wheel over to the new crank you may have to SLIGHTLY heat up the torx bolts holding it in place to get the loctite to break free. This was the hardest part of the job for me and I struggled with 2 of the four bolts. When putting it back on use loctite and verify that it's on correctly. It's not keyed, but the bolt pattern will only line up one way. It helps to have both cranks located side by side when doing this for reference.

*When re-installing the engine I STRONGLY recommend removing the radiator and front support so you can simply slide the motor in complete from the front. There is not enough room to do this from the top unless you remove the fan / water pump, and jockying around a 600lb + motor (guessing at the weight) to get it to line up with the tranny is tough enough. I used a couple of tapered wooden dowels that I made and tapped into the tranny side of the holes with the points facing forward to help guide the engine in place. Still, getting it to line up and slip over the locating dowels is difficult. Be patient.

I hope these hints help others that decide to undertake this rebuild. After doing this I wouldn't hesitate to do it again. As long as you take your time and triple check everything, this engine is actually pretty easy to work on.

Bob

 

Good write up

 

Thank you for the write up and all the great information. Sounds like you had quite the bonding experience with your boys!

 

Great post .

on the reinstall .do you have any tips .

i have a new motor in to the point that i have 5 bolts partially in but the drivers side is about two centimeters out and i can't suck it in the last bit with bolts . The drivers side Is almost touching but It won't budge on the drivers .

is there any way the splines aren't lining up ?being so close on the passenger side I can't see it being misaligned. Help!!

 

aaaaa

 

Hoenstly..too much to read. Sorry, I’ll pass.

 

Great write up and lots of information to read. I've done the timing chain and guide on these motor, they were easy as long as the front end was removed.

 

Thanks for the positive comments. 3500 mile follow up, all is still well, minor oil leak on oil pressure sensor, found that I must have cracked it on install. Engine used approx 1qt of oil from 1k to 3k. I suspect that there was more piston slop than I thought or the rings didn't seat perfectly. No real harm as oil is cheap enough as long as it doesn't get a lot worse.

PublicHair - no problem, not forcing you to read it. Sorry I'm so long winded. Hopefully you never have to rebuild one and need the hints.

Assuming that dakotarob got his done, but you should never use the bolts to draw it up like that, at least not much. If it's crooked or stuck there's something wrong. Wiggle it, lift or drop it, or change the angle a little. Jacking the tranny slightly sometimes helps as well. I struggled for a couple hours and walked away, went back to it and raised it slightly then it pushed right in. Patience......

Bob

 

That’s exactly why I didn’t read it! LOL

I doubt I’ll ever rebuild mine. I keep it pretty well maintained and only put about 2k miles a year on it. By the time I need something else, I can just sell it


Great write up tho for those who wish to go through such task..