jarhead0415

So can I just replace the rod bearings and call it good?

The entire oil system is going to have to be cleaned out somehow too, ive got metal shavings all over the place. Don't know how to go about that either.

Any advice is much appreciated. If I have to go through the whole bottom end of the motor and replace everything, then thats what I gotta do. But if not, I dont want to.

Radi

As long as the crank is still in good shape, sure. Might not hurt to get some plastigage and check the clearances, esp. on the bad piston for peace of mind.

I flush them with a couple gallons of cheap motor oil, start, drain refill 3-4X.

jarhead0415

the crank looks alright, but I wouldnt be surprised if it isnt. I'm trying to decide now if i should take it out and get it balanced/machined. It happened waaaay out in the sticks. By myself, no cell phone reception, middle of the night. I very very very veryyyy slowly nursed it back to my house (Lots of stopping and turning off the motor, took me 6 hours to drive what normally takes an hour.) so I probably screwed up the crank, knowing my luck.

I quit working on it for the night, and im going to finish pulling it all out tomorrow.

I've heard that if you replace one bearing, all of them have to be replaced. Is that true?

I've rebuilt a chevy v8 once with a friend, but never a 4.0. So I'm a little hesistant to dive into it right away.

Radi

You don't necessarily have to replace all the bearings, but it's good practice. Since you are seeing flakes in the oil I'd highly recommend it. Crud gets embedded in the soft bearing material and comes back to bite you later .

The 4.0 is a sweetheart to rebuild. Think tractor motor, lol. If you can handle a GM V8 you can do this easy.

Gorillaxj

Sorry to say but the crank is most likely trashed... But in the off chance its not you can just replace the one bearing.. but they are all going to be worn, and if your in there.. why not do them all. they aren't that expensive. I would also check your cam bearings or replace them for the sake of it while its out. Personally if the motor is out and it has more then 70K on it I would rebuild it. no need to do it twice for something else going bad. But that's just how I work lol, I have seen people fix just whats wrong and slap it back together...

jarhead0415

Yeah, I definitely don't just want to band-aid it so I'm probably gonna rebuild the whole bottom end, just wanted to get some perspective before I started.

I'm starting to think maybe ill just stroke it while I'm at it. I mean why not ya know? haha. RPM Machine has a pretty inexpensive 4.5 kit. Y'all heard any good things about it?

jarhead0415

hahaha "think tractor motor". i love it. its a 94 too, so there isnt as much crap as the newer 4.0's.

DFlintstone

Twice recently guys have stuck a set of rod inserts in after having one go. One really didn't look so promising. Both seemed to go OK...for the moment. Since (just the set) is only about $20 at rockauto, it might be worth a shot if you don't mind gambling what, $100 and a weekend. (oil, gaskets, band-aids!) I had it work once, and not work once, not in Jeeps though.

With one new pair you could plastigauge that one bad one and see if its really lunched, or out of round. (the crank journal).

Sorry Btw. Been there...doing 18 MPH in the dark forever, listening.....Bang bang. There was a bluish light in the distance. Closer....Closer...It was a 3 foot tall pyramid of pints of STP in a window under a fluorescent light, before the big climb over the pass to San Louis Obisbo! Added about two quarts and made it.

jarhead0415

Yeah, I'm going to take the rest of it apart in the morning and find out if the crank is out of round. Probably is. I saw new ones for like $180, if this one can't be machined back.

Tomorrow is my 21st birthday too, what better way to spend it than working on a Jeep right? haha

Yeah I was lucky that it was all mostly down hill from where I was to my house. Near Flagstaff, AZ to Prescott, AZ. Its like a 2 or 3000 ft drop in sea level. (flying up it at 75mph with 373's and 35's, is when it blew out on me haha) There were a few times that I could put it in neutral, shut off the motor, and just coast but they were few and far inbetween.

DFlintstone

Lucky you! After midnight, girlfirend, dog AND the cat. 56 Chevy step van w/dulies & 10.000 lb GWR, with the "pass" AHEAD. 2000 ft?. At San Louis Obisbow I put in a set of inserts in a sand parking lot in the wind. Made it 500 miles home. Whew...

Best luck to you. Idk where there might be specks to check the oil pump for wear.

I wonder if when they were ruining good engines in "cash for clunkers" , if they ruined the crankshafts also....

jarhead0415

I've seen a couple rebuild "kits" with oil pumps, so I'll probably just replace it.

Should I get a rebuild kit, or should I just order everything individually on Summit Racing, or Quadratec?

I have a funny feeling about the word "kit", when it comes to this.

jarhead0415

Have y'all ever heard of this company or do you think they are worth it? $1156 for a reman. I need to get my Jeep back on the road in the next 2 weeks. My dad needs his truck back, so I'm just gonna get a new one and stroke the old throughout the course of this year.

Here's the link to the site.
http://www.rebuilt-jeep-engines.com

DFlintstone

Sorry, no help here. I guess I've been lucky, I seem to always find what I need locally. I guess for a long block, with the head and all that doesn't look bad if they don't eat you up with tax, shipping and core "business".

You gonna check your crank?

ixta70

I had the same problem with my jeep but I had low oil pressure and it caused a misfire in the 6th cylinder. My rod was missing too, fell straight down.

What you should do is replace all and check to make sure that the lifters aren't bad too. One of mine was bad too, but I ended up replacing the whole engine. Take the lifters out through where the Rods are with a magnet. They come right out, if I remember correctly.

TheJerm

How about just finding a good used motor locally? They usually range from 300-900 depending on area and mileage on the motor