Bad Rod Bearing

[mliebal]

Hey all,
I have a 4x4 96 4runner with 3.4 and 300k miles.
Not a daily driver anymore, but great for pulling dirtbikes, jetskis and of course driving at OBX surfishing.
I recently changed my oil from my std M1 5w-30 to 10w-40 Syntex high milage oil. So driving 30 minutes into a 4 hour drive pulling 3 dirtbikes and gear, we hear ticking. At engine speed.
After testing everything from compression to leak down to setting valve shimms (only 2 out, though barely) still had noise. No flex plate issue.
Used stethoscope (sp?) located to cylinder 3/5 (right bank towards rear).
Took vehicle to trusty Toy Master mech. He says worn connecting rod bearing on crank. He says since I did not want to spend big $'s now, I might could drop diff, open pan and if crank surface not too gouged (ie bearing not spun) put in smaller sized bearing on connecting rod.
Ever hear of this?
Vehicle is on blocks, with diff ready to be dropped.
Interested if anyone else had worn connecting rods or experience in this area. Am I wasting time effort doing this, should I just wait 6 months until I can fix right?
Thanks

 

[98OzarksRunner]

If the crank is scarred you'll need to have it turned and put in smaller bearings (pull motor, tear down, etc.). If it isn't scarred, put in STANDARD rod bearings. Undersized bearings are for turned cranks and generally come in .010, .020, .030, and .040 undersized for the 3.4 motor. (You might find some .002 or .005 undersized bearings but not likely. Clevite only makes them in std, .010 and .020) If it's not scarred, it generally won't be worn enough to be out of spec.

The best way to check it is to pull the rods away and measure the rod journals with a micrometer. The Toyota spec for the 'crank pins' (apparently that's Japanese for rod journals) is 2.1648" to 2.1654". If it's less than 2.1648" you'll need to have the crank turned or it will have too much clearance.

Usually if it's knocking it's worn enough to scar the crank. It's worth checking though.

 

[mliebal]

Thanks Ozark!
Toyota does make a range of standard rod bearings that are not truely undersized. If i'm lucky on the crank finsh and that the bearing in there is not already the smallest (standard) size, then I might get some miles before a real engine replacement or rebuild. I'll try to take some pics of the crank once I get the rod removed.

 

[mliebal]

Well dag-nab-it! Pulled the front dif (fun!) then dropped the oil pan.
The under side looks lightly tan but very clean.
Everything felt tight.
I pulled the caps off of connecting rod for cylinders 1,3 and 5. Wow! the parts look almost new!
No visible wear marks, just some polishing. The crank pins look perfect. Not a mark or any sign of wear. This engine has 300k miles on it. That calculates to roughly 750 million crank rotations! Wholly cow batman. These parts look great.
I will mic the crank pins and replace the bearing, but I dont think this is the cause of the engine noise.
I guess I will pull the spark plugs and turn the engine over by hand (or maybe by starter) and see if I can detect where the noise is coming from?
Any ideas?
I am officially baffled!

 

[98OzarksRunner]

It's not this sound is it?

http://www.toyota-4runner.org/3rd-gen-t4rs/138032-rattling-sound-only-when-accelerating.html

If so, we can eliminate rod bearings.:happy:

 

[mliebal]

Nope mine is all the time except when letting off gas. Loud ticking almost knocking sound. Engine has never been overheated. I'm thinking scuffed pistons.

 

[mliebal]

Still have ticking noise.
I put the new connecting rod journals in. No difference.
I felt each rod carefully to see if there was any vertical play in the rods.
All felt tight, no play felt whatso ever.
I went back with the stethoscope, I could hear plenty of noise from the fith cylinder injector. When I unplugged it, the noise went 100% away. Hmmm!
I tried unplugging that spark plug. The engine slowed but the noise was still there.
I just finished this morning puttting a reman'd injector in. No real improvement. And the noise still goes away with that injector unplugged. The noise still stays with that spark plug pulled. The noise stays when I pull other injector plugs.
Im guessing:
1. Still a bad injector
2. A knocking piston, though why no noise w injector pulled but noise w plug wire pulled?

Other thoughts?
I have previously pulled all belts, check valve clearances, inspected flex plate.

 

[Singtoe]

Sounds like detonation.

Pulled fuel injector wire and no fuel - no pinging.

Pulled spark plug wire, still has fuel, spark knocking from detonation.


Try seafoaming it. Flood the intake PVC port with Seafoam and let it stall out. Let it sit overnight to loosen any carbon in the combustion chamber. Start it up the next day and smoke out the neighborhood.

See what happens. The worse is that you waste $7 on a bottle of seafoam.

 

[jsukey]

Seems almost easier to just find a lower mileage replacement engine out of a wrecked truck and drop it in. I just ran across a low mileage (130k) 3.4 last night for $1000. It even came with a 60 day warranty.

 

[mliebal]

Well, I am opting for a replacement engine.
But I could not do that with out knowing what the issue was.
I tore the whole dop end down (big job getting the heads off!).
The number 5 piston was badly scuffed. The top ring was stuck and has aluminum smeared to keep the ring stuck. Not sure what happened first. Metal scuffing then stuck ring or vics versa. Bore actually looks good. One mark that is barely finger nail catching.
Wrist pin was super tight.
So final thought is that the clicking, happening except at decal, of with injector plug pulled was piston noise in cylinder.
Thoughts?