6lugger92

Took an offroad trip out to durhamtown Ga and got a little to gnarly in a mud hole. Ended up hydrolocking my motor (a 1992 3vze with 275K) and after blowing out the cylinders i got a real good knock going on. So I pulled the motor to investigate and when checking the bearings i didnt see anything abnormal. They all looked silver and similar. No bronzing no mishaping. I only ran the motor for probably 20 minutes tops all together after the accident so is it possible to get rod knock without visible damage to the bearings? what else could be causeing this issue? and last question, this is my first time looking at rod bearings so what are some less subtle signals of a bad bearing?

millball

Bent rod/rods, cracked piston/pistons??

Rod bearings would be the last place I'd look.

bswarm

Check the wrist pins. If the heads are still on but the oil pan & rod caps are off, grab the rod and push/pull/twist to see if there's any freeplay. Plastigage the bearings too.

6lugger92

Ok ill try to wiggle the rods and ill plastigauge the bearings, millball why would bearings be the last place you look? also would hydrolocking cause a valve seat to drop, i know that causes a good knock

millball

When you hydrolock, the unstoppable force meets the imovable object, that is, water cannot be compressed, and somethings got to give, right GD now!!
Usually the weakest thing.
Most often will be the con rod and/or piston.

Crankpins and rod bearings are very, very, durable and not likely to give way
in the immediate aftermath of hydrolock........unless you broke the crank.....

6lugger92

I always thought that the knock comes from the bearing allowing play, if that isn't occurring could the pistion or rod being bent cause a noise? A bent rod in my eyes would make the bearing go bad. Also assuming a rod/piston/bearing is fudged what's the most cost affective, correct way to replace it to get my motor reliable again?

bswarm

I've seen broken wristpins, then again I've also seen rods sticking out of the side of a block with a mostly intact wristpin, and what was left of the piston was still in the top of the cylinder.

Budman1

Please pass the popcorn

Bud,😉

6lugger92

The motor got hydrolocked, then knocked. So something is definitely fudged somewhere. But considering non of the bearings where badly harmed, the cranks fine, leaving me with positions and rods. Or something in the top end. Is there a way to do Pistons from the bottom end or does the head have to come off?

scope103

I'm with bswarm. My best guess is a bent connecting rod. I'll bet if you look very carefully you'll see where it is hitting the side of the crankcase. It doesn't take much. You might not even be able to see the bend until you lay the connecting rod out on a clean table next to a good rod.

Shady Cadence

Did you bother to figure out which cylinder was doing it?

A bent rod could cause a knock, but I'd say you broke a piston. Given that the engine ingested water while running, a complete replacement would be your shortest route to a reliable vehicle again.

Unless you want to rebuild this one. But I mean really rebuild it, not just get a parts kit and slap it together. These aren't legos. Each bore should be measured at least six times for diameter, on yours I'd do no less than a dozen within the top two inches of the bore.

Remember, at least one part broke. Now which ones got stressed too far, but didn't fail?

millball

Pistons and con rods can only be serviced out the top.

Nothing short of complete dissassembly will even get you started.


Then,, Let the measurements Begin!!!

6lugger92

When I checked the bearings I looked for signs of which cylinder was doing it and could find any clues, then again I've never been into the bottom of an engine before so with this new info I'll go back and look for more signs. Also the crank bolt was extremely loose, turning the crank to cycle the Pistons was enough to break it loose. Not sure if that says anything. I'll have more info tmw when I go back into it. Seems like a new (to me) 3vze is needed tho. I'm having a hard time finding one in running condition

millball

It seems you are fixated on loose or worn con rod bearings being at the root of your knock.

They are most probably not.

Look to the pistons and con rods.

6lugger92

Found the issue! Got a light in there and the second I looked at the first cylinder from the front I noticed a super bent rod, so bent that the bottom of the piston was slapping the top of the crank and made about two 1/8 inch gouges in the bottom of the piston, crank doesn't seem to have any damage tho so I guess the crank steel is a lot harder then the piston. What's the procedure for fixing this cheaply? ("Cheaply")

millball

Can't be fixed cheaply.

Might be fixed by complete engine overhaul that would include new pistons and con rods.

Least money might be a used running engine, if you can find one, but you never know what you're gonna get.

Education is always expensive.

6lugger92

Looked again and the 1st and 6th are bent and gouged

scope103

You'll have to replace at least two pistons and connecting rods, and you'll probably want to measure the rest.

The problem you now face is working on 23-year old engine that has gone through some major trauma. Maybe two pistons and rods is all you need. But probably not, just from the age factor alone. So you may get in part way, and discover that it's a lot more money before you reach the end.

I'd certainly shop for a replacement engine; you're buying an "unknown," but that's compared to your all-too-well known current engine.

6lugger92

Yeah used motor will be going in soon, I'll keep this one on the stand to tinker with and better understand how it all works. This is my first time taking a motor out so it'll be cool to have to mess around with and "rebuild" slowly

6lugger92

When I do rebuild what should I go to the machine shop for, boring and decking? How much would that whole machining shizbang usually run?