ebelizard

Just as the thread title says, I have a crank rod bearing going in my '97 XJ, knocking somewhat loud. Started maybe 200 miles ago, how much long do you all think it will last?

Any experience with this?? Any quick remedy to quiet it down aka thick oil?

Jamie57

Could be the next 3 seconds or the next 2 years. Who knows? If it's knocking now you know it's on it's way. Just a matter of when.

Are you sure it's a rod knock? There is a very real possibility it's just a crack in the plate your converter bolts to. Or even the converter bolts themselves which have come loose. Lots of threads on this forum describing a rod knock type noise when that was the problem.
Drop the inspection cover and shine a flash light up there and check first.
Lot easier to fix and cheaper than dropping a crank and getting it ground.

ebelizard

I'm sure its the crank rod bearing; I took it to a mechanic to check it out and they drained some oil and screened it for metal shards....and they found shavings within the oil. So unless theres something else that could cause metal shavings in the oil....

Caish

For those that have never seen the internals of the engine.

This is the piston and rod assembly.
If your knocking is that loud, its not long till it goes away.
The rod bolts will typically start to stretch then brake then the rod violently gets slammed into the block and this known as throwing a rod. Its never good. Busted blocks, holes in the oil pan, bent valves, and even busted valves are the results.

IF its hammering that hard the damage is already done I would imagine and the only fix is pulling the engine and having the crank turned down if its not scored to bad, might even need a new crank.

When will it blow, no one can tell you that, its already knocking so there is all the warning your going to get. It will knock till it blows.

There is another knock in the engine, its called a wrist pin knock, it is generally never as loud as a rod knock, the wrist is pressed it to the rod and connects the piston to the rod. The wrist pin knock is a result of wear on the piston at the wrist pin. Engines can run for years with a wrist pin knock.

ebelizard

would wrist pin knock also contribute to metal shards in the engine oil?

Caish

Typically no.
If its audible knock, your dancing with the devil on how long it will last.
Its not a cheap fix if you can't do the work yourself.

RAH

same thing happened to my bossses truck last summer. we dropped the oil pan and put a set of bearings in and he is still driving it. the engine has over 315k miles. I would do it quickly though