are my rod bearings worn?

i have been hunting down a knock in my engine that only has 111,000 miles. i had to do the rear main seal as well so i figured i would kill two birds with one stone and check the rod bearings. while looking at the bearings there seems to be no up or down movement just side to side on all pistons. is this normal? what should i look at while i have the oil pan off?

what kind of "knock" are we talking about?? when do you hear it? unless your bearings are totally shot you really wont tell just by looking at them..

can you tell where in the motor the knock is comin from(top, bottom, frt or back) also does it do it whn the motor is cold or up to running temp?

The side to side is normal,there needs to be room for the rods to move on the journel,pull a cap and check the condition of the bearing.Or better yet use plastiguage and check the clearence.
Wayne

it is a loud knocking when the engine starts and runs at idle. it is so bad i dont want to drive it. it sounds like it is comming from the head but then i go under and it ounds a little louder in the pan do i took the rockers and fulcrums off and checked all the push rods and they were all good wverything was torqued to spec. cant tell if it is front or back. i took the ingition wire off the distributer and crancked the engine over and couldnt hear anything. i am stumped???

any ideas? i still cant figure it out:dunno:

Is it a rhythmic rapping, or more like the clatter of a diesel? If the latter, it might be piston slap, a common occurrence on 4.0's. Some do it badly, some a little, some not at all. But you should also check pulleys and water pump, which can sound almost exactly the same. If you already have slap, a bad water pump can sneak up on you.

how do i check piston slap?

Piston slap often seems to be worse on a cold motor, connecting rod bearings sometimes knock worse when the engine heats up and the oil gets thinner.
If you pull a piston connecting rod cap off and gently move the piston up and look at the bearing sleeve, you can often see excess wear, as the brass coating under the chrome coating on your connecting rod bearing. Often near the top center bearing (sleeve) half. If the bearing is worn through the chrome coating to the brass coating, it's likely toast.
But plasti gage will tell you for sure.
I plasti gage every new bearing, before tightening the cap down for the last time. I don't trust the markings on the box or the bearing.
A short piece of plastic tubing put to your ear and various parts of the motor really helps narrow down the loudest point of the knock and the likely cause.
Worn connecting rod bearings (among others) will also often show up as somewhat lower oil pressure. If your oil pressure is slowly dropping and the motor is getting slowly louder, connecting rod bearings are a possibility. It's likely the mains may also be worn, but they often seem to last longer than the connecting rod bearings in my experience.

Could it be a stuck valve lifter? If it is I would try som engine cleaner that mix in the oil. It will remove crud and dirt stuck in the lifter.

Piston slap is common on these engines.

regards
Torfinn

Nobody can tell you specifically where it is. Based on an accurate description of the knock your hearing, an experienced mechanic--one whose repaired a number of knocking engines--can give you an educated guess of what might be loose; example: "rod bearings typically are "double knocks, increasing in frequency and intensity as the engine reves, especially when warmed up", or "single, lower frequency knocks could be main bearings", etc. Bottom line, a knocking rod bearing will have slop in the bearing, just like a knocking main bearing. Use plstigauge to check clearance on each bearing. Of course, you've already checked all accessories to insure there OK, right? Also, at idle, I've heard a number of "knocks" caused by exhaust pipes hitting something; often sounds like a rod bearing, but normally disappears when the engine is reved. A better description of what your hearing, including temperature of engine, oil pressure, affect of reving the engine on the knock will allow a better guess. Also, probably good idea to run a compression check.

ok so i checked everything in the lower end and couldnt find anything wrong. tried listening to the water pump and that was good. so we put everything back together and ran it, while it was ticking i took the oil cap off and noticed that the rocker arm was moving in tune with the ticking so i am going to try replacing everything in the head. thanks for everybodys help

swany said:

ok so i checked everything in the lower end and couldnt find anything wrong. tried listening to the water pump and that was good. so we put everything back together and ran it, while it was ticking i took the oil cap off and noticed that the rocker arm was moving in tune with the ticking so i am going to try replacing everything in the head. thanks for everybodys help

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Is the ticking the same noise you stated previously as a knock? If so, sounds like you have dirty or worn lifters. Not uncommon for an engine with over 100K mile. Generally, worn lifters will tick at hot idle, but quite down when the engine is reved up a little. Worn lifters and low oil pressure equal ticking that's constant at idle. I'm afraid you'll have to pull the head to replace the lifters.

You have to realize that old motors make noise. They rattle, they moan, they tick, they knock, they whine. Just like old men (me especially). The tough part is determining if the noise is normal for the age and mileage, or is a symptom of something bad happening (or about to happen).

My stock '88 (165K) has noisy lifters, noisy injectors, a bit of piston slap, doors that squeak, power windows that moan and more. Oil pressure is good, temps are normal, runs great.

Certainly, diagnosing a "noise" in here is difficult since no one else can hear it. As xjbubba suggested, you might try to find someone who can steer you in the right direction based on the sounds yours is making.

ok so its fixed :yelclap: changed out the rockers fulcrums and bridges no more knock. i know it is usually ticking that you hear in the head but this was wicked loud knocking like it was going to blow up. but it is all gone. thanks for all the valuable info it was a good education.