Symptoms of worn main and rod bearings

[cecil hollifield]

I have a 2004 Kia with a 6 cy engine with 164000. Bought used at 10,000. I have keep regular maintenance by changing the oil and filters as recommended. My wife complains of it making a loud “roaring” sound. To me, it starting to sound like a bearing problem. I have owned older auto and am familiar with a “thumping” sound of bad rod and main bearings. In one of your videos, you talk about oil pressure and how there is a layer of oil between the bearings and the shaft. Is there a way to check the main and rod bearings without pulling the engine?

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[Andrew Button]

Get an automotive stethoscope. Probe around the bottom of the engine. Listen for a deep noise. See if the noise increases with RPM and gets deeper, you are on the right track.. Drive the car and go up a hill slowly and try to lug the engine, this will increase the sound of a ROD bearing. If you don’t have a stethoscope, putting your ear to the end of a long screwdriver and pressing around engine can work, but is very uncomfortable. I can actually hear the difference between a lifter and rocker arm this way, but its not the best. There are other ways of diagnosing this, but this is how I would start. Some cars the pan can be pulled with engine in car, but thats alot of work. I am sure there are others here with ideas that are better than mine but that is my two cents worth.

[Gary]

Oil pressure is also a good indicator. If you plug in a gauge and the pressure is consistantley low, there may be a rod bearing issue. Typically, when the engine is warm the rod knock will get worse as the oil thins out. The pressure can drop drastically at this point.

[cecil hollifield]

Thanks, That was my thinking. Do you know what a good pressure reading would be for a 2004 Kia 6 cy.?. The car is in good shape and I really don’t want to get rid of it, but I really don’t want to rebuild the engine either. Can a worn muffler have that sound? I put my foot on the break and increase RPM as AndrewButton442 (to Lug the engine)suggested and it doesn’t get any worse.

[Gary]

[quote=”cb1945″ post=124181]Thanks, That was my thinking. Do you know what a good pressure reading would be for a 2004 Kia 6 cy.?. The car is in good shape and I really don’t want to get rid of it, but I really don’t want to rebuild the engine either. Can a worn muffler have that sound? I put my foot on the break and increase RPM as AndrewButton442 (to Lug the engine)suggested and it doesn’t get any worse.[/quote] Intresting, honestly without hearing the sound myself, it’s hard to give a definitive answer. Anyways, oil pressure should read 50-60 psi when cold and 25-40 psi when idling warm. A good rule of thumb is for every 1000 RPMS there should be at minimum 10 psi increase more or less.

[Gary]

I forgot to mention,there is a sure fire way to tell the condition of your engine. I will send you a link to a place I use regularly for oil analysis: http://www.blackstone-labs.com/

They will send you a free kit and then it’s 25 dollars for the analysis. It is worth it because they give you a report card for your engine. Their site also has some useful info as well.

[Andrew Button]

You have to lug it under load- up a hill, in highest gear possible. This is easier to do with a manual trans as an auto will want to kick down to a lower gear which will raise rpms and not lug the engine. A good rule of thumb is 8 to 10 lbs of oil pressure per 1000 rpm, although look for a generally low reading regardless. Watch for super low numbers at idle – drifting lower as oil temp increases. I had a turbo nissan that would damn near drop to zero on the highway rapid slowdown when hot, but it never hurt anything, oddly enough. Change the oil if its not fresh. Can a loud muffler cause funny noises, definatly. Look for rust and or holes in the system. Especially farther back

[cecil hollifield]

Thanks guys. That’s like taking a blood sample and checking for problems. That’s cool..
I ‘try that .. let you know.. I’ll try the uphill under load. It’s an auto, but it has a manual shifter… Thanks again

[Gary]

[quote=”cb1945″ post=124195]Thanks guys. That\’s like taking a blood sample and checking for problems. That\’s cool..
I \’try that .. let you know.. I\’ll try the uphill under load. It\’s an auto, but it has a manual shifter… Thanks again[/quote] Your welcome, keep us posted.

[Rereonehundred]

My usual sound diagnostics for crank mains or big-ends are knock at high loads.

Worn wrist pins give a double-rap upon deceleration.

And piston slap, is a slap.

But most of my experience is on air cooled motorcycle engines. I’ve never worn out a car engine. Bodies always fall away first.

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