Replace rod bearings as preventative maintenance


Old 09-29-10, 05:52 PM
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Replace rod bearings as preventative maintenance

Would it be good preventative maintenance to change the rod bearings of an engine at 100,000km intervals.
Just drop the pan and replace from the bottom
I was thinking why wait for bearings to get old and spin and take a connecting rod and crank with it.
I am thinking there must be a reason why it wont work because people dont do it.
But I can not figure out why it would not help an engine last longer
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Old 09-29-10, 06:28 PM
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Off the top of my head I would say it's because bearing replacement would require the crankshaft to come out and be machined. Much like you hone a cylinder wall when you replace the rings.

Also don't pistons need to be pushed out past the heads for that kind of work?
Good question but it's been awhile since I had an engine that "apart."
Old 09-29-10, 08:49 PM
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oy, will i be beaten up and chastised for this..
had it done twice. on an Oldsmobile and eclipse. on olds, kid seized engine driving on low oil. on our son's eclipse, we just did rings/head gasket/bearings at around 200 000 miles.
ok, now, here's the part i'll be beaten for. we did not remove crank shaft in either car. was no need to. journals where perfectly fine. bearings' low friction surfaces not so much. eclipse drove for another 60 000 miles, before we sold it. that olds, we not only un-seized the engine, but never had any complaints from the owner. and no, we did this via dropped oil pan in both cases, and on olds, pistons did not have to be removed or such. just cranked from the center bolt in crankshaft. it was tedious job, considering it was done in the street and in freezing rain.
now, bearings only, i really do not see that as a preventive measure. helps with oil pressure, but that's about it. what i do see as such, is to remove engine head, do the head, drop pistons down, and replace rings AND rod bearings same time. hone cylinder bores. by do the head, i mean clean cc-s, check on valves, remove valve springs and re-surface the valve seats, do valve stem seals, and resurface the head. i really don't want to get into how re-surfacing can be done by hand.
that's what we did on eclipse. stopped taking oil, got 2nd breath right away. 2 day slow pace job. total cost about $500 in parts.
Old 09-30-10, 03:55 AM
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I'll have to go with ukrbyk on this one. The rod bearings are probably not the first thing that will need replacement. Many more parts will fail before they will. Piston rings, cylinder walls, head, valves. I just think it is not a "preventive maintenance" item, but more a preemptive "rebuild", as everything should be done at once.
Old 09-30-10, 03:16 PM
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Why stop at “rod bearings”?

Preventive maintenance can be applied to:

Just to name a few.

Head gaskets
Intake manifold gaskets
Valve guides
Valve springs
Oil pumps
Rear mains
Water jackets
Intake valve
Exhaust valve

Do you see a pattern emerging here?

66 years of spinning wrenches has taught me:

Change your oil every 3000 miles.
Use only Castrol (organic) GTX Motor Oil.
Use only Purolator Pure One oil filters.
Remember, synthetic oil is “BS” and a waste of money.
Old 10-03-10, 07:28 AM
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replace rod brngs

This is some what of a common practice on heavy trucks or engines under heavy service. On a typical pass car not so much. For most people it is a job to get them to change oil. If you were going to give your daily driver with high milage to your teen ager it would be a great idea. I had a truck that ran under very heavy/dirty service,I changed the oil every 500 miles and brngs about every10K that motor ran for years and similar trucks would go thru an engine every year or so. This all hinges on the crank being in good shape.
Old 10-03-10, 12:30 PM
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I think I will, later on, get some rod bearings for $100 and change them with my next oil change.
I know when I worked on ships we would pull the caps and inspect them then retorque them.
I think as cheap as bearings are I could pull mine to take a look and put new ones in while im at it.
I cant see it doing any damage.
Someone chime in here if you can think of damage Im not thinking of.
I cant see any, ``wear in problems`, if the surrfaces look good.
I wonder how many main bearings I could slide in there while Im at it.
I drive an 06 Charger with 3.5 one hour and a quarter to work and then back again.
5 speed auto puts tach at 4 and 5 grand daily at times.
Oil and filter changed every 10,000 km (6,200 miles)

Old 10-05-10, 06:20 PM
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If you are going to pull the pan...sure, why not.

I changed out the rod bearings on my Grand Am with the 2.5 at 170K. I thought I was starting to hear the faintest light knock...almost like a wrist-pin but not sure....but very very faint at about 1200 no-load.

With the one rod bearing get a hammering on the crank..only takes a few thou to be bad. The bearings have a very thin layer that is against the will wear but generally it doesn't even touch the crank with the oil in between but over time it will wear....very, very minimal wear but rod bearings are easy once you are in the pan.

So I replaced the force balancer which was bad...and with the rods staring at me it was a 30 min job at that point. I plastigauged them and I don't remember what the gap was but they were all within spec but only within a thou or 2.

Get a set of standard bearings, you don't need to pull the crank. I wouldn't mess with the mains...if you pull the rear it may affect the oil seal but not sure on that model. Sometimes you can very carefully tap out the bearings from between the crank and the block but get someone that has done can very easily get into alot of trouble if you nick the crank.

If you change the mains do this one at a time and don't fully retorque the caps...may need to finish up with the proper torque sequence..again, I don't know that engine so check first.

100K is not alot of miles with regular oil changes. I personally prefer the Amsoil oil filter which has a synthetic media that does not affect flow as much when dirty...just personal preference...not an Amsoil war here...:Peeping On U2:

Good luck.
Old 10-07-10, 12:19 PM
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I wouldn't think you'd need to do it at 100K with a normal use car. I did it at 120K on a Porsche turbo that spends a lot of time at the track. The bearings were not in bad shape. I had worried because I bought the car used at 90K. 944turbos are known for spinning the #2rod bearing because Porsche drilled the hole in the crank on the wrong side for the #2. I have heard Chevy did this on their 454 originally. On the Chevy it was discovered when the 454 began being used for drag racing purposes. Centrifugal force prevents adequate oiling at high rpms at the drag strip. But in trucks, it was ok.

I don't know if it is necessary or not but I put the bearing caps on in the exact same position as they were in when I took them off. Mine may have individualized connecting rods/caps. They are forged; I know that much. It was also recommended that I replace the nuts on the caps. I did that. I also gauged the journals. They were within tolerance.

I had never done rod bearings before doing mine in 2002. Since then the car has been to the track 40 times or so. Must be ok.
Old 10-08-10, 08:05 AM
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Good answers above. I vote no because I think the chances of something going wrong is greater than any benefit with new bearings.

My only experience is rebuilding a 71 350 Olds motor. The bearings were slightly worn, but fine after 170K. The motor was rebuilt because the seals needed refreshing.
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