Bad rod bearing, not a major problem?

[WisSubaru]

2008 Outback Wagon, just shy of 92K. Had cylinder head gasket issue at 60k (still pissed about that).

I've been getting a rattle during startup and when accelerating. Had the oil & filter changed at the Subaru dealership. 2 - 2.5 quarts low (yeah, I should check more often). Rattle diagnosed as rod bearing. Mechanic/manager said "It's not a big deal. Just feather the gas." Really? That sounds like terrible advice. I mean, yeah, I'll take it easy on the engine, I'm not a performance-type driver anyway. How long can I get by like this? Am I driving on borrowed time? Car performs well, it just has the rattle.

 

A buddy of mine who knows his way around an engine, though not Subies, said, "If the dealer isn't trying to bend you over for a major repair, maybe it's OK."

 

So, here I am, getting advice from you. 

Edited June 11, 2016 by WisSubaru

[Georg]

Hi,

Generally speaking, if a rod bearing (big end) is noisy it means there is metal contact between crank pin and the bearing.

As the bearing was designed for operation under hydrodynamic lubrication (that prevents metal to metal contact) it will fail very soon once it emits noticable noise.

 

If it really is a big end bearing failure there's no way to make a solid statement or even a guess on residual life as it massively depends on operating conditions, damage progress etc.

Typically a bearing failure ends up in either an engine seizure or a conrod exiting through the crankcase with subsequent potential oil leakage and fire.

 

 

However as you're calling it a rattling noise i have some doubts on this bearing theory.

There are some nice rod knock examples on Youtube you can compare with:

 

Edited June 11, 2016 by Georg

[gbhrps]

WisSubaru,

 

You may get lucky and the bearing will last the life of the car, or it may get progressively worse, seize and blow the rod through the block. Its a shame its happened to you at such low mileage.

 

It really comes down to how are the finances, when were you going to trade next, how much you can live without the car if it dies, how concerned you are about the issue, etc.? Myself, I'm just officially a senior citizen, have 5 other vehicles I can drive instead, and do all of my own mechanics. I'd be inclined to let it ride and find out if its going to be an issue. But I wouldn't be taking it on a cruise across the country far away from home. Good Luck!

[WisSubaru]

Thank you for the examples. Yeah, that sounds like what I have going on. I'll try to put up a sample of my rod knock here.

"...potential oil leakage and fire."  That would be a BAD day. 

 

Hi,

Generally speaking, if a rod bearing (big end) is noisy it means there is metal contact between crank pin and the bearing.

As the bearing was designed for operation under hydrodynamic lubrication (that prevents metal to metal contact) it will fail very soon once it emits noticable noise.

 

If it really is a big end bearing failure there's no way to make a solid statement or even a guess on residual life as it massively depends on operating conditions, damage progress etc.

Typically a bearing failure ends up in either an engine seizure or a conrod exiting through the crankcase with subsequent potential oil leakage and fire.

 

 

However as you're calling it a rattling noise i have some doubts on this bearing theory.

There are some nice rod knock examples on Youtube you can compare with:

 

[WisSubaru]

WisSubaru,

 

You may get lucky and the bearing will last the life of the car, or it may get progressively worse, seize and blow the rod through the block. Its a shame its happened to you at such low mileage.

 

It really comes down to how are the finances, when were you going to trade next, how much you can live without the car if it dies, how concerned you are about the issue, etc.? Myself, I'm just officially a senior citizen, have 5 other vehicles I can drive instead, and do all of my own mechanics. I'd be inclined to let it ride and find out if its going to be an issue. But I wouldn't be taking it on a cruise across the country far away from home. Good Luck!

We're shopping for a new car, but it's to replace the 03' Civic Hybrid with 180K+ miles on it. We may end up replacing the Subie instead. I have a 600-mile round-trip in July. I'd hate to ruin a vacation due to a mechanical problem. Dang. 

 

On a daily basis, I don't need a car at all, I can bike the short trip to work and to get around town, until the temperature drops to 10ºF.

[ccrinc]

I have to disagree with the above opinions.  Once a rod bearing starts to go, it will only continue until, ultimately, you will throw a rod and/or the engine wlll seize completely. . Also, that bearing material is circulating throughout your entire engine, doing its best to clog other oil passages (like to the cams).

 

This is not an "if", it's a "when".  The bearing is shedding material and it won't stop until it disintegrates completely.  Any mechanic who tell you "it's not a big deal" is a complete idiot or someone who just didn't want to address the problem.

 

The vast majority of the engines we build are due to being run low on oil or lack of oil changes and therefore, compromised rod and/or main bearings.  This is NOT a minor issue.  It is the death knell of the engine.  Period. 

 

ps: Don't even attempt a 600 mile trip with a bad rod bearing.  It will end in tears.

Emily