Rod bearing knock

[Terry Godbout]

We have an '06 Outback Limited with 74,000 1-owner miles on it. Recently an engine knock has developed. An independent mechanic and our local Subaru dealer have both diagnosed the knock as a rod bearing knock and both have said that a new short block is the best solution to the problem. At just under $5000, this is a stunner for a well maintained car with only 74,000 miles on it. Is this a common ailment for engines of this series? Could it be anything else?

[bratman18]

It's more common for the turbo models. But if the oil was low, or old, it can happen to the non turbos as well. $5000 is an insane price for that. But that's just my opinion.

[Terry Godbout]

$2400 for a new factory short-block, 16 hours labor, machine work on head, chain tensioner, etc. actual dealer estimate was $4700.

[bratman18]

You can buy a brand new turbo short block from subaru for $1800 so I'd imagine a non turbo is the same. And the rate they charge is outrageous. Machine work on the heads is less than $200. And there is no chain tensioner, unless it's an H6. All the parts for timing and the gaskets add up to less than $500.

[MilesFox]

Oil viscosity is something to consider. Although the cap may call for 5w30, you should use a 10w30 or 10w40 oil for summer temps, or at a 5w40 for all season temps. 5w30 really should only be used in winter temps.

 

Typical for bottom end failure is if the engine has been overheated on more than one occasion, or grossly overheated, say, if there was a HG failure before, or the HG is failing allowing coolant to escape and overheat from an air pocket in the cooling system.

[Fairtax4me]

Is it a 4 or 6 cylinder?

[farmer]

this is a stunner for a well maintained car with only 74,000 miles on it. Is this a common ailment for engines of this series?

 The mileage isn't always an indicator of the wear on an engine.  RPMs can wear out an engine on a low mileage vehicle.  That has to do with the in town or hill climbing that keeps the engine in the lower gears.  Vehicles that run open highways for extended intervals can have a lot more miles but less actual engine wear.

 

I would be cautious of a low mileage car from the center of New York City or Chicago.

 

In terms of viscosity of the oil you have to be careful with the heavier oils that would difficult to push through the bearings to get a flow that would cool the bearings.  Some of the engines that call for 00/20 have such small reliefs to hold the pressure in the bearings that a heavier oil with less flow through will actually heat up a bearing the low vis oils keep cool.

Edited September 1, 2014 by farmer

[MilesFox]

 The mileage isn't always an indicator of the wear on an engine.  RPMs can wear out an engine on a low mileage vehicle.  That has to do with the in town or hill climbing that keeps the engine in the lower gears.  Vehicles that run open highways for extended intervals can have a lot more miles but less actual engine wear.

 

I would be cautious of a low mileage car from the center of New York City or Chicago.

 

In terms of viscosity of the oil you have to be careful with the heavier oils that would difficult to push through the bearings to get a flow that would cool the bearings.  Some of the engines that call for 00/20 have such small reliefs to hold the pressure in the bearings that a heavier oil with less flow through will actually heat up a bearing the low vis oils keep cool.

Although this is true in general, subaru engines before the FA engines call for anything from 5w30 to 20w50, depending on climate. 

[farmer]

Yeah, I don't doubt that.  The older engines in other makes would use the 20-50 Valvoline racing oil for heat and pulling environments and that was thick stuff out of the can.  Seems like this 00-20 and 00-00 is all new gen stuff but it's been around awhile.  I thought it was more to help out on the government mandates on fuel economy.  For those I stick with the manufacturers recommendations pretty close.

[MilesFox]

I agree the 0w20 oil is part of fuel economy standards where a 5w20 or a 5w30 could substitute for a 2% hit in fuel economy. All in all, a subaru is limited to fuel economy by its overall gearing.

 

Personally, i would run 0w40 in a late model soob calling for 0w20 or 0w30. I advocate that 5w40 should be used over 5w30 in any of the ej or ea engines. I run 0w40 in both ej25d and ej22e.

[farmer]

I'll keep those oils in mind.  We haven't had a lot of Subies around here but we really like them.  My wifes new Forester really took care of our concerns with winter weather.  I've had to do fair amount of work on my 2000 Outback, but it's settled down to be a pretty reliable car.

 

I had wondered a little about the thin oils in some of these engines everytime I hear about a rod bearing problem.  Engineers can do a lot with the oil relief spec at a rod bearing and the pump volume, either to up the flow through or to build pressure at the bearing face.  Still, when I hear spun bearing or rod knock I think maybe the oil isn't quite right.  Out here you can't change the bearing spec, but you can change the oil.

Edited September 2, 2014 by farmer

[1 Lucky Texan]

there have been reports in older models of a rod-like sound due to bad belt tensioner letting the belt slap the inside of a timing cover. Might be worth inspect the inside of the cover for a rub mark or run the car and observe the belt. 

 

I'm just suggesting this out of hope. I suspect your mechanic has correctly diagnosed the issue - too bad, unusual in a car that hasn't been overheated.

[farmer]

Now that you bring that up, I just had a water pump bearing go out on a pump with less than 30,000.  The belt was slapping the cover and sounded like an internal engine noise.

[1 Lucky Texan]

Now that you bring that up, I just had a water pump bearing go out on a pump with less than 30,000.  The belt was slapping the cover and sounded like an internal engine noise.

 

weird coincidence! what brand was that waterpump?

[MilesFox]

there have been reports in older models of a rod-like sound due to bad belt tensioner letting the belt slap the inside of a timing cover. Might be worth inspect the inside of the cover for a rub mark or run the car and observe the belt. 

 

I'm just suggesting this out of hope. I suspect your mechanic has correctly diagnosed the issue - too bad, unusual in a car that hasn't been overheated.

This vid should give you an idea, although it isnt the one i was trying to find. For the tensioner, the forester should have the 'flapper' style tensiner in the ej25d and the ej251 engines, which have a higher failure rate than the log tensiners on ej22e and legacy ej25d engines. Something to consider. For the mileage vs the age, it would be worth servicing the timing belts to see if that cures the noise

 

[farmer]

That was a Gates, Lucky Texan.