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Loud Clicking / Main Bearing Burnout?
04-11-2011, 03:56 PM
Post: #1
Loud Clicking / Main Bearing Burnout?
Hi All -

I'd really appreciate any insight you can share.

I drive a 2005 Subaru Legacy, 4 Cylinder, Automatic Transmission.
I live in San Francisco, CA, but this season we've made several trips to Tahoe and have been driving in the snow w/ some frequency.

Yesterday, 2 hrs into the drive, the acceleration just cuts out - and, this loud clicking noise starts. The noise remains without accelerating, but goes away in neutral and gets louder/faster upon acceleration.

I took it to the shop this morning and they said - well, you have no oil. Okay, fine - but we do have an oil indicator light and while it has flashed once or twice, it certainly hasn't remained on for any duration of time. I mentioned that and he said that it came on when he turned the car on, so they'd try that first.

I just got a call back saying that adding oil didn't solve the problem and they think the bearings have burned out and we need to replace the motor.

I'd love to just get a read as to whether or not this makes sense. It seems like a pretty huge leap from driving around w/o any trouble at all to replacing the motor entirely and a full bearing burnout (which, admittedly, I don't even understand what that means).

We did have to replace the wheel bearings recently. But that is all the work that we've had to do to date on this car.

Help, please.

CJ
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04-11-2011, 05:02 PM
Post: #2
RE: Loud Clicking / Main Bearing Burnout?
Your mechanic is likely correct. There is a reason that mechanics call the Oil Pressure Indicator Light an “Idiot Light.” By the time that the light comes on it is pretty much to late.

The bearings that he is talking about are the “Engine Bearings.” The crank shaft rides in “Main” bearings, the pistons are attached to the crank by “Rods” and “Rod Bearings.” Ideally, oil is pressurized to provide a thin, protective barrier between the bearings and the crank. All these parts are moving fast and under great pressure. By the time the pressure gets low enough to turn the light on you better turn the engine off and get some oil in it before restarting. Better yet, that is the reason for regular maintenance, checking and changing the oil, filters, etc. Sorry, but this is likely a very expensive lesson as to why it is cheaper to do regular service work.

Thanks for using the forum,
Garner

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04-11-2011, 07:08 PM
Post: #3
RE: Loud Clicking / Main Bearing Burnout?
Thanks for the quick response and help.

An expensive lesson indeed!

*sigh*


(04-11-2011 05:02 PM)Garner Wrote:  Your mechanic is likely correct. There is a reason that mechanics call the Oil Pressure Indicator Light an “Idiot Light.” By the time that the light comes on it is pretty much to late.

The bearings that he is talking about are the “Engine Bearings.” The crank shaft rides in “Main” bearings, the pistons are attached to the crank by “Rods” and “Rod Bearings.” Ideally, oil is pressurized to provide a thin, protective barrier between the bearings and the crank. All these parts are moving fast and under great pressure. By the time the pressure gets low enough to turn the light on you better turn the engine off and get some oil in it before restarting. Better yet, that is the reason for regular maintenance, checking and changing the oil, filters, etc. Sorry, but this is likely a very expensive lesson as to why it is cheaper to do regular service work.
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04-11-2011, 09:37 PM (This post was last modified: 04-11-2011 09:48 PM by Rupe.)
Post: #4
RE: Loud Clicking / Main Bearing Burnout?
Would agree with Garner and since this will probably be expensive I'll expound a bit further so you will fully understand what happens.

Think of the oil as a milk shake in a big cup. You enjoy it's smooth taste till it starts to get low. As you near the bottom you start sucking air up the straw. Still tastes pretty good, right? You are still getting something up the straw, right? OTOH, it's not as filling with all that air.

Back to the oil issue.... the engine enjoys that smooth feeling and will continue to suck up the last drop but that pesky oill pressure sensor doesn't know there's all that air mixing in with the oil so doesn't turn the light on.... till it's all gone! In the meanwhile all I can say is "air does not lubricate" and keep it simple. That is why they invented the dip stick, which should be checked on a regular basis.

BTW, that oil pressure sensor only watches for the minimum pressure, or about 10 pounds. It's connected to a warning light but you only have a few seconds to react at best. Normal pressure in a healthy engine much higher.

Bottom line is without oil pressure (that's pressure without air bubbles) damage will be done. One would need to do a full tear down to diagnose exactly what can be saved and what needs replacing, which these days is likely more costly than just replacing the engine and having a factory warranty. (OEM or aftermarket)

Good luck and let us know what you decide to do as it may help others reading these pages.

Edited to add: That first sign of ticking was probably the air circulating to the valve lifters. Since they are hydrolic they rely on oil for their automatic slack adjustment. When air gets into the system (low oil?) it compresses more easily so you are hearing valve noise. Since that engine is what they call "over head cam" you start to get damage on the cams fairly quickly. If you want a second opinion on the damage all you need to do is drain the oil into a small container and shine a light on it. If you see a metalic glitter then you are looking at fine metal particles from inside the engine, which is a sure sign of trouble.
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04-11-2011, 10:37 PM
Post: #5
RE: Loud Clicking / Main Bearing Burnout?
Thank you, thank you! again!

I appreciate the additional analysis. It seems that we will be replacing the engine entirely with another used 4 cylinder.

I'll be happy to continue to post throughout the process, sheepishly though - considering if we'd just kept the oil fresh none of this would be an issue. :-)
(04-11-2011 09:37 PM)Rupe Wrote:  Would agree with Garner and since this will probably be expensive I'll expound a bit further so you will fully understand what happens.

Think of the oil as a milk shake in a big cup. You enjoy it's smooth taste till it starts to get low. As you near the bottom you start sucking air up the straw. Still tastes pretty good, right? You are still getting something up the straw, right? OTOH, it's not as filling with all that air.

Back to the oil issue.... the engine enjoys that smooth feeling and will continue to suck up the last drop but that pesky oill pressure sensor doesn't know there's all that air mixing in with the oil so doesn't turn the light on.... till it's all gone! In the meanwhile all I can say is "air does not lubricate" and keep it simple. That is why they invented the dip stick, which should be checked on a regular basis.

BTW, that oil pressure sensor only watches for the minimum pressure, or about 10 pounds. It's connected to a warning light but you only have a few seconds to react at best. Normal pressure in a healthy engine much higher.

Bottom line is without oil pressure (that's pressure without air bubbles) damage will be done. One would need to do a full tear down to diagnose exactly what can be saved and what needs replacing, which these days is likely more costly than just replacing the engine and having a factory warranty. (OEM or aftermarket)

Good luck and let us know what you decide to do as it may help others reading these pages.

Edited to add: That first sign of ticking was probably the air circulating to the valve lifters. Since they are hydrolic they rely on oil for their automatic slack adjustment. When air gets into the system (low oil?) it compresses more easily so you are hearing valve noise. Since that engine is what they call "over head cam" you start to get damage on the cams fairly quickly. If you want a second opinion on the damage all you need to do is drain the oil into a small container and shine a light on it. If you see a metalic glitter then you are looking at fine metal particles from inside the engine, which is a sure sign of trouble.
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04-11-2011, 10:43 PM
Post: #6
RE: Loud Clicking / Main Bearing Burnout?
By all means, please do!

Education is an on going process.
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