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VW MKIII-A3/B4 TDIs This is a discussion about MKIII-A3/MkIII Jetta/Golf (<99.5) and B4 Passats (96,97) TDI's. Non TDI related postings will be moved or removed.

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Old October 25th, 2006, 11:43   #1
Rickstah
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Join Date: Feb 2002
Location: Yukon, Oklahoma
Fuel Economy: 51/45/41
Default Typical Life of AHU rod bearing?

I'm about to have the head redone, and my mechanic is lobbying for me to have rings and rod bearings done. Christine consumes some oil...about half to one quart per 10k oil changes...sometimes less if I don't drive the mess out of it. I'm thinking the labor to put rings in, since the head is off, would be nominal, but the rod bearings, they really push the price up since he has to drop the pan, etc...I've actually never had a rod bearing go out on any vehicle...could I safely let those be at 144K?
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Old October 25th, 2006, 12:45   #2
Chris Bell
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Your oil consumption is good and normal for this engine.

There should be no additional labor cost to replace the rod bearings; replacing the rings requires dropping the pan and unbolting the rods.
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Old October 25th, 2006, 12:53   #3
Rickstah
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ok, I was not thinking that through, I guess....thought one could just rotate the motor up until the piston stuck out above the block...so you have to drop the pan either way. So I guess the question is, should I be concerned about the rings getting worse after larger nozzles go in and I begin pushing it harder? Thanks for the info.
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Old October 25th, 2006, 14:21   #4
dzlnator
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I would replace the rod bearings. They are cheap and you get back new clearances. If the bearings show no "brass or copper tint" you are not worn, however, if you are into the the "brass" I would definitely replace them.
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Old October 26th, 2006, 04:34   #5
Chris Bell
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Quote:
Originally Posted by Rickstah
So I guess the question is, should I be concerned about the rings getting worse after larger nozzles go in and I begin pushing it harder? Thanks for the info.
The issue is not larger nozzles, but rather age and mileage. Its safe to say that cylinder leakage and oil control will not improve after 144K, and will eventually get worse. But having said that, with diligent maintenance and favorable operating conditions, you might go another 144K before compression and oil control are reduced.

Have your mechanic measure cylinder bore taper and roundness. Proper technique is to use a dial bore gauge or inside/outside mic., not just feeling the ring ridge. Taper will probably be minimal, but make sure its checked because if it is significant, re-ringing would be a waste of time...and oversize pistons would be the correct solution. Again, pretty unlikely at your mileage.

The concern I have about re-ringing with the block remaining in the car is the preparation. Re-ringing requires breaking cylinder wall glaze and removing the ring ridge, if any. Both of these procedures require carefully sealing the bottom of the cylinder so that abrasive (from the glaze-breaking honing mandrel or Flex-hone), metal, lubricant, solvent, and soap & water don't enter the crankcase. Needless to say, the whole process should be done meticulously.

Cylinders honed in a honing machine (block out of the car) are brushed with solvent, then washed with soap & water and bore brush TWICE, and sometimes there is still imbedded micro grit remaining in the "cross-hatching" of the cylinder wall. A white paper towel wiped throughout the cleaned and dried cylinder shouldn't show the slightest trace of brown. Light glaze-breaking honing with block in the car produces much less grit, but impeccable cleaning (and cylinder bottom sealing) is still a must.
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Last edited by Chris Bell; October 26th, 2006 at 04:48.
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Old October 27th, 2006, 12:07   #6
rallymerkur
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Quote:
Originally Posted by Chris Bell
Your oil consumption is good and normal for this engine.

There should be no additional labor cost to replace the rod bearings; replacing the rings requires dropping the pan and unbolting the rods.
And replacing the rod bearings doesn't require you drop the pan.
I'd say if you're going to replace the rod bearings, might as well do the rings too.
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Old October 28th, 2006, 05:32   #7
Chris Bell
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Dropping the pan required for rings or bearings. Rickstah's original question was: if replacing the rings, should bearings be replaced since he thought ring replacement did not require dropping the pan.
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Last edited by Chris Bell; October 28th, 2006 at 05:35.
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Old October 28th, 2006, 06:17   #8
Frank M
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Default why?

Why does the head need to be redone?
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