[A4] dead 2001 A4 1.8Tq
tyson at up-times.com
Tue Apr 1 11:29:28 PDT 2008
Robert, I thought this way too until I experienced catastrophic oil
failure on a turbo car for the 4th time. What most people don't realize
is that oil filters only filter 1-10% of what passes through them - the
rest goes around via an overflow valve. Think about how thick oil is and
how much pressure it would take to push it through that paper membrane.
If oil filters filtered 100% of the flow, they would have to be a lot
less restrictive and oil a heck of a lot more liquid.
The idea is that under normal operation there are very few contaminants
and the filter will eventually pick them up - it is only a problem when
the contaminants build up someplace and block flow. In a situation like
a crank-walk there is so much metal crap that goes everywhere that the
filter is clogged before you have ANY indicators and then pretty much
all oil goes around the filter and through the overflow valve.
If metal bits were found with the naked eye in this guy's oil and he
drove the car until it pretty much stopped, there is no way that the
turbo has survived. Amazingly enough, even with that much crap in the
oil, the engine will run and pull fine until lack of lubrication causes
an overheat. The power loss that he described was most likely the turbo
coming to a screeching halt due to the bearings being packed with debris
at which point the turbo impeller will cause a blockage in the intake
path - significant power loss...
I would totally tell this guy to do more research - $9k for that much
work is outrageous! But he does not sound like the mechanical type - he
will get his pants pulled down everywhere. And if he gets an
"independent" mechanic to do this, he might lose $5 in parts and labor
as well as weeks and months of downtime for his car just to have other
issues down the road from this non-warranteeied work... At this point, I
think that he is better to cut his losses, get a few grand for a car,
get another one and remember to change oil more frequently.
Technical Director, Uptime Technical Solutions LLC.
tyson at up-times.com
From: Robert King [mailto:gt40mkii at gmail.com]
Sent: Tuesday, April 01, 2008 11:18 AM
To: Tyson Varosyan
Subject: Re: [A4] dead 2001 A4 1.8Tq
On Tue, Apr 1, 2008 at 1:10 PM, Tyson Varosyan <tyson at up-times.com>
> Yea, if there are metal bits inside the oil, you pretty much have to
> replace everything that was touched by it - turbo included.
Hang on -- Explain how the metal bits in the oil got into the turbo...
There's a filter between the oilpan (where the metal bits are,) and
the turbo (and everything else.) It sounds like you're assuming there
was also a filter failure, too, which IMHO, is a bad (and expensive,)
Don't do ANYTHING until you have the engine torn down and inspected,
and that includes the oil in the turbo, and the oil filter!
If the filter is OK, I wouldn't replace anything that came into
contact with the oil other than the oil pump.
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