Myths and fallacies regarding egr and crankcase vent in TDIs that have both

I had removed the intake to replace the clutch on my alternator. Many
folks over at the tdi forum go on and on about the clogging of the
intake so I looked at mine. I had some crud so I removed it, scraped
it, sprayed it with carb cleaner and pressure washed it. It looked
pretty clean when done. No performance difference though. I guess it
was not all that clogged. I was planning on installing a Mann Provent
to reduce all that oil from getting in the intake. If any of you have
removed the intake pipe you will see all the oil which may not be all
that much but ti does accumulate over time. There are even articles
that mention how to clean the intercooler of this oil mess.

My theory is that the oil from the crankcase vent mixes up with the
egr gasses and the heat of the turbo to make some nasty coke or soot.
Removing the oil from the mix should reduce that build up. I need to
purchase a good vent to test my theory. Unfortunately it takes me
about 3 years to accumulate 100,000 miles.

One myth proposed is that reving the engine will prevent these
deposits. I generally drive for mileage getting 50 mpg regularly.
Reving over 3,000 is rather rare and I generally shift at 2,000. I
feel this is a myth because an engine is more often than not runnng at
relatively steady states at relatively low rpms with relatively low
boost. Second thought is that you have more crankcase pressure at
higher revs. More pressure might mean more oil slung about that gets
into the intake gunking stuff up. My third part of this is fluid
dynamics. There are areas of high velocity and low velocity in an
intake. You will get some deposits in areas of low velocity no matter
how much you rev.

Some propose egr recalibration which apparently has drwawbacks like
reduced power and reduced mileage. I believe I read that the computer
makes some calibration related to the egr that reduces fuel flow.

Has anyone seen any good studies from a well educated mechanic or
other source that might shed light on the oil-egr interaction?

Jim B.

My 2 cents: consider not fixing this thing at all. My one experience may be
a good data point if it is not a proper study or the opinion of a real
mechanic.

My '97 TDI has 171k miles and has had a clogged/bad egr valve since the
light came on at 62k. The check engine light came on during a roadtrip, and
the nearest dealer wanted $600 to do more than say it's the egr valve.

Since then I have gotten the same fuel economy as before; there is no more
black smokey exhaust than there should be (a black cloud appears under full
throttle acceleration and when it's cold); oil consumption has slowly
increased with advancing old age, but is still about 1/2 quart in 2k miles;
the check engine light finally burned out about a year ago. It's now all
good and I have no intention of ever looking into the matter further.

and by 'looking into the matter' I mean spend money.

My 03 tdi does not appear to use any oil between changes. 105,000
miles on the car. I change at 10,000 miles per manual. I need to send
in those oil samples someday.

Your story is interesting. I had my chip reprogrammed about 80,000
miles ago. It can be embarrasingly smokey but not as bad as chipped
Dodge or Ford.

I guess there are not many tdi people here.

"Keith Loyd" > wrote:

>My 2 cents: consider not fixing this thing at all. My one experience may be
>a good data point if it is not a proper study or the opinion of a real
>mechanic.
>
>My '97 TDI has 171k miles and has had a clogged/bad egr valve since the
>light came on at 62k. The check engine light came on during a roadtrip, and
>the nearest dealer wanted $600 to do more than say it's the egr valve.
>
>Since then I have gotten the same fuel economy as before; there is no more
>black smokey exhaust than there should be (a black cloud appears under full
>throttle acceleration and when it's cold); oil consumption has slowly
>increased with advancing old age, but is still about 1/2 quart in 2k miles;
>the check engine light finally burned out about a year ago. It's now all
>good and I have no intention of ever looking into the matter further.
>
>and by 'looking into the matter' I mean spend money.
>

Jim B.

Keith Loyd > wrote:
> My 2 cents: consider not fixing this thing at all. My one experience may be
> a good data point if it is not a proper study or the opinion of a real
> mechanic.

> My '97 TDI has 171k miles and has had a clogged/bad egr valve since the
> light came on at 62k. The check engine light came on during a roadtrip, and
> the nearest dealer wanted $600 to do more than say it's the egr valve.

> Since then I have gotten the same fuel economy as before; there is no more
> black smokey exhaust than there should be (a black cloud appears under full
> throttle acceleration and when it's cold); oil consumption has slowly
> increased with advancing old age, but is still about 1/2 quart in 2k miles;
> the check engine light finally burned out about a year ago. It's now all
> good and I have no intention of ever looking into the matter further.
> and by 'looking into the matter' I mean spend money.

Nice attitude. The purpose of EGR is not to affect your fuel economy or
power (although a malfunctioning one could affect both) but rather to
reduce emissions. In fact, unlike a catalytic converter it isn't designed
to reduce all emissions, just one type, oxides of nitrogen (NOx). While
diesels are very clean in terms of hydrocarbon and carbon monoxide
emissions they are *WAY* dirtier than gasoline engines in terms of NOx
emissions, by a huge margin.

If you want to run a car with poorly functioning emissions control
equipment, fine, that's your selfish choice. Personally, I think anyone
who feels it neccessary to buy a car should be willing to take on the
responsibility (financial and otherwise) of properly maintaining it but
apparently you don't feel that responsibility. If you don't want to
pay $600 for the dealer to replace the valve, why don't you do it
yourself? Please don't advocate other people engage in irresponsible
behavior.

As for the light "burning out", thats a pretty incredible statement. The
MTBF of an LED is probably around 100k hours. Assuming you were driving
at 30 mph, for 110k miles, that'd be less than 4000 hours. Those LEDs
should easily last well longer than the life of the car, which without
having the benefit of the light might not be all that long anyway.

The EGR does other things besides help with emissions. And one important
thing the EGR does on the TDI is make the engine smoother by removing the
slam bam of the diesel firing at TDC by introducing a lot of exhaust gas
into the mix. And the exhaust gas effectivly reduces the volatility of the
gas charge in the cylinder. This drags the burn cycle out a bit and makes
the engine run smoother. Smoother means more people considered it , as an
alternative to a gas engine. However if you reduce the charge , the gas
milage reduces too. VW got away with it because the TDI pumps run a higher
fuel pressure and Direct injection is more efficient then the old pre
chamber injection. And although I complain about VWs a lot no one can say VW
didn't do their homework on getting a TDI to run smooth. My personal opinion
is that the less exhaust gas you recycle the better gas milage you get. The
rougher your car will run, and it will run hotter too, because your gas
charge is hotter . but you also pollute the atmosphere more too. Also you
get less buildup or crud in your intake also. VW fixed a problem with
emissions , and vibration. {Refinement} by using an EGR where none was
necessary, temporarily, caused by crappy diesel fuel in the US. But now
that the fuel problem will soon be fixed, and the EGR won't cut it anymore ,
and VW doesn't want to design a diesel from scratch, because theres not
enough market here for them, the diesels will soon be withdrawn. Problems
solved. I,ve not taken a VW egr apart , but every other one I,ve taken
apart is crudded up, and is tuned by installing the correct size washer to
reduce exhaust flow to the required amount.
"nothanks" > wrote in message
...
> Keith Loyd > wrote:
>> My 2 cents: consider not fixing this thing at all. My one experience may
>> be
>> a good data point if it is not a proper study or the opinion of a real
>> mechanic.
>
>> My '97 TDI has 171k miles and has had a clogged/bad egr valve since the
>> light came on at 62k. The check engine light came on during a roadtrip,
>> and
>> the nearest dealer wanted $600 to do more than say it's the egr valve.
>
>> Since then I have gotten the same fuel economy as before; there is no
>> more
>> black smokey exhaust than there should be (a black cloud appears under
>> full
>> throttle acceleration and when it's cold); oil consumption has slowly
>> increased with advancing old age, but is still about 1/2 quart in 2k
>> miles;
>> the check engine light finally burned out about a year ago. It's now all
>> good and I have no intention of ever looking into the matter further.
>> and by 'looking into the matter' I mean spend money.
>
> Nice attitude. The purpose of EGR is not to affect your fuel economy or
> power (although a malfunctioning one could affect both) but rather to
> reduce emissions. In fact, unlike a catalytic converter it isn't designed
> to reduce all emissions, just one type, oxides of nitrogen (NOx). While
> diesels are very clean in terms of hydrocarbon and carbon monoxide
> emissions they are *WAY* dirtier than gasoline engines in terms of NOx
> emissions, by a huge margin.
>
> If you want to run a car with poorly functioning emissions control
> equipment, fine, that's your selfish choice. Personally, I think anyone
> who feels it neccessary to buy a car should be willing to take on the
> responsibility (financial and otherwise) of properly maintaining it but
> apparently you don't feel that responsibility. If you don't want to
> pay $600 for the dealer to replace the valve, why don't you do it
> yourself? Please don't advocate other people engage in irresponsible
> behavior.
>
> As for the light "burning out", thats a pretty incredible statement. The
> MTBF of an LED is probably around 100k hours. Assuming you were driving
> at 30 mph, for 110k miles, that'd be less than 4000 hours. Those LEDs
> should easily last well longer than the life of the car, which without
> having the benefit of the light might not be all that long anyway.
>
>
>