...OIL LEAK AT OIL-FILLER CAP of ALH engine...

[MrSafety]

I have a problem leak from around the Oil-Fill Cap !
I have changed the cap at least 3 times and the latest one was new!
So I figure that the crankcase pressure is somehow building up too much either:
(a) because we have an engine that has too much "blow-by"… OR
(b) there are 1 or more restrictions in either the "Hockey Puck-Like"
....... filter that sits on the valve cover … OR
(c) a restriction in the "Breather Hose" that runs between the “Puck" and
....... its connection to the "Intake Air Tube" just before it turns down
....... behind the engine on it's way to the turbocharger… OR
(d) there is too little suction (in general or at certain times) from the turbo ....... charger
My Bentley printed manual calls this the Positive Crankcase Ventilation (PCV) system...
but I also see on this FORUM where many call this the "CCV" system which I presume is short for
"CrankCaseVentilation" system!
I have:
(1) verified that the "Hockey-Puck" filter/separator is not restricted...
(2) verified the “Breather Hose” and it’s connection to the “Intake Air Tube”
..... are not restricted…
(3) there is observable suction of air into the “Breather Hose” when the
..... engine throttle is increased
(4) verified the presence of a 2-wire electrical component at the connection
..... of the “Breather Hose” to the “Intake Air Tube”… and that this appears to
..... be a heater as explained in the Bentley Service Manual.
(5) verified that with the Oil-Fill Cap in place, the crankcase is pretty much
..... air tight when I try to blow air in through the hole in the valve cover that
..... the PCV/CCV “Hock-Puck” draws oil mist and vapors.
I am aware of what is known on this FORUM as the “CCV Mod” whereby an alternative
Oil Mist Separator/Filter is installed on the engine as a means to reduce the buildup of oil residue
on the walls of the intake manifold… but our engine has no such system installed.
Today I replaced the “Hockey-Puck” Filter-Separator in a somewhat desperate attempt to solve this mystery!

Q1 – What is the purpose of the “heater” installed at the connection of the “Breather Hose” to the
....... “Intake Air Tube”?
Q2 – In response to (5) above, should there be an air inlet opening to the
...... crankcase somewhere so that more air is Freely drawn through by the
...... turbo charger’s suction on the Intake Air Tube”?
Q3 – Is it possible that somehow there is a partial loss of turbo suction
....... under certain conditions and this results in insufficient suction and thus
....... the pressure builds up in the crankcase?
Q4 - How does one test to see IF excessive "blow-by" is happening...
...... a compression test?
Q5 - Does anyone have a suggestion as to what I look into next?
Any help will be most appreciated!
Sam Ross

[KLXD]

There is moisture in the blow by gas. The heater keeps it from freezing and blocking flow.

It's not a positive CV system since there is not an inlet to the crank case as on most gas engines that lets filtered air flow through it.

A compression test might be in order.

Is the sealing surface on the valve cover undamaged? Wrong cap?

Any large vacuum leaks? The discharge from the vacuum pump is into the case but there should be no flow from it except a very minor amount when a vacuum device is operating. Even if there were the flow path to the manifold is so big I can't see the crank case pressurizing.

[MrSafety]

Originally Posted by KLXD

There is moisture in the blow by gas.
The heater keeps it from freezing and blocking flow.
It's not a positive CV system since there is not an inlet to the crank case as on most gas engines that lets filtered air flow through it.
A compression test might be in order.
Is the sealing surface on the valve cover undamaged? Wrong cap?
Any large vacuum leaks? The discharge from the vacuum pump is into the case but there should be no flow from it except a very minor amount when a vacuum device is operating. Even if there were the flow path to the manifold is so big I can't see the crank case pressurizing.

Thanks a lot for your response and I'm already on much the same page
as you when it comes to understanding the distinct differences between
the PCV system on a GAS engine and what Diesels have.
I'll check into and try to monitor our TDI's vacuum system.
Q1 - Do you suppose that modifying and making the TDI's CCV system have a small continuous flow of filtered outside air
introduced into the crankcase... might this make the CCV more "dynamic"/self purging and less likely to build up pressure?
[edit]IF I were to do this, then I would definitely look seriously at the "CCV-Mod" ideas I found on this FORUM.
As I understand these "CCV mod" ideas, they are an attempt to reduce the CCV/EGR systems
from causing the "goo" that forms on the inside of the intake manifold!
Also, someone has made a strong case with me to double up on the
flat/round gasket seals used on the underside Oil-Filler Cap.
They gave me the P/N for this $1-to$2 gasket seal... 06A-103-483-D!
I'll install two of these and see IF this easy fix works!?!
Thanks and I'll report back by next week!
The car belongs to my Son!
Sam Ross

[Ski in NC]

Cap should not leak even if blowby flow is high. Something is wrong with cap sealing. Aftermarket cap??

Redneck blowby flow test: with engine running, loosen oil fill cap see if it tries to blow off. It should just "dance" as there are normal pressure pulses in crankcase. But if on loosening it blows out of your hands and hits the hood, you've got a problem. If it just sits there and dances, you have a good engine and a bad sealing cap.

[KLXD]

A bleed wouldn't work. Unlike a gas engine where the PCV outlet is plumbed downstream of the throttle plate, there is virtually no vacuum in the TDI intake system unless the filter badly plugged.

[MrSafety]

Originally Posted by Ski in NC

Cap should not leak even if blowby flow is high. Something is wrong with cap sealing.
Aftermarket cap??
Redneck blowby flow test: With engine running, loosen oil fill cap see if it tries to blow off.
It should just "dance" as there are normal pressure pulses in crankcase.
But if on loosening it blows out of your hands and hits the hood, you've got a problem.
If it just sits there and dances, you have a good engine and a bad sealing cap.

Originally Posted by KLXD

A bleed wouldn't work.
Unlike a gas engine where the PCV outlet is plumbed downstream of the throttle plate,
there is virtually no vacuum in the TDI intake system unless the filter badly plugged.

Thanks "Ski in NC" & "KLXD",
KLXD - I agree about the vacuum... on these turbo models,
the "boost" also makes sure that any small low-pressure (a vacuum)
would be destroyed by the air being pushed down the throat of the engine by that turbocharger!
Ski in NC - I really like your Redneck blowby flow test!!
On our MB diesels we pinch off the breather air hose running from the valve cover and see
how long it takes for the engine to stalls!
I hope you are not the inventor of the "Redneck Intake Manifold Flame-throwing Cleaner" method...
for I would NOT be so brazen as to get aluminum that hot and then quince it with cold water!
I cooked my on the patio inside a smoker Bar-B-Q and then let it cool off very slowly before I then
pressure washed the interior surfaces with 1,500 psi water-spray!
Regards,
Sam

[jake8842]

Are you sure the egr valve is not leaking?? I would be willing to bet it is.
Sprays out the vent hole on the front and looks like the oil filler cap is leaking. Repair = replace egr valve

[Bran Diezel]

i asked a guru at the dealership and he told me to just flip the rubber gasket under the cap over.

i did it and for the most part i'm staying alot cleaner. i think my egr has a smidge of a leak though.

[MrSafety]

Originally Posted by jake8842

Are you sure the egr valve is not leaking??
I would be willing to bet it is.
Sprays out the vent hole on the front and looks like the oil filler cap is leaking. Repair = replace egr valve

Originally Posted by Bran Diezel

i asked a guru at the dealership and he told me to just flip the rubber gasket under the cap over.
I did it and for the most part i'm staying alot cleaner. i think my egr has a smidge of a leak though.

"jake8842" - I will double check this next week when I get my hands on the car...
but I'm inclined to say not so because this last winter I did the intake cleaning and at that time I replaced all gaskets/seals on the EGR!
"Bran Diezel" - I have three times now replaced the oil cap with a different one and the last time was a new OE cap.
I'm going to throw two new flat gaskets on the oil cap... p/n = 06A-103-483-D ...
and see how they fit or if this makes removal of the cap overly difficult!
IF it is too difficult to turn, then I'll look for a sheet neoprene material that just a bit thicker than the OE gaskets and try making my own!
Thanks,
Sam Ross

[KLXD]

The EGR seal he refers to is internal on the shaft and not replaceable.

[Bran Diezel]

i was talking about the big ass rubber o-ring between the cap and valve cover

[golf.angers]

i have the same problem and i changed the cap at its still doing it i don't know what it is its not leaking from my egr clearly the cap. could it be that my ccv is blocked ?

[josh8loop]

Originally Posted by golf.angers

i have the same problem and i changed the cap at its still doing it i don't know what it is its not leaking from my egr clearly the cap. could it be that my ccv is blocked ?

You could check your CCV oil demisting pads like I did in this video:

http://www.youtube.com/watch?v=kEZzSUQONVA


They may or may not be gunked up. Mine were pretty clean, but I've heard guys say theirs were pretty dirty.





..

[T_D_I_POWER]

Double the no. of gaskets and it should stop oil from leaking/seeping OFC

2 gaskets on OFC


Double gaskets shown slightly protruding the OFC flange. Smear oil on the gasket for easy removal.


Peace of mind

[MrSafety]

Originally Posted by jake8842

Are you sure the EGR valve is not leaking??
I would be willing to bet it is.
Sprays out the vent hole on the front and looks like the oil filler cap is leaking. Repair = replace egr valve

"Jake8842" & Others...
I think you are probably correct that the leak is coming from the EGR (or at least from that direction)!
After installing a new "Breather Filter/PUCK" on top of the valve cover,
to my surprise I found there was noticeably less of a sign of the oil leak at/near the Oil-Filler Cap... BUT...
then yesterday I wrapped a medium square of aluminum foil over/around the Oil-Fill Cap...
and this a.m. when I checked the foil for new signs of a leak,
well I found none on the inside and a small, fain oil spot on the outside of the foil...
and so positioned that it came either directly from the "weep-hole" on the front side of the vacuum actuated "engine-kill flapper valve"...
NO... now I think it is from below the main EGR valve's diaphragm... possibly from its butterfly vavle shaft's hole!?
Q1 - IF leaking from one of the front shaft holes, do you think I could:
..... (a) clean out the shaft opening thoroughly,
..... (b) put in a little packing... then
..... (c) fill it with some of that supper metalized epoxy stuff!?... OR
Q2 Maybe it is blowing out of a leak in the turbo-pressurized air supply tube
at/near where it's rubber flex-coupling that connects to the EGR's flange!??
So I think you are right " Jake8842 " and I'm one step closer to solving this mystery as well as FIXing the problem.
So I guess I'm back to wrapping either more aluminum foil around and squeezing it tightly around these new suspected areas...
or maybe paper towels and use some narrow painter's tape to hold it in place until the oil spot first shows through!?
Tomorrow I'm changing both lower-control-arms and lower ball joints...
and this will give us a chance to examine things closely and IF we do NOT find an obvious leak,
then apply either the foil or paper towels!?
Sam Ross