Blow by 2001 alh

Nate660

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Feb 22, 2017
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2000 Jetta 331k
Engine I have had blowby how much is acceptable? The oil cap bounces around but doesn't blow it off. From my understanding these engines will have blowby?
 

oilhammer

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outside St Louis, MO
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There are just too many to list....
All engines have blowby. Are you having some problem that is prompting you to look for something that likely is not a problem?
 

Nate660

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Feb 22, 2017
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Kansas
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2000 Jetta 331k
Nope good fuel mileage running fine. Just noticed it the other day while looking over the engine bay with it running. I just want to know how much is ok because I travel quiet frequently and don't want to be left sitting do to low compression
 

UhOh

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If the oil cap doesn't seal well get a new one: they're cheap.

If you're worried about the engine's compression get a compression test done. Face your fears head-on!;)
 

oilhammer

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outside St Louis, MO
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There are just too many to list....
It sounds like there is nothing wrong with your engine. I'd not give it a second thought. If it runs good, no excessive smoke or strange noises or hard starting, no bad oil consumption, then motor on.
 

Nate660

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2000 Jetta 331k
No oil consumption at all I'm at 4k miles and it's still full on the stick. Wide open throttle no smoke just alittle black at first which is normal with my karma tune. Love this little motor to death. I have a lifted 2006 mega cab cummins and it just sits because I like this car to much lol
 

Powder Hound

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The engine will seem as though there is excessive blow by, but this is more a result of the high compression than anything else. Some people think it has to do with the vacuum pump exhausting into the valve cover plenum, but the volume from that pump is negligible.

What is the mileage doing? If it drives well, isn't smoking, gets proper mileage, then no worries.

Excessive blow by would result in oil leaking like crazy from blown out seals because the CCV would not be able to handle the volume of gasses.

Seriously, you have no worries.

Drive on!

Cheers,

PH
 

AndyBees

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Silver 2003 Jetta TDI, Silver 2000 Jetta TDI (sold), '84 Vanagon with '02 ALH engine
Take the advice of Oilhammer and Powder Hound ......

Problematic blow-by with high miles was a thingy with the 1.6 VW engines (and 1.5). I took the assumption that as long as it had oil in it and would start, no worries.
 

jimbote

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spiral arm, milky way (aka central NC)
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Tacoma 4x4 converted to TDI
vacuum pump exhaust ... if you need convincing run the engine with the vacuum pump nipple sealed off, then with it fully open ... the amount of volume that little pump puts out is far from negligible but quite astounding
 
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compu_85

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La Conner, WA
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... None :S
Ya that's a good point about the vacuum pump emptying into the head.

The general rule is that if the blowby just makes the loose cap dance around it's fine. If the cap is blown off the valve cover, there's too much.

-J
 

KLXD

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'98, '2 Jettas
There should be no flow from the vacuum pump unless you have a vacuum leak. It is capable of pumping a lot of volume but it shouldn't be doing it.

Except when it is called on to actuate something like the TC. Then there will be a momentary flow.
 

oilhammer

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outside St Louis, MO
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There are just too many to list....
There should be no flow from the vacuum pump unless you have a vacuum leak. It is capable of pumping a lot of volume but it shouldn't be doing it.

Except when it is called on to actuate something like the TC. Then there will be a momentary flow.
Really? Isn't the N75 and N18 "open" from the source (vacuum pump) side to the exhaust (air cleaner) side during much of its normal operation? The EGR and VNT are not self-venting, so that vacuum needs to go somewhere, which means if it is constantly venting some vacuum, then it has to constantly be producing some vacuum, and that is going to be pushed into the crankcase. Obviously, this is a very small amount (volume) and the engine is designed to accommodate this. Essentially a tiny bit of filtered air (air cleaner post filter) being pushed into the crankcase in some manner most of the time, and being "lost" in the normal crankcase pressure scavenging that occurs as the inlet air is pulled past the PCV right where the heater sits.

At least, that is what I remember from school. If the N75 was just allowing all the vacuum it has available all the time then the actuator would just stay pulled down all the time the engine is running. Same for the EGR solenoid.
 

AndyBees

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FWIW, I have a Vacuum Gauge on the "vacuum system" on my ALH in the Vanagon. When the engine is running, it holds about 23 inches (depending on elevation). The amount doesn't change when I accelerate. I assume the pump is strong enough to keep the vacuum about the same at all times, with one exception. When I hit the brake pedal, the vacuum gauge will dip down and recover almost immediately.

Interestingly, when I shut-down the engine, vacuum drops almost immediately. So, either I have a leak somewhere or the check valve doesn't operate properly. I do have a reserve tank and an individual filter for the system.
 

Nate660

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Feb 22, 2017
Location
Kansas
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2000 Jetta 331k
Well can someone post a video of an engine that they think is healthy so I can get an idea of what I have. Or I guess I could post a video of my engine also
 

KLXD

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Aug 22, 2009
Location
Lompoc, CA
TDI
'98, '2 Jettas
Really? Isn't the N75 and N18 "open" from the source (vacuum pump) side to the exhaust (air cleaner) side during much of its normal operation? The EGR and VNT are not self-venting, so that vacuum needs to go somewhere, which means if it is constantly venting some vacuum, then it has to constantly be producing some vacuum, and that is going to be pushed into the crankcase. Obviously, this is a very small amount (volume) and the engine is designed to accommodate this. Essentially a tiny bit of filtered air (air cleaner post filter) being pushed into the crankcase in some manner most of the time, and being "lost" in the normal crankcase pressure scavenging that occurs as the inlet air is pulled past the PCV right where the heater sits.

At least, that is what I remember from school. If the N75 was just allowing all the vacuum it has available all the time then the actuator would just stay pulled down all the time the engine is running. Same for the EGR solenoid.
Maybe I'm mistaken but I thought the common port on the valves went to the actuators, the NC port to the pump and the NO port to the air cleaner so the pump would only suck on the actuator when the valve was energized. When it deenergized the make up air is applied to the actuator from the air cleaner.

I think it has to be thus. If it were plumbed as you say with the pump going to the common port, when the valve deenergized the actuator would be locked up. No make up air.

Are not N75 and N18 pulsed for partial actuation of the TC and EGR valve?

After further thought there would be some flow at idle but only while the EGR is being controlled. The TC is out of the picher but during the time the EGR valve is open at idle N18 would be modulating the EGR position so there would be some small flow as N18 opens and closes.

Unless the EGR is either completely open or closed. I dunno but I thought it was modulated.
 
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jimbote

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spiral arm, milky way (aka central NC)
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One other thing is that the pistons sweep the same volume going down as they do going up. So the will move some air around.
very little ... how i know this is my buddy Tom did a vacuum pump delete on his ALH to fit it into a bay window bus ... basically it had ZERO crankase pressure, nada .... same motor running previously with a vac pump had tons of what everyone is wrongly calling blowby... real blowby is smoky... a healthy ALH with vac pump chimneys clean air that is almost 100% vacuum pump exhaust
 

oilhammer

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outside St Louis, MO
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There are just too many to list....
Maybe I'm mistaken but I thought the common port on the valves went to the actuators, the NC port to the pump and the NO port to the air cleaner so the pump would only suck on the actuator when the valve was energized. When it deenergized the make up air is applied to the actuator from the air cleaner.

I think it has to be thus. If it were plumbed as you say with the pump going to the common port, when the valve deenergized the actuator would be locked up. No make up air.

Are not N75 and N18 pulsed for partial actuation of the TC and EGR valve?

After further thought there would be some flow at idle but only while the EGR is being controlled. The TC is out of the picher but during the time the EGR valve is open at idle N18 would be modulating the EGR position so there would be some small flow as N18 opens and closes.

Unless the EGR is either completely open or closed. I dunno but I thought it was modulated.
Easy to test. Put a vacuum gauge on the vent line to the air cleaner. :) You'll see it has some vacuum all the time. Hence the constant, albeit small amount much of the time, flow of clean filtered air through the vacuum pump into the crankcase, and out the breather.
 
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