Whats an acceptable amount of blow-by

77machomopar

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1999.5 Jetta TDI 5 speed
I jsut recently replaced my turbo due to oil leaking by seals. And now this one is doing the same thing. It is a used trubo with 60k miles of it. it wasnt leaking at all when i put it on and then about 250 miles later it started to.

While the car is running if i loosen the oil fill cap off the blow-by will shoot the cap off of the valve cover. Whats an acceptable blow by level. thanks
 

Ski in NC

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Wilmington, NC USA
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2001 Jetta ALH 5sp stock
Four cylinder four strokes normally have pressure pulses in the crankcase that cause cap to "dance" when loosened, and cause oil mist to come out when cap is off. That's normal. Hard to tell if blowby is high by just removing the cap.

Could be high blowby from rings, but could also be something clogged in the crankcase vent path. Take hose off from ccv hockey puck on cam cover and see what kind of flow you get out of that. Might also pull cam cover and see if vent path and mist separator is all clogged up with gunk. Could be a restriction in the puck. I have no idea what is actually in the puck.

High flow out of puck hose, high blowby from rings.

Puck flow path clogged, normal blowby flow getting restricted.
 

77machomopar

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1999.5 Jetta TDI 5 speed
3 days ago i cleaned out my intercooler from when the first turbo leaked oil. i got about 1qt out of it. Toped off the oil in the engine and drove it 3 days. the oil went down about 1/8 inch on the dipstick. i checked it in the garage on a level surface with the engine at ambiant temperature. I am going to pull the intercooler again and check for more oil from the current turbo to see if its blown too.

I am getting plenty of air flow through the ccv puck. So i am thinking that the piston rings are shot and is causing this loss of oil. It smokes a little bit at an idle and at wide open throttle.
 

jollyGreenGiant

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MA
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03 Golf TDI GLS ( my 5th TDI ), 03 Eurovan GLS - VR6 :(
If you have a vacuum leak, your vacuum pump will be pumping into the crankcase at a high volume and show lots of output through the cap, plug up the vacuum pump outlet and see what happens to blow by, a lot of cars move oil into the intake cause of this too...
 

77machomopar

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1999.5 Jetta TDI 5 speed
Diesels have blowby.

Not enough blowby to blow the oil fill cap against the hood when its just sitting on the valve cover. my 5.9litre cummins diesel with 330,000 miles dont have even a quarter of the blow by as this tiny 1.9litre.
 

85_305

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Buffalo NY/FT Bragg, NC
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1999.5 Jetta 5spd
This is true this is true........

These motors do have a good bit of blowby stock.. but I dont believe they'd have enough to throw the oil cap?

Try taking the dipstick out of the tube, and put your finger over the opening. Report back what happens.
 

77machomopar

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i just feel pressure against my thumb. the ccv puck is not clogged. blow by amounts dont change by a warm or cold engine
 

85_305

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I'm pretty sure that's bad if you can feel it pulsiong in the oil dipstick tube. Sounds like you have an issue with the vac pump or something... I dunno man but I don't think that's normal
 

turbocharged798

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Ellenville, NY
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99.5 black ALH Jetta;09 Gasser Jetta
Not enough blowby to blow the oil fill cap against the hood when its just sitting on the valve cover. my 5.9litre cummins diesel with 330,000 miles dont have even a quarter of the blow by as this tiny 1.9litre.
Becuase it probably does not have the vacuum pump discharging into the head.

You might have a vacuum leak somewhere.
 

77machomopar

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1999.5 Jetta TDI 5 speed
i am going to check the vaccuum pump. i guess i can just plug the pump right at the vac outlet and see what pressure i get.

cummins engines have a gear driven vac pump that will pressurize a crank case like what my tdi is doing too. thanks ill try it out tommorrow and hope for the best.
 

FlyTDI Guy

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'01 Jetta GLS
i am going to check the vaccuum pump. i guess i can just plug the pump right at the vac outlet and see what pressure i get.

cummins engines have a gear driven vac pump that will pressurize a crank case like what my tdi is doing too. thanks ill try it out tommorrow and hope for the best.

Same for the TDI actually... the vac pump does discharge into the valve cover area. The ALH does have a lot of pressure in the valve cover, by my measure. I've worked w/gassers for years and, in comparison, my little TDI puts out the stuff. I was concerned initially but it is normal. I'm sure the vac pump output adds to it but I'm not certain how much.
 

77machomopar

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1999.5 Jetta TDI 5 speed
i started the car and took the vac pump hose off and blocked it with my thumb. the oil cap didnt jump off as far as it does with the vac pump hooked up. I am going to go to graingers and get silicone hose to replace the vac lines today.

The car still starts hard and always has a blue haze out of the exhaust and a huge cloud of blueish black smoke when i go to wide open throttle. thanks
 

Yblocker

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1997 Passat
Interesting. My 1Z has this "blowby" too- not smoky. My brakes work fine, but the pedal feels harder than those in the average power assisted gas engine car. I always thought it was the nature of the beast or maybe glazed pads, although the brakes are quiet. How is the vacuum system routed through the head?
 

77machomopar

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my brakes and vaccum operated parts all function properly too.

I was also thinking to the blue smoke and engine oil loss could it be valve stem seals?
 

77machomopar

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1999.5 Jetta TDI 5 speed
I was just thinking, I pulled the coolant temp switch off and the car started inmmediatly this mourning, and the engine was stone cold about 35-40 degrees F. Does this still sound like the ecm needs programming. My car is one of those 99.5 year models. It still puts out a cloud of blueish smoke.
 

77machomopar

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yea the glow plugs stayed on for 20 secs. started really easy. i tried cycling the gp's to see of the same thing would occur but it would still crank forever. sounds like its tuning time
 

77machomopar

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I was thinking about everything that i have been trying with fixing this car. i came to the conclusion that a tuned ecm might fix my long cold crank times. But everything i read says that the 99.5 only had hard hot start problems that are fixed by tuning.

i still have a steady cloud of blue smoke when i start it and when idling at cold engine temp. Do you guys think that a tune will fix the hard starts or start looking for other symptoms.
 

77machomopar

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i just got a compression tester and all my cylinders where between 475-500 psi. i also had found a air leak in the fuel line so i fixed that. But it still cranks for a long time before it starts and has constant blue smoke at an idle. Is worn out injectors a possiblity?
 

Ski in NC

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2001 Jetta ALH 5sp stock
Good compression. How's injection timing? A little late makes for tough starts and smoky idle.

And yes, injectors as they age can affect starts and smoke. Check timing first.
 

77machomopar

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1999.5 Jetta TDI 5 speed
injection timing is between the two upper lines. ithink its like 67? the graph says within spec but advanced
 
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