Working on a 1997 Jetta that has become a problem child. It first came to us several months ago after going through 4 other shops that couldn't put it right. The major issue at that time was that it barely ran. The owner had been told it needed a new engine. We checked timing and discovered it was way, way off (cycling between 255 and 36, and would barely stay running when in basic settings). Took a while to figure out how to make it come into range, but finally got it timed right and it seemed to run fine. As part of the diagnosis of that issue, to ensure that the engine was OK, we did a compression test and the motor seemed perfectly fine -- 400+ in all four holes.
Now that it runs OK and the owner has been able to start driving it regularly, another problem has surfaced that is hard to figure. The car smokes and uses oil. However, blowby is zero, and when I say zero, I mean literally nothing coming out of the cap. Compared it to another known good TDI with low miles, and the other one had a fair amount coming out of the oil fill hole when running -- as every TDI I have ever worked on has. This AHU, though, has nothing. If you put your hand over the fill cap when running, it seems to alternate between very slight pressure and slight *vacuum*. This is with the port from the CCV to the intake plugged off, of course, so there is no other outlet for the blowby that I can think of, other than out of the oil fill...? So I am having to conclude that it is going someplace I am not aware of, and perhaps even being drawn there by vacuum, since otherwise I cannot see how there could ever possibly be negative crankcase pressure, except in an instance of extreme air filter restriction and an open CCV.
Trying to figure out what is going on here. There is no vacuum source anywhere in the car except for the vacuum pump. Can the pump fail in such a way as to suck on the crankcase side? All diesels in my experience have a fair amount of blowby even when in perfect condition. This car should have at least some. Where is it going??
Any thoughts on this, anybody seen anything similar? I work on these cars every day and have never seen one do something like this... beating my head against the wall.
Still starts and runs fine, aside from a big cloud at startup, a constant haze while idling, and big puffs when on the pedal; and gives every indication of having plenty of compression. Timing and all other basic factors are spot on. Appreciate any input.
Now that it runs OK and the owner has been able to start driving it regularly, another problem has surfaced that is hard to figure. The car smokes and uses oil. However, blowby is zero, and when I say zero, I mean literally nothing coming out of the cap. Compared it to another known good TDI with low miles, and the other one had a fair amount coming out of the oil fill hole when running -- as every TDI I have ever worked on has. This AHU, though, has nothing. If you put your hand over the fill cap when running, it seems to alternate between very slight pressure and slight *vacuum*. This is with the port from the CCV to the intake plugged off, of course, so there is no other outlet for the blowby that I can think of, other than out of the oil fill...? So I am having to conclude that it is going someplace I am not aware of, and perhaps even being drawn there by vacuum, since otherwise I cannot see how there could ever possibly be negative crankcase pressure, except in an instance of extreme air filter restriction and an open CCV.
Trying to figure out what is going on here. There is no vacuum source anywhere in the car except for the vacuum pump. Can the pump fail in such a way as to suck on the crankcase side? All diesels in my experience have a fair amount of blowby even when in perfect condition. This car should have at least some. Where is it going??
Any thoughts on this, anybody seen anything similar? I work on these cars every day and have never seen one do something like this... beating my head against the wall.
Still starts and runs fine, aside from a big cloud at startup, a constant haze while idling, and big puffs when on the pedal; and gives every indication of having plenty of compression. Timing and all other basic factors are spot on. Appreciate any input.
