@Michael II: Larger membrane tank for older VTG loaders?

Hi everyone,

"Recently, I've been experiencing frequent problems with my variable geometry turbocharger (VGT). It seems that carbon buildup is causing the vanes to stick at the bottom position. As a result, the small diaphragm actuator (97 AFN model - the actuator is only about as thick as the pressure lines behind the turbocharger) is unable to move the vanes to other positions (needed for high boost pressure)."
Even repeatedly adjusting the VTG (Variable Turbine Geometry) using the recheck generator at the solenoid valve during operation only provides temporary relief.

In my wife's 2001 ALH-Ibiza, there's a significantly larger diaphragm pump (roughly the size of the intake manifold between the mass airflow sensor and the turbocharger), which presumably generates more force to move stuck mechanisms.

My question: Are there larger sizes available as spare parts, and can they be mounted as a replacement for the smaller size without any modifications to the holder or threaded rod?

Hello Ulf,

Unfortunately, the membrane dosing unit is not available for purchase as a single replacement part.

Quote:

Unfortunately, the membrane diaphragm is not available for purchase as a single replacement part.

Hi Michael,

. . . it would have been too easy.

Well, I'll keep trying. If the occasional lack of boost pressure wasn't so annoying, one could almost consider experimenting with troubleshooting strategies to be enjoyable.

But these experiences make me imagine how helpless one might feel without a boost pressure gauge - when the engine sometimes starts like an SDI and you can only guess what might be the cause of it.
Then, keeping in mind the "expertise" of some workshops, which manifests itself more in billing than in troubleshooting... good night, VAG-Land!

Hello!

Car: Volkswagen Golf 3 TDI AFN.
'I'm planning to take my car to the service department soon, and I've noticed that the acceleration has been feeling a bit like an SDI lately. What specific issues should I bring to their attention?'
As you already mentioned, they apparently check something (but without finding the error), and then the bill is all that remains.

Other symptoms include a 'wave-like' acceleration, and you can clearly feel that it loses power in the upper RPM range and doesn't pull through.
It was once said that the turbocharger pressure was too high, but they never came up with any ideas to address it... (or they couldn't).

Best regards, D.

The manufacturer is fully aware of the problem with the pressure vessel being too small. Ultimately, the size has been changed throughout the entire series.
Best regards, Lanz.

yomam wrote:

Since I'm going to the service department soon, and I've actually noticed that the "acceleration" has been feeling a bit like an SDI lately, what should I bring to their attention?

Hi.
basically, due to a likely stiff or "sticky" VTG (Variable Transmission Gear) mechanism.
I'm checking it using a 60 ml syringe and a short piece of tubing that I attach to the charging port. When drawing the fluid, the VTG rod should move approximately 1 cm, feeling "soft" (not stiff), depending on the position of the syringe.
It often gets stuck at the bottom stop and only releases (sometimes) with a jerk, after I've already drawn up the entire dose.

But a professional workshop probably wouldn't resort to such testing methods – a doctor's syringe, pah, how trivial. We have our own 1551.

Quote:

Other symptoms include a "wave-like" acceleration, and you can clearly feel how it loses power at the top end and doesn't pull through. It was once said that the boost pressure was too high, but they never came up with the idea to do something about it... (or they couldn't)

Theoretically, the problem could be caused by the solenoid valve, the hoses, or the VTG itself. Unfortunately, it's probably the latter, as a "thorough" repair likely involves a costly charger overhaul or replacement.

As I mentioned, you can somewhat mitigate the effects with electronics that control the valve in a 1 Hz cycle, causing the VTG to constantly oscillate between its extremes (assuming it's still functional).
In any case, I recommend installing a battery voltage indicator so that you can at least check it when the vehicle is acting up again.

Lanz wrote:

The manufacturer is fully aware of the problem with the pressure vessel being too small. Ultimately, the size has been changed throughout the entire series. Best regards, Lanz

Hi Lanz

Do you happen to know from which year of production the larger sizes are available?
If I ever decide to get a "cheap fix" by salvaging parts from a scrapped vehicle, here's what I'd be looking for over the phone. Knowing the relevant production years in advance can be helpful.

No, Ulf, not exactly, but certainly for the past 2 years.
Best regards, Lanz

Hello Yomam!

Hi!

Your symptoms sound more like a faulty mass airflow sensor (MAF), try replacing it with a different one.

Best regards,
Uwe