In the workshop, we’re currently seeing a trend that’s causing us - and especially your transmissions - quite a headache. In recent months, there’s been a growing number of cases where the seals on the pressure sensors (between the control unit and the hydraulic assembly) have been literally “drowned” in brake cylinder grease or similar assembly compounds.
We get the idea: you want the seal to slide on smoothly and fit snugly. But be careful: this is an absolute no-go!
The problem: Chemical incompatibility
Brake cylinder grease is designed for brake fluid (DOT), not for the chemical composition of DSG oils. When this paste comes into contact with the transmission fluid, the substances simply do not mix.
The result? The paste changes its consistency and can clump. It can be flushed into the hydraulic system or the pressure sensors of the control units, or - even worse - attack the chemical structure of the sealing rings. You can clearly see what the whole thing looks like after a very short time in the featured image. This not only compromises the seal, but simply has no place in a sensitive component like the 0B5 mechatronics system.
The solution: Less is more
It’s actually quite simple and saves you time and money:
- No grease.
- No assembly paste.
- Just fresh gear oil.
Lightly coat the O-rings with the oil that goes into the gearbox anyway, carefully insert the sensors, and you’re done. That’s all it takes for a durable and secure seal.
Do your mechatronics a favor and stick with oil!