Auxiliary Heater Installation - Air in Diesel Line?

Hi!

This winter, I purchased and installed a Webasto TermoTop E. The fuel supply for the heater is connected via a T-piece that is installed in the engine's fuel line, located at the rear of the tank. The rigid plastic diesel line had to be cut, a T-piece inserted, and then secured with clamps (all according to the Webasto installation instructions for the Lupo Diesel/3L, which is also a common-rail diesel!). Unfortunately, the engine fuel line in common-rail diesels is not transparent, so I can't see if any air bubbles are entering. In contrast, with the heater fuel line, small air bubbles occasionally make their way through. There are no starting problems with either the engine or the heater. What would be the consequences for the common-rail injectors if air bubbles occasionally enter the fuel supply during operation? Would the lubrication be severely affected? Or are there other disadvantages (besides a possible loss of power)?

"By the way, I'm also curious about something: Why do some STH (Swirl Torque Hybrid) installation kits (e.g., Golf TDI) use a metal pipe for fuel supply combined with plastic pipes for hard-to-reach areas, while other installation kits (as mentioned above) use a completely plastic fuel line? The exhaust gas temperatures should be relatively similar in the 3L Lupo compared to the Golf..."



Thank you everyone...
pretzel
Polo 1.4 TDI PD

Hello,

1. The throttle bore in the tandem pump acts as a steam separator. The steam then flows directly into the fuel return line.

2. The bypass ensures that air is removed from the fuel system.

Great, thanks Michael II. That definitely makes things a lot easier for me. So, if I understand correctly, the PD (peritoneal dialysis) has a clear advantage over the VEP (very low efficiency peritoneal dialysis) in terms of air bubbles, right?

pretzel