Product description

Every fuel tank needs venting; it is a closed system, so to speak. If this were not present, an underpressure (vacuum) is created that affects the fuel supply and could even lead to implosion of the tank. For the above reasons, every tank is equipped with a vent, so that the released space is immediately filled with air (so that underpressure cannot occur). Usually this vent is located in the tank cap and is constructed so that air can be drawn in, but no fuel can come out.

To ensure proper venting of the tank, it is fitted with vent connections at the places where air bubbles may form that remove the negative or positive pressure through the filler neck or an expansion tank. Overpressure is caused by expansion of the fuel. Depending on how the fuel tank is constructed, this excess pressure can only be removed via vent hoses or an expansion tank must be involved. On the Bus T25, two expansion vessels are used to store the excess pressure, which are connected to the tank by hoses.

When installing a new vent or overpressure hose, it is advisable to also replace the rubber mounting grommets with it. In many cases, these have hardened, so a proper seal can no longer be guaranteed. If you squeeze the grommet and hairline cracks appear, you can assume that the grommet has dried out and needs to be replaced. Listed below are not only the hoses, but also any connection parts (which are not always included).

until 1983 (chassis no. 24-E-000 213)
3975 : hose between filler neck and breather pipe
70497 : mounting grommet breather pipe in tank
70497 : until 1980 (chassis no. 24-A-059-000) mounting grommet breather pipe in filler neck
70499 : expansion tube between left and right part of the tank incl. connections and grommets
70497 : loose mounting grommets for above pipe
70498 : expansion tank float valve grommets
980 : hose Ø 5 mm applied on the various connections from tank to expansion tank and pipes
981 : hose Ø 8 mm between expansion tank control valve and end piece left and right

from 1983 (chassis no. 24-E-000 214) and later
70500 : breather pipe filler neck to tank including connection
21268 : mounting sleeve breather pipe on filler neck from chassis no. 24-D-114 613 and later
70497 : mounting grommet breather pipe in tank
70499 : expansion pipe between left and right part of tank incl. connections and grommets
70497 : loose mounting grommets for the expansion pipe
70498 : expansion tank float valve grommets
980 : Ø 5 mm hose applied on several connections from tank to expansion tank and pipes
981 : Ø 8 mm hose between expansion tank control valve and end piece left and right

Fuel tanks
If you are looking for a new fuel tank for your T25 Bus please follow the reference below:
70492 : till July 1985 (no injection) with filling aperture of 69 mm
70493 : from August 1985 and later (no injection) with filling aperture of 48 mm
70494 : all construction years with injection with filling aperture of 48 mm