Tower-style engine and radiator configuration

Inside the vehicle, the most striking feature at the rear is the engine tower. The tower height varies according to the engine type: horizontally mounted (OM 936h) or vertically mounted (OM 936/OM 470). In all engine variants, the radiator is placed above the engine. Accordingly, the radiator and the engine air inlet are well above the level of upwardly projected dirt and splashes.

Horizontally mounted engines are fitted with a vertical radiator, and vertical engines with a horizontal radiator, to save space. The cooling water surge tank is located on the roof on both cases, again to save space. However, the level gauge for the refill reservoir and filling connections are placed in the engine compartment, for greater ease of maintenance.

Optimum access, effective noise insulation

All components are also easily accessed from the inside, through separately opened maintenance flaps. Noise insulation is boosted with quadruple seals over the maintenance openings, plus a hollow chamber seal arrangement.

The engine tower features a completely new insulation concept, based on a sandwich configuration with dual panels and an inside insulation layer. The elements are adhesively bonded to each other. On the passenger compartment side, this insulation covering has a further plastic layer, which is both pleasant to the touch and easy to clean.

Further increase in corrosion protection and quality

The Mercedes-Benz Citaro has gained an excellent reputation over the years for its outstanding quality, based on meticulous workmanship and also the cataphoretic electrodipping (CET) paint finish. This “e-coat” provides highly effective corrosion protection for the frame structure. Implementation of Euro VI requirements has enabled the developers to further boost the quality of anti-corrosion protection.

For example, the roof panelling now consists of a continuous glass fibre-reinforced plastic (GRP) strip. The strip is supplied in the form of a roll, painted white and given a protective gel coat layer.

The new engines have a combination of clearcoat paint and a wax layer. Further enhancements have also been made in the application of the underfloor protection and the cavity protective coating. Structural design changes mean that deposits of dirt are no longer able to accumulate in the wheel arches of the Citaro. Another anti-corrosion measure is the use of adhesive rather than welded joints in the entrance supports. Even the hinges and locks are given an extra spot waxing coating.

Additional improvements have also been made to components such as the optionally fitted cassette ramp. The ramp housing is now watertight, which reliably prevents corrosion. Servicing procedures have been simplified by reducing the number of structural components and ensuring they are easily accessible. Sensors now operate over the entire length of the ramp, by means of step mats. The front edge is marked with a blinking LED strip.

A comprehensive corrosion test carried out on the new Citaro has successfully confirmed the effectiveness of all these anti-corrosion measures. The test consisted of a salt spray test plus exposure to the effects of heat and moisture, and a poor road and winter trial. The compressed test programme replicated use in tough conditions over a period of 15 years. The results provide ample confirmation of the long-term stamina of the Citaro.