Hose and flexible for MAN / Mercedes trucks and buses

Hoses and flexible connectors absorb movement, vibration and thermal expansion, but their construction varies by application. Coolant hoses, fuel hoses, compressed-air hoses, hydraulic hoses and exhaust flex pipes are not interchangeable. When selecting a part, check its inner diameter, wall thickness, length, bend radius, connection type, working pressure, temperature range and material compatibility. EPDM (ethylene propylene diene monomer), for example, is used in coolant systems; fuel and hydraulic lines require materials and reinforcement approved for the relevant fluid and system pressure. An exhaust flex pipe, by contrast, needs a heat-resistant metal bellows and the correct connection diameters.

Even within a single model range, hose routing can vary according to the engine, emissions specification and vehicle body. A coolant hose for a MAN TGS with a D26 engine may not fit a version with a D20 engine; the same applies to Mercedes Actros variants with an OM 470 or OM 471 engine. On trucks, buses and vans, factors such as wheelbase and auxiliary equipment also affect the available space. Always identify parts using the chassis number. A visual comparison or selection based solely on the model name is never sufficient.

Typical symptoms include coolant loss, a drop in compressed-air system pressure, a fuel smell, a hydraulic leak, or exhaust noise and soot deposits around a flex pipe. Hardening, cracks, swelling, abrasion and traces of oil or coolant provide clues, but do not always reveal where a leak starts. First, clean the connections and trace the hose routing. Then inspect the entire length of the hose, including areas behind clamps, at pass-through points and near hot components.

Next, carry out targeted tests. Pressure-test the cooling system in accordance with the vehicle specification and inspect the connections under pressure. Check the compressed-air system using a suitable leak-detection method, and compare pressure build-up and pressure retention with the specified values; take the EBS (Electronic Braking System) configuration into account. Inspect hydraulic hoses only after the system has been safely depressurised. If an exhaust flex pipe is suspected of being faulty, soot deposits and a leak check with the engine running can help locate the cause. At the same time, check whether faulty engine or exhaust mounts are placing excessive strain on the flexible connection.

Before fitting the new part, check it against the specified connections, pressure and temperature ratings, and required free length. A hose that is too short pulls on its connections; a bend with too much slack can kink or rub against a moving component. Fit hose clamps in the specified positions and use only suitable couplings and seals for hydraulic connections. Also replace damaged supports or heat shields if they caused the original fault.

After installation, check the routing as the engine moves and, where applicable, while tilting the cab. Fill and bleed the relevant system according to the vehicle procedure, repeat the leak or pressure test, and check for seepage and signs of contact after a test drive. This addresses not only the leak, but also the strain that causes a hose or flexible connector to fail prematurely.