Modular coolant hoses: typical failures and best maintenance practices


As car engines have become more complicated, so have their hoses. Today, modular coolant hoses with built-in components have become the norm, containing plastic connectors, such as quick connectors, T- and Y-shaped branches. While they make for lighter cars, hence less CO2 emissions, they also fail earlier and more frequently, due to the plastic connections becoming brittle. In this article, we zoom in on 1.6 diesel engines (fitted to popular vehicles such as the Citroen: C3, C4, C5, Berlingo, Jumpy; Peugeot: 206, 207, 307, 308, 407, Expert, Partner; and Ford: C-MAX/Fiesta/Fusion) to explain what can go wrong when removing a modular coolant hose for routine maintenance. Read on to find out why a new Gates modular hose assembly should be installed whenever you install a Gates PowerGrip® Kit!

Modular hoses for complex cooling systems

We’ve come a long way since the traditional rubber-shaped hoses of the eighties and nineties, and even from those of 2000 onwards, which already had one or two branches. These days, with hybrids and electric vehicles taking the market by storm, cars are outfitted with various modular hose assemblies. Their built-in components control the coolant flow to supplementary areas such as turbochargers and battery packs. 

modular coolant hoses


Modular cooling hose evolution


In addition to making engines (and hoses) more complex, OEM vehicle manufacturers have been reducing the weight of vehicle system components for many years in order to increase fuel efficiency and reduce CO2 emissions. Turning to plastic moulded hoses, housings and joint connections within the coolant system, manufacturers not only managed to make their vehicle systems lighter; they also sped up the installation process. Quick connectors, for instance, click right into place nowadays, reducing the need for hose clamps and extra tooling on the production line. 

Why modern hoses fail earlier and more frequently

It’s not all good news, though. While old-style curved hoses needed replacing after ten to fifteen years, the life span of modular coolant hoses has shortened to eight to twelve years (with failures occurring typically between 90,000 and 150,000 kilometres or 60,000 to 95,000 miles). The culprits? Engine vibrations and increased under-bonnet temperatures.

As with traditional curved hoses, high temperature and prolonged exposure to fluids cause the rubber of the modular hose to become soft, expand and lead to hose failures. Plastic connectors, in turn, become brittle and susceptible to breaking due to engine vibration and the stresses of circulating coolant. Finally, quick connectors can fail when hoses are removed for general cooling system maintenance.

What does this mean for maintenance?

During scheduled servicing intervals such as timing belt system renewal, quick connectors usually have to be removed to aid draining and flushing of the vehicle’s cooling system. During the removal or installation process, the brittle plastic of the quick connectors, as well as of the T and Y connectors, can fracture, causing leakage within the coolant system. Changing the coolant at correct service intervals may help reduce early life failures (ELF), but that’s not the only precaution you have to take.

Gates recommends carrying out a thorough check of the modular coolant hose and plastic connectors for signs of damage when removing and installing a timing belt system and water pump to (PSA) 1.6 diesel engines. After all, due to the location of the plastic connectors of the modular hose in relation to the water pump, removal and installation procedures require handling of both the water pump and the modular hose assembly, which can lead to fracture damage occurring around the plastic connectors.

Our advice would be to install a new Gates modular hose assembly 02-1730 whenever you install Gates PowerGrip® Kits KP15598XS, KP15656XS, KP15688XS, KP25598XS to vehicle applications containing Gates water pump WP0055, Gates modular hose assembly 02-1730 or their original Citroen, Peugeot or Ford equivalents 1201.G9 and 1336.X3, 1230674, 13464681.



modular coolant hoses


Gates hose 02-1730


modular coolant hoses


Gates water pump WP0055