Hoses, Tanks & Sensors

Somewhere it evaporates or somewhere internal. A hairline crack in a plastic pipe or an expansion tank seam weeps only under pressure at temperature, and the escaping coolant dries on hot components leaving a crusty deposit rather than a pool. A failing cap does the same by releasing pressure early. Internally, a head gasket or an exhaust gas recirculation cooler can pass coolant with no external sign. A pressure test with the engine cold finds the external ones in minutes.

Read the number moulded into the pipe itself, which is how the factory catalogues them. Modern vehicles carry many separate sections across several circuits, and descriptions alone will not distinguish them, which is why the listings use numbers. If the moulding is unreadable, a dealer can identify the section from your vehicle identification number and the location, or you can send photographs and the routing through the quote form to have it checked against the catalogue.

For a simple rubber section between two spigots on an older vehicle, sometimes. For the moulded pipes that dominate current vehicles, no: they are formed to a specific three dimensional route, carry integrated quick connectors and sensors, and clear moving and hot components by designed margins. Generic hose bent to a similar shape kinks, chafes and fails, usually at the least convenient moment. The formed part is the reason this category exists as a numbered series.

Because it spends its life being pressurised and depressurised while hot, and the plastic embrittles with heat and ultraviolet exposure over years. Cracks appear along moulding seams and around the neck, often only weeping when hot and pressurised, which is why they can be missed on a cold inspection. Replace the tank rather than sealing it, since a repair on a pressure vessel is temporary at best, and fit a new cap at the same time.

More than most people expect. The cap holds the system at a rated pressure, which raises the boiling point of the coolant well above what it would be at atmospheric pressure, and a cap that releases early lets the coolant boil at a temperature the engine reaches routinely. That produces coolant loss, steam and overheating with everything else in good condition. Caps are rated, so fit the correct one rather than any that screws on, and replace it whenever the tank is replaced.

Clips, O rings and sensors sit right at the bottom of the range. Individual coolant pipes are modest. Expansion tanks and long moulded sections cost the most in this category, though all of it remains inexpensive against the damage that overheating causes. The live minimum and maximum are shown in the band at the top of this page. Because a pressure test identifies the exact section, testing before ordering avoids buying pipes that were never leaking.

Usually, and the difficulty is access rather than technique. Drain to below the section, release the clips or quick connectors with the correct tool rather than levering, fit the new pipe with fresh clips and O rings, refill with the specified coolant and run the bleed procedure. Quick connectors need care, since a damaged shoulder leaks the moment the system pressurises. Work on a cold engine, because hot coolant under pressure causes serious burns.

Because trapped air stops flow rather than merely reducing it, and it collects at the highest point of a circuit, which is frequently where flow matters most. The symptoms are overheating, weak cabin heat and thermal faults, all of which look like a failed component and none of which are. Many vehicles specify a routine that runs pumps and cycles valves through a scan tool. Follow it and retest before concluding that anything further has failed.

Only the grade named for your vehicle. This category is where the consequences of getting it wrong show up first, because precipitated additives settle in the narrowest sections: the quick connectors, the small bore pipes and the sensor ports. A level sensor coated in deposit reads badly, and a partially blocked pipe starves whatever sits downstream. Buy a sealed container of the specified product, dilute to the stated strength if it comes as concentrate, and if you are replacing pipes anyway, take the opportunity to flush and refill rather than reusing what came out.

Only where the numbered section agrees. Routing follows the packaging of the specific vehicle and drivetrain, connector types differ, and lengths change with engine and pack variants that share a body. A pipe that is nearly right will sit under tension or foul something hot, and it will fail there. Read the number from your existing pipe, match it, and where the reference brings back nothing, send it through the quote form with photographs of the routing.

At the manufacturer's interval, which on current long life products is measured in years rather than a short mileage, and sooner if the coolant looks discoloured, contains debris or has been topped up with something unknown. The inhibitors deplete over time whether the vehicle is used or not, and once they are gone corrosion starts inside components you cannot see. A coolant change is inexpensive insurance on a system whose components are not.

Yes. Moulded coolant pipes are shaped around the engine bay they belong to, so there are many of them and each sells slowly, which is why a number of these references wait for an enquiry. Give the reference and the reply comes back against that shape. Where the pipe you need is one of a pair sharing a quick connector, ask for both. Connectors are the usual failure point on an ageing circuit and they rarely come apart intact. Add a new pressure cap while you are at it, since a cap that no longer holds pressure lets the system boil at normal temperature.