Straight Hoses

Straight silicone hose is sold by length, ready to cut for coolant, breather, vacuum and intake runs that need a plain section. Most come in 1 m lengths, from 5 mm up to 127 mm bore. Petrol- and oil-resistant versions, small hose kits with clamps, vehicle-specific intake hoses and plastic air intake parts are listed too.

Silicone stays flexible at temperatures that harden ordinary rubber hose, and it ages slowly in engine-bay heat. The trade-offs are that standard silicone swells when soaked in oil or fuel, and it cuts more easily than rubber on a sharp edge.

A straight hose follows only gentle curves. Bent tighter, it flattens on the inside of the curve and loses bore, so a moulded bend is the right part for a real change of direction.

Choose by bore, length and resistance:

• Bore: small sizes such as 5, 6.5, 8 or 13 mm suit vacuum, breather and overflow lines. Sizes such as 51, 63, 76 and 102 mm suit intake and charge pipes.
• Length: mostly 1 m, with some 50 cm lengths, such as the 57 mm petrol- and oil-resistant hose.
• Petrol and oil resistance: resistant versions, such as 8, 16 and 19 mm, suit breather and catch-tank lines. Fuel feed and return lines need hose made and rated for fuel pressure.
• Colour: black or blue silicone, with some intake hoses in red.
• Other items: hose kits with four clamps, vehicle-specific intake boots and induction hoses named in the title, and plastic intake parts such as a 70 mm double-connection air inlet.

Cut with a sharp knife in one pass, keeping the cut square, or slip the hose over a spare pipe and cut against it. Avoid saws, which leave a ragged edge that will not seal. Check that the bore fits the pipe snugly, since a loose hose will not seal under any clamp.

Use smooth-band clamps, route the hose away from exhaust heat and sharp brackets, and leave a little slack for engine movement. At each service, look for swelling, soft spots and cuts at the clamps.