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Automotive Plumbing: Tubing and Pipe
Chapter 24
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Objectives• Describe the different types of tubing used on
automobiles• Understand the different types of tubing
connections• Repair damaged tubing
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Introduction• Tubing and pipe
– Found on automobiles and on shop equipment• This chapter covers:
– Tubing and pipe service– Different types of plumbing parts– Connectors used with tubing and pipe
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Tubing• Often called “line”
– No threads at its ends– Can be made of copper, steel, or plastic
• Manufacturers choose the least expensive alternative to do the job safely
• Copper tubing – Can be soft or rigid– Work hardens
• Plastic – Used for vacuum or oil pressure lines
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Tubing (cont'd.)• Steel tubing
– Galvanized to prevent rust– Double-walled when used for brake lines– Armor: Steel coil around outside of a break tube
• Tube fittings– Many types of fittings join tubing to components– Connectors are used between tubing and parts
(e.g., oil pump)
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Flared Connections• Used when two steel fuel lines are connected
– Flare connection is suited for high-pressure applications
– Must be used for brakes or power steering• Two kinds of flares:
– Double flare (SAE)– Bubble flare (ISO)
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Flared Connections (cont'd.)• SAE-type double flare
– Used with an inverted flare nut• SAE flare: can be a either a single or double
– Single flare: not used on small automotive tubing• ISO flares: used since the early 1980s
– Bubble is formed in the line near its end
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Compression Fittings• Compression fittings: flareless fittings
– One kind uses a brass sleeve called a ferrule• To install a compression fitting:
– Slide nut onto tubing– Slide the sleeve onto the tubing– Insert the tubing as far into the fitting as possible– Tighten one and a fourth turns after both fittings
have contact
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Compression Fittings (cont'd.)• Characteristics
– Should not be used on high-pressure applications
– Can also be used with rigid plastic tubing– Double compression fitting: no separate sleeve
but compresses front part of nut against tubing– O-ring connections: used to seal fittings
• Unions – Join two pieces of tubing together
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Pipe Fittings• Pipe threads are used for:
– Heater outlets– Oil gallery– Coolant drain plugs– Oil and coolant temperature sending units– Compresses air lines in the shop
• Fittings on copper, brass, or iron pipe – Use tapered threads
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Pipe Fittings (cont'd.)• Characteristics
– Size of pipe thread • Determined by the size of the piece of pipe
– Pipe coupling• Joins two pipes
– Street elbow• Male thread on one end
– Close nipple • Tapered threads on each end that join in middle
– Long nipple • Plain pipe separates the threads
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Shutoff Valves• Also called draincocks
– Often found on the bottom of a radiator– Turning end of valve opens or closes it– Plastic radiator tanks usually have a plastic drain
valve
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Tubing Service• Tubing comes in precut lengths with flare fittings• Considerations
– Do not kink bulk tubing when unrolling– Use a tubing wrench or flare nut wrench to
loosen a flare fitting– Damaged steel fuel lines can be cut and repaired
• New lines fabricated with a flaring tool
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Tubing Service (cont'd.)• Cutting tubing
– Cut square on the end– Tubing cutter is tightened against tubing then
rolled around it– Remove burrs
• Bending tubing– Too sharp of a bend will cause a kink– Install fittings and flare both ends before bending
tubing
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Tubing Service (cont'd.)• Bending spring: installed over the tubing
– Prevents kinking• Steel lines: should not have long, straight runs• Long runs: should be supported with clamps• Flaring the ends of tubing
– Double flare or an ISO flare• Double flaring is a two-step procedure
• ISO flaring– Bubble or ridge is formed in the line a short way
back from its end
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Installing Tubing• When installing tubing
– Leave first fitting loose • Union repairs
– Union is used to repair a damaged line• Better repair than hose for high-pressure lines
• Using hoses to repair tubing– When a section of steel fuel line is damaged, it is
best to replace it and its flared ends and fittings
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Transmission Oil Cooler Line Repairs
• Union– Best repair for a transmission cooler line
• Kinks are often repaired with hose– If rubber hose is used: flare both ends of the
metal tubing– Edges of a double flare can cut the rubber hose
over time
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Nylon Fuel Injection Tubing• Nylon line is connected to steel line
– Push connector is used– Some nylon lines are coupled together with a
“spring lock” connector– There are two O-rings on the male coupling– If the garter spring is damaged or missing, it can
be replaced in the coupling
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Pipe Service• Pipe is cut with a pipe cutter
– Resembles a large tubing cutter• Pipe dies
– Form threads on the outside of the pipe• Thread sealer
– Used between threads• After hand tightening pipe
– Tighten further a minimum of two and a half turns