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© 2012 Delmar, Cengage Learning© 2012 Delmar, Cengage Learning

Automotive Plumbing: Tubing and Pipe

Chapter 24


Objectives• Describe the different types of tubing used on

automobiles• Understand the different types of tubing

connections• Repair damaged tubing


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


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



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)



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)


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



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


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


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


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



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


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


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




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



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


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


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


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