Test di esercitazione ASE A5 freni

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Tutte le 15 domande a colpo d'occhio

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1. 1. A dual, or split, master cylinder is used so that:

   • A. the pedal takes less effort to push
   • B. the rear brakes always get the same pressure as the front brakes
   • C. a leak in one circuit still leaves the other circuit able to stop the vehicle
   • D. the brake fluid never has to be replaced
   Mostra risposta e spiegazione

   Risposta: C. a leak in one circuit still leaves the other circuit able to stop the vehicle

   A dual master cylinder has two pressure chambers feeding two separate circuits, split either front to rear or diagonally. Lose one circuit and the other still works, but only about half the braking is left, the pedal travels much farther before it does anything, and the stopping distance grows. A pressure differential switch senses the imbalance and turns on the brake warning lamp, so a warning lamp with a long pedal is a failed circuit to be found, never a top off job.

2. 2. Complete the sentence.

   Brake fluid meeting DOT 3 and DOT 4 is hygroscopic, which means it absorbs _____ from the air over time. That lowers the fluid's _____, so hard repeated braking can boil it and leave the pedal soft just when it is needed most.

   Opzioni per lo spazio 1: moisture, heat, copper, oxygen

   Opzioni per lo spazio 2: viscosity, color, boiling point, freezing point

   Mostra risposta e spiegazione

   Risposta: moisture, boiling point

   Glycol based fluid pulls water vapor in through hoses, seals and the reservoir cap, and even a small percentage of water drops the boiling point sharply. Liquid fluid does not compress, but the vapor bubbles that form when it boils do, which is why fluid that was fine on flat roads can give a long soft pedal on a mountain descent. That is the whole reason manufacturers publish a fluid replacement interval by time rather than by mileage.

3. 3. Which of the following statements about brake fluid are true?

   Seleziona tutte le risposte corrette.

   • A. DOT 3 and DOT 4 are glycol based and pull moisture out of the air
   • B. Water absorbed by the fluid raises its boiling point
   • C. DOT 5 is silicone based and must not be mixed with DOT 3 or DOT 4
   • D. Spilled glycol based fluid can damage painted surfaces
   • E. An opened container of brake fluid can sit uncapped on the bench with no effect on it
   Mostra risposta e spiegazione

   Risposta: A. DOT 3 and DOT 4 are glycol based and pull moisture out of the air, C. DOT 5 is silicone based and must not be mixed with DOT 3 or DOT 4, D. Spilled glycol based fluid can damage painted surfaces

   DOT 3, DOT 4 and DOT 5.1 are glycol based and hygroscopic. DOT 5 is silicone, does not absorb water and is not compatible with the glycol fluids, so mixing them is a system contamination, not a top off. Water lowers the boiling point rather than raising it. Glycol fluid strips paint, so wipe spills immediately and flush with water. And an open container starts absorbing moisture right away, which is why you use fluid from a sealed container and cap what is left.

4. 4. A brake pedal feels soft and springy, and it firms up when the driver pumps it. This most often means:

   • A. air is trapped in the hydraulic system
   • B. the master cylinder seals are bypassing internally
   • C. the rotors have excessive lateral runout
   • D. the parking brake cable is seized
   Mostra risposta e spiegazione

   Risposta: A. air is trapped in the hydraulic system

   Brake fluid does not compress, so a pedal that squashes has something in it that does, and that is air. Pumping compresses the trapped air enough to move fluid to the wheels, which is why the pedal firms up on the second and third push. Bleeding fixes the symptom, but find how the air got in first, because a hose, a loose fitting or a low reservoir that let the master cylinder suck air will simply put it back.

5. 5. Stopped at a light with steady foot pressure, the pedal slowly sinks toward the floor. There is no fluid on the ground and no wet spot at any wheel. The most likely cause is:

   • A. rotors with excessive thickness variation
   • B. a metering valve stuck open
   • C. glazed brake linings
   • D. master cylinder cup seals letting fluid bypass inside the cylinder
   Mostra risposta e spiegazione

   Risposta: D. master cylinder cup seals letting fluid bypass inside the cylinder

   A pedal that sinks under constant pressure means fluid is going somewhere. With no external leak, it is going past the master cylinder cup seals and back into the reservoir, so the level can look perfectly normal. Keep this separate from the spongy pedal: spongy and pumps up points at air, slowly sinking under steady pressure points at the master cylinder. Rotor and lining problems change how the vehicle stops, not whether the pedal holds.

6. 6. Complete the sentence.

   A _____ valve limits how much pressure reaches the rear brakes during a hard stop, so the lighter loaded rear wheels do not lock before the fronts. A _____ valve holds pressure back from the front disc brakes at low pedal effort, so the rear drum shoes have time to overcome their return springs.

   Opzioni per lo spazio 1: metering, residual pressure, proportioning, check

   Opzioni per lo spazio 2: metering, proportioning, bypass, load sensing

   Mostra risposta e spiegazione

   Risposta: proportioning, metering

   Both often live inside one combination valve along with the pressure differential switch that lights the brake warning lamp. The proportioning valve exists because weight shifts forward under braking and the rear tires lose grip. The metering valve exists because disc brake pads sit almost touching the rotor while drum shoes have to be pulled off their return springs first, so without it the front would grab before the rear did anything. Many newer vehicles handle rear pressure electronically through the ABS module instead of with a mechanical valve.

7. 7. No manufacturer bleeding sequence is available for a vehicle. Common practice is to start bleeding at the wheel farthest from the master cylinder and work toward the closest. The usual reason given is that:

   • A. the farthest wheel has the highest pressure in it
   • B. the longest line holds the most air, so clearing it first avoids pushing fluid back through circuits you already finished
   • C. the rear brakes need less fluid than the front brakes
   • D. starting at the closest wheel would damage the master cylinder
   Mostra risposta e spiegazione

   Risposta: B. the longest line holds the most air, so clearing it first avoids pushing fluid back through circuits you already finished

   The point of a sequence is to move air out in an orderly way instead of chasing it around the system. Two things matter more than the habit itself. The manufacturer's published sequence always wins where one exists, and on many vehicles with ABS the module has to be commanded through a bleed routine with a scan tool or trapped air will never come out of it. Also bench bleed a new master cylinder before installing it, because air sitting in the cylinder bore is very hard to push out afterward.

8. 8. A pulsation felt in the brake pedal only while braking is most directly caused by:

   • A. excessive lateral runout of the rotor
   • B. thickness variation across the rotor
   • C. air trapped in the caliper
   • D. a worn wheel bearing
   Mostra risposta e spiegazione

   Risposta: B. thickness variation across the rotor

   Thickness variation means the rotor is measurably thicker in some spots than others. As the thick spot passes between the pads, the caliper piston is pushed back, and that motion travels up the fluid column into your foot. Lateral runout is side to side wobble measured with a dial indicator, and by itself it does not move the pedal. It matters because the wobbling high spot keeps brushing the pads between stops and grinds thickness variation into the rotor over the following weeks, so runout found today is pulsation a month from now. Check runout with a dial indicator and thickness variation with a micrometer at several points around the rotor.

9. 9. On a floating caliper disc brake, the inboard pad is worn far more than the outboard pad. The most likely cause is:

   • A. brake fluid that is past its replacement interval
   • B. a restricted proportioning valve
   • C. caliper slides or bushings that are binding, so the caliper cannot move on its mounts
   • D. a rotor that is below minimum thickness
   Mostra risposta e spiegazione

   Risposta: C. caliper slides or bushings that are binding, so the caliper cannot move on its mounts

   A floating caliper has pistons on the inboard side only. The piston pushes the inboard pad against the rotor, and the reaction force slides the whole caliper body inward to pull the outboard pad in behind it. If the slides are dry, corroded or have swollen bushings, the caliper cannot move, so the inboard pad does nearly all the work and wears out first. Clean and lubricate the slides with the specified high temperature grease whenever pads are replaced. A different pattern, both pads worn and the wheel hot after a drive, points at a piston or a hose that is not releasing.

10. 10. On many duo-servo drum brakes, when does the star wheel self adjuster take up lining wear?

    • A. Every time the brakes are applied while moving forward
    • B. Only when the drum is removed and the star wheel is turned by hand
    • C. Whenever the engine is started
    • D. When the brakes are applied while the vehicle is backing up
    Mostra risposta e spiegazione

    Risposta: D. When the brakes are applied while the vehicle is backing up

    In that design the shoes float around slightly during a reverse stop, and that movement lets the adjuster lever climb one tooth and turn the star wheel. It is why a vehicle that is always parked nose out can develop a low pedal from underadjusted rear brakes, and why backing up and stopping a few times is a standard step after a drum brake job. Other designs advance the adjuster through the parking brake linkage instead, so on those the parking brake going unused causes the same low pedal. Either way, a self adjuster that is seized, installed on the wrong side or missing its spring stops adjusting entirely.

11. 11. In a duo-servo drum brake, which shoe does most of the stopping work when the vehicle is moving forward?

    • A. The secondary shoe, the one toward the rear of the vehicle
    • B. The primary shoe, the one toward the front of the vehicle
    • C. Both equally, because the wheel cylinder pushes them with the same force
    • D. Neither, because the parking brake strut carries the load
    Mostra risposta e spiegazione

    Risposta: A. The secondary shoe, the one toward the rear of the vehicle

    The wheel cylinder pushes both shoes out with equal force, but the drum is turning. It drags the primary shoe along with it, and that force passes through the adjuster link at the bottom into the secondary shoe, wedging it harder into the drum. This self energizing action is where duo-servo gets its stopping power. It is also why the secondary lining is usually the longer of the two, so on reassembly the shorter lining goes toward the front of the vehicle. Swap them and the brakes will feel weak and the linings will wear unevenly.

12. 12. Which steps belong in a basic function test of a vacuum brake booster?

    Seleziona tutte le risposte corrette.

    • A. With the engine off, press and release the pedal several times to use up any stored vacuum
    • B. Bleed the hydraulic system before any booster test can be considered valid
    • C. Hold steady pressure on the pedal and start the engine, expecting the pedal to drop slightly
    • D. Run the engine about a minute, shut it off, wait a minute, then check that the first one or two applications still feel assisted
    • E. Turn the master cylinder pushrod in until the pedal feels hard
    • F. Unplug a wheel speed sensor to isolate the booster from the ABS module
    Mostra risposta e spiegazione

    Risposta: A. With the engine off, press and release the pedal several times to use up any stored vacuum, C. Hold steady pressure on the pedal and start the engine, expecting the pedal to drop slightly, D. Run the engine about a minute, shut it off, wait a minute, then check that the first one or two applications still feel assisted

    The three real checks are depleting the reserve, watching for the pedal to drop when the engine supplies vacuum, and then testing whether the booster holds a reserve after shutdown. A pedal that does not drop means the booster is not getting vacuum or is not working, so check the hose and the check valve before condemning it. A booster that assists while running but has no reserve after shutdown usually has a leaking check valve or a leaking diaphragm. Pushrod length is a measured adjustment, not something you turn in until the pedal feels right, because a rod that is too long keeps the master cylinder ports covered and the brakes drag.

13. 13. The main purpose of an antilock brake system is to:

    • A. shorten the stopping distance on every road surface
    • B. remove the need to bleed the base brake system
    • C. keep the wheels from locking so the driver can still steer during hard braking
    • D. apply the brakes automatically when the driver reacts too slowly
    Mostra risposta e spiegazione

    Risposta: C. keep the wheels from locking so the driver can still steer during hard braking

    ABS senses a wheel about to lock and releases, holds and reapplies pressure at that wheel many times a second, which is the pulsing the driver feels. A rolling tire can still be steered, while a locked one just slides wherever momentum takes it. On loose gravel or deep snow a locked wheel builds a wedge of material ahead of it, so ABS can actually lengthen the stop there even though control is better. Two other points the test likes: ABS sits on top of the base brakes and cannot make up for worn pads or air in the lines, and automatic emergency braking is a separate system that happens to use the same hydraulic hardware.

14. 14. One wheel speed sensor circuit is suspected on a vehicle with ABS. Which checks belong in that diagnosis?

    Seleziona tutte le risposte corrette.

    • A. Replace the master cylinder before testing the sensor
    • B. Measure the sensor's resistance and compare it with the specification
    • C. Inspect the tone ring for chipped or missing teeth and for packed debris
    • D. Check the brake fluid level, because low fluid switches the wheel speed sensors off
    • E. Measure AC voltage at the sensor terminals while turning the wheel by hand
    Mostra risposta e spiegazione

    Risposta: B. Measure the sensor's resistance and compare it with the specification, C. Inspect the tone ring for chipped or missing teeth and for packed debris, E. Measure AC voltage at the sensor terminals while turning the wheel by hand

    A passive wheel speed sensor is a coil and a magnet. Spin the ring past it and it generates its own small alternating voltage, so a meter set to AC volts while you turn the wheel tells you whether it is producing a signal at all, and a resistance reading compared with spec tells you whether the winding is open or shorted. Just as important, a perfect sensor reads erratically if the tone ring is damaged or packed with rust and debris, so inspect the ring before condemning the sensor. Active sensor designs are powered and need a scan tool or an oscilloscope instead, so confirm which type you have first.

15. 15. Complete the sentence.

    A serviceable tapered roller wheel bearing is set by turning the hub while tightening the nut, which seats the rollers against their races. The nut is then backed off and retightened to leave a small amount of _____. Going tighter than that puts the bearing into _____, which makes it run hot and fail early.

    Opzioni per lo spazio 1: endplay, preload, runout, taper

    Opzioni per lo spazio 2: float, endplay, preload, backlash

    Mostra risposta e spiegazione

    Risposta: endplay, preload

    Turning the hub while you tighten is what makes the adjustment repeatable, because it forces the rollers into place instead of leaving them cocked. Always follow the manufacturer's procedure and torque values, and always use a new cotter pin. A bearing that is too loose gives excessive play at the top and bottom of the tire and a noise that changes when the vehicle is swerved gently side to side, since cornering loads and unloads each side. A bearing that is too tight has no room for oil film or heat growth and will fail quickly. Sealed hub units are not adjustable, so on those you measure play and replace the unit.

Cosa copre l'esame ASE A5 sui freni

A5 è uno degli esami della serie A per tecnici di autovetture e veicoli commerciali leggeri, stabilita dal National Institute for Automotive Service Excellence, l'ente statunitense noto come ASE. Resta dentro l'impianto frenante: diagnosi e riparazione dell'impianto idraulico, freni a tamburo, freni a disco, servofreni, cuscinetti ruota e freno di stazionamento, e impianti di controllo elettronico della frenata come l'ABS e i sistemi di stabilità costruiti sopra di esso. Si tratta di freni idraulici su auto e veicoli commerciali leggeri. I freni ad aria dei veicoli pesanti non fanno parte di A5, stanno nella serie per mezzi medi e pesanti, quindi una guida di studio sui CDL air brakes è il libro sbagliato per questo esame.

La certificazione richiede due cose, non una. Superi l'esame e dimostri due anni di esperienza pratica di lavoro. Una formazione formale pertinente può sostituirne una parte, e l'ASE pubblica le regole aggiornate su quanta. Inoltre la certificazione non dura per sempre. Scade e per tenerla valida devi rifare l'esame, ed è per questo che i tecnici intorno a te parlano di ricertificarsi invece che di essersi certificati una volta.

I numeri del giorno d'esame si spostano, quindi questa pagina non li cita. Quante domande hai, quanto tempo, con che punteggio si passa, quanto costa l'iscrizione e quali finestre d'esame sono aperte li fissa l'ASE e li aggiorna nel tempo. Prendili direttamente dall'ASE o dalla tua conferma di iscrizione, e considera che qualsiasi sito di esercitazione che li dichiari potrebbe non essere aggiornato.

Una cosa che conviene sapere prima di iniziare a studiare è il taglio delle domande. A5 punta molto sulla diagnosi più che sulla memoria, e una buona fetta di quesiti è scritta come il Tecnico A dice una cosa, il Tecnico B ne dice un'altra. Saper nominare i pezzi non basta. Devi sapere quale sintomo produce davvero ogni guasto, e quale di due spiegazioni entrambe plausibili si accorda con gli indizi che ti vengono dati.

Come usare questo assaggio

Queste 15 domande si distribuiscono sulle aree di contenuto di A5 invece di scavare in una sola. Ci sono domande di idraulica sulla pompa freni a doppio circuito, sul liquido freni e sulla sensazione del pedale, domande sui tamburi con schema duo-servo e sul registro automatico, domande sui dischi sullo stato del disco e sull'usura con pinza flottante, una domanda sul servofreno, una sui cuscinetti ruota e due sul controllo elettronico della frenata. Chiedono perché un sintomo succede, non solo come si chiama un pezzo, perché è quello che fa l'esame vero.

Fallo d'un fiato senza appunti, poi leggi la spiegazione di ogni domanda, comprese quelle che hai azzeccato. Tratta una risposta sbagliata come un argomento e non come un dato isolato. Se hai sbagliato la domanda sulle pulsazioni e quella sull'usura della pinza, siediti sull'assistenza ai freni a disco nel suo insieme invece di imparare a memoria due risposte.

L'abitudine di studio più utile per A5 è imparare i sintomi a coppie, perché è così che l'esame separa chi ha letto un libro da chi ha fatto il lavoro. Un pedale spugnoso e un pedale che affonda lentamente non sono lo stesso reclamo. Una pulsazione e un tiraggio non sono lo stesso reclamo. L'eccentricità del disco e la variazione di spessore del disco si misurano con strumenti diversi e causano cose diverse. Quando riesci a dire la coppia ad alta voce con parole tue, le domande con il Tecnico A e il Tecnico B smettono di essere insidiose.

Poi vai a metterci le mani. Smonta un tamburo, lavora su un registro a stella, fletti una guida della pinza, guarda un pedale abbassarsi quando il motore parte. I freni sono una di quelle aree dove cinque minuti su un veicolo sistemano un fraintendimento che un'ora di lettura non aveva sistemato.

Come StudyPDF crea test completi dal tuo materiale

Quindici domande ti mostrano quali parti dell'impianto frenante non sai ancora spiegare. Da sole non bastano per arrivare pronto, e una banca dati generica non sa da quale guida di studio parti né quali aree la tua officina vede di rado.

StudyPDF parte invece dal tuo materiale. Carichi la tua guida di studio A5, il capitolo sui freni di un manuale d'officina o le dispense del tuo corso, e Bo, l'agente di studio, crea test completi da quelle pagine esatte. Ogni domanda nasce dal tuo documento e ogni spiegazione rimanda a dove viene la risposta, così puoi controllare tu stesso la formulazione quando due fonti sembrano contraddirsi. Puoi generare test nuovi quante volte vuoi, restringerne uno a una sola area come la diagnosi dell'ABS o l'assistenza ai freni a tamburo, e vedere quali argomenti continui a sbagliare.

Per iniziare non serve un file. Se la tua guida di studio è rimasta in officina, nomina semplicemente un argomento, per esempio la diagnosi dell'impianto idraulico dei freni o l'assistenza ai freni a disco, e Bo ci scrive sopra un test. Inizi gratis.