22 · Diagnostics

Brake pedal hard

Make: Fiat
Model: Doblò Factory Service Manual
Year: 2000–2010
Section: Braking system › Brake pedal hard

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Fault diagnosisBrake pedal hard

BRAKE PEDAL HARD

0	PRELIMINARY CHECKS	All OK	Problems met	Operation
		Results of the tests
	Resting the foot on the brake pedal, check that the pedal sinks when the engine is started, because of the vacuum in the braking circuit		Absence of or partial servo assistance	Continue to Step 1
1	CHECK ON VACUUM PIPE	All OK	Problems met	Operation
	Check vacuum pipe: must not be bent or damaged	Continue to Step 2	Pipe bent	Restore the correct geometry
	Check vacuum pipe: must not be bent or damaged	Continue to Step 2	Pipe damaged	Replace the damaged pipe Op. 3330D24
2	CHECK NON-RETURN VALVE	All OK	Problems met	Operation
	Check that the non-return valve is working properly	Continue to Step 3	Faulty operation	Replace check valve Op. 3330D20
3	CHECK ON SERVO BRAKE HYDRAULIC CIRCUIT	All OK	Problems met	Operation
	Check the brake servo pneumatic circuit In particular: that there are no air leaks that there are no seizures or stiffness	Continue to Step 4	Brake servo with leaks	Replace the pump/ servo brake assembly Op. 3330D02
		Continue to Step 4	Brake servo operation is jerky	Replace the pump/ servo brake assembly Op. 3330D02
4	CHECK ON VACUUM	All OK	Problems met	Operation
1.2 8v	Check the vacuum level in the servo brake system Under particular conditions of use, low engine rpm with excessive use of the brakes, the vacuum for operating the servo brake may be insufficient resulting in hardening of the brake pedal. It is pointless replacing the servo unit.	Continue to Step 5	Value incorrect	Eliminate blockages in the manifold
1.2 8v		Continue to Step 5	Value correct	Replace the pump/ servo brake assembly Op. 3330D02If pedal stiffness persists Continue to Step 5
1.9 DIESEL	Check the vacuum level in the servo brake system Under particular conditions of use, low engine rpm with excessive use of the brakes, the vacuum for operating the servo brake may be insufficient resulting in hardening of the brake pedal. It is pointless replacing the servo unit.	Continue to Step 5	Value incorrect	Replace the vacuum unit Op. 3330D30
1.9 DIESEL		Continue to Step 5	Value correct	Replace the pump/ servo brake assembly Op. 3330D02. If pedal stiffness persists Continue to Step 5
5	CHECK ON WHEEL CYLINDERS AND BRAKE PUMP	All OK	Problems met	Operation
	Check that the wheel cylinders and brake pump are not seized Check that one or more wheels do not remain braked	Continue to Step 6	Seizure of the pump	Replace the pump/ servo brake assembly
			Seizure of a caliper	Replace the seized caliper Op. 3310A30
			Seizure of a wheel cylinder	Replace the seized cylinder Op. 3320B20
			The car remains braked	Remove the servo/pump assembly and adjust the projection of the pushrod
			The car remains braked at the rear	Repair the handbrake
6	CHECK WITH DIAGNOSTIC EQUIPMENT	All OK	Problems met	Operation
1.9 DIESEL	Connect diagnostic equipment (Examiner or other instruments) to the diagnostic socket. Verify: that there are no faults in the ABS control unit that the ABS and EBD warning lights are working	Continue to Step 7	An error is detected in the control unit	Continue following the instructions for the diagnostic equipment
1.9 DIESEL		Continue to Step 7	Lack of dialogue with the control unit	Restore the connection between the engine management control unit and the diagnostic connector See E7020 ABS
7	CHECK ON CORRECT OPERATION	All OK	Problems met	Operation
	Test the vehicle before delivery to the customer, to check that the fault is no longer present The test is essential, as the braking system involves a safety feature of the car		Fault persists	Search for the fault starting from another symptom'

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Parts & tools for this job For 2000 Fiat Doblò

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