Hydraulic Brake System Diagnosis

	Step	Action	Yes	No
	DEFINITION: This diagnostic table is designed to diagnose ONLY the components of the HYDRAULIC brake system in order to determine if the HYDRAULIC brake system is operating properly. You will be directed by the appropriate Symptom table to go to other brake system diagnostic tables as appropriate.
	1	Were you sent here from a Hydraulic Brake Symptom table?	Go to Step 2	Go to Symptoms - Hydraulic Brakes
	2	Inspect and adjust the brake fluid level in the brake master cylinder. Brake Master Cylinder Reservoir Filling Was the brake fluid level low?	Go to Step 5	Go to Step 3
	3	1. Inspect the brake fluid for the following conditions, indicating brake fluid contamination: Fluid separation, indicating two types of fluid are present – Swirled appearance – oil-based substance – Layered appearance – silicone-based substance Fluid discoloration – Cloudy appearance – moisture – Dark appearance/suspended particles in fluid – dirt, rust, corrosion, brake dust 2. Inspect the master cylinder reservoir cap diaphragm and the reservoir-to-master cylinder grommets for swelling, indicating fluid contamination. Do any of the above conditions exist?	Go to Step 4	Go to Step 10
	4	1. Flush the hydraulic brake system. Hydraulic Brake System Flushing 2. If the brake fluid WAS contaminated with an oil-based or a silicone-based fluid, indicated by fluid separation and/or a swollen master cylinder reservoir cap diaphragm and/or swollen reservoir-to-master cylinder	Go to Step 8	—

	Step	Action	Yes	No
		grommets, perform the following steps. Refer to the procedures indicated. 2.1. Remove ALL of the following components listed. Each component contains internal rubber seals/linings which have been contaminated. 2.2. Clean out the hydraulic brake pipes using denatured alcohol, or equivalent. 2.3. Dry the brake pipes using non-lubricated, filtered air. 2.4. Repair or replace ALL of the following components listed. Each component contains internal rubber seals/linings which have been contaminated. Brake Master Cylinder Replacement - With Power Brake Booster and Electronic Brake Control Module Brake master cylinder reservoir: Clean the brake master cylinder reservoir using denatured alcohol, or equivalent, then dry the reservoir using non-lubricated, filtered air, or if necessary, replace the brake master cylinder reservoir. Replace the brake master cylinder reservoir cap diaphragm. Front Brake Hose Replacement Rear Brake Hose Replacement Front Brake Caliper Overhaul or Front Brake Caliper Replacement Rear Brake Caliper Replacement 3. If the brake fluid was NOT contaminated with an oil-based fluid, but WAS contaminated with water or dirt, rust, corrosion, and/or brake dust, replace the brake master cylinder reservoir cap diaphragm which may have allowed moisture or dirt to enter the system. 4. Refill and bleed the hydraulic brake system. Hydraulic Brake System Bleeding Did you complete the operation and any required repairs and/or replacements?
	5	1. Inspect the following hydraulic brake system components for external fluid leaks. Repair or replace any of the components found to be leaking brake fluid. Refer to the appropriate procedures: Brake Master Cylinder Replacement - With Power Brake Booster and Electronic	Go to Step 6	Go to Step 10

	Step	Action	Yes	No
		Brake Control Module Front Brake Hose Replacement Rear Brake Hose Replacement Brake Pipe Replacement Front Brake Caliper Overhaul or Front Brake Caliper Replacement Rear Brake Caliper Replacement 2. If you repaired or replaced any of the brake system components listed, bleed the hydraulic brake system. Hydraulic Brake System Bleeding While bleeding the hydraulic brake system, observe for the following conditions: The presence of air in the system at a bleeder valve location other than at the repair location, except if the brake master cylinder was replaced An unrestricted and even flow of brake fluid per axle during the bleeding procedure Did you find and correct a condition?
	6	Was there air in the system at a bleeder valve location other than at the repair location, except if the brake master cylinder was replaced?	Go to Step 17	Go to Step 7
	7	Was the flow of brake fluid unrestricted and even per axle during the bleeding procedure?	Go to Step 8	Go to Step 9
	8	Inspect the hydraulic function of the brake calipers for proper operation. Hydraulic Brake Component Operation Visual Inspection Was the hydraulic function of the brake calipers operating properly?	Go to Step 17	Go to Step 12
	9	Was the flow of brake fluid restricted or uneven through front axle hydraulic components during the bleeding procedure?	Go to Step 13	Go to Step 10
	10	Inspect the hydraulic function of the brake calipers for proper operation. Hydraulic Brake Component Operation Visual Inspection Was the hydraulic function of the brake calipers operating properly?	Go to Step 13	Go to Step 11
	11	Determine if the brake caliper is restricting the flow of brake fluid and/or not operating properly. Brake Caliper Inspection Was the flow of brake fluid unrestricted and did the caliper piston move freely?	Go to Step 15	Go to Step 12

	Step	Action	Yes	No
	12	Repair or replace any brake caliper that was not operating properly. Refer to the appropriate procedure: Front Brake Caliper Overhaul or Front Brake Caliper Replacement Rear Brake Caliper Replacement Did you complete the repair and/or replacement?	Go to Step 17	—
	13	Bleed the hydraulic brake system to observe for the presence of air in the system and to observe for an unrestricted and even flow of brake fluid per axle during the bleeding procedure. Hydraulic Brake System Bleeding Was there air in the system?	Go to Step 17	Go to Step 14
	14	Was the flow of brake fluid unrestricted and even per axle during the bleeding procedure?	Go to Step 17	Go to Step 15
	15	1. Inspect the hydraulic brake pipes and flexible brake hoses for signs of a fluid restriction; such as being bent, kinked, pinched or damaged. Brake Pipe and Hose Inspection 2. Replace any of the hydraulic brake pipes and/or flexible brake hoses found to be bent, kinked, pinched, or damaged. Refer to the following procedures as necessary: Front Brake Hose Replacement Rear Brake Hose Replacement Brake Pipe Replacement 3. If none of the hydraulic brake pipes or flexible brake hoses were visibly bent, kinked, pinched, or damaged, replace the hydraulic brake flex hose at the restricted location. Did you find and correct a condition?	Go to Step 17	Go to Step 16
	16	1. Inspect the hydraulic brake system components for brake fluid seepage at a seal and/or fitting location, which may have drawn air into the system. 2. Inspect the hydraulic brake system components for evidence of a recent repair, which may have introduced air into the system. 3. Repair or replace any of the components found to be installed incorrectly or seeping brake fluid.	Go to Step 17	Go to Step 3

Step	Action	Yes	No
	Did you find and correct a condition?
17	Install or connect components that were removed or disconnected during diagnosis. Did you complete the operation?	Hydraulic Brake System OK Return to Symptom Table	—