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Jake
Jake, Automotive Technician
Category: Mitsubishi
Satisfied Customers: 3900
Experience:  Experienced collision repair technician, Pulaski Tech graduate and DSM hobbyist.
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Mitsubishi Montero LS: have a 2001 montero xls 3.5L 4w. started

Customer Question

have a 2001 montero xls 3.5L 4w. started getting the chirping sound from abs system after lost all the fluid and refilled it. sometimes went away. no one could find the problem. went on for a couple of years. last week everything was running fine when a high pitched whine started. again mechanic could'nt tell what was making noise. I hit the brake and it was completely stiff (engine running). then the pedal relaxed and went to the floor. while I was still pushing the pedal it slowly "pumped" the pedal back up, lifting my foot. it would hold a few seconds then relax and go down. this process continued. Mech thought it was the sensor on the left front based on codes so we replaced it but now get error codes for the master abs. HELP!
Submitted: 2 years ago.
Category: Mitsubishi
Expert:  Jake replied 2 years ago.
hey there, are you hearing the squeak under at the dash/firewall area when you press the brake pedal? weird pedal sensations and difficulty stopping? or do you also get the noise not pressing the pedal?
Let me know please as there really is 2 probable causes here.
Expert:  Jake replied 2 years ago.
Since you seem to have stepped away I will explain both here.
The first and most common failure points we see on these hydraulic brake systems is the accumulators fail. When this happens you will get a screeching or chirping sound that sounds like it's coming from the dash that's followed by difficulty stopping and even pulsing pedal sensations. This repair is relatively simple and inexpensive, parts and labor come to about $200.
The other possibility is obviously the master ABS unit your mechanic mentioned, which is called the HBB (Hydraulic brake booster). Now while you can get abnormal noises from the booster assembly it's more common that they simply cause shuddering when trying to brake and poor stopping. You also will get abnormal pedal operation.
So at this point If you have chirping when braking and no way to properly test the HBB unit with a scan tool. I would consider having him replace the accumulator to see if that solves the problem.