brake booster or master cylinder
#12
08-04-2019 | 09:28 PM
Recovery Vehicle
Joined: Nov 2011
Posts: 1,140
Likes: 115
From: Traverse City, MI
This video describes how the brakes feel when the master cylinder is going out.
https://www.roverparts.com/resources...-discovery-ii/
https://www.roverparts.com/resources...-discovery-ii/
#13
08-04-2019 | 10:02 PM
4wd Low
Joined: Aug 2019
Posts: 12
Likes: 1
Master cylinder going bad.
The usual test is to pump up the brakes, press your foot on the brake pedal and hold it, if it goes to the floor it is usually bad. (engine off)
If you can pump them back up but it fades again then it is the master cylinder.
The hissing sound you hear is the vacuum leaking out. The brake booster uses engine vacuum to multiply the pressure you put on the brake pedal.
If the booster goes bad you can pump up the brakes by pumping the pedal repeatedly.
If pumping up the brakes does not work then the master cylinder is bad.
Start the engine, have your wife pump up the brakes while you look/feel/listen for the hiss, it will most likely be coming from the hose that goes from the MC to the engine.
Check for cracks, replace that hose if needed.
If that is all good then replace the MC.
The usual test is to pump up the brakes, press your foot on the brake pedal and hold it, if it goes to the floor it is usually bad. (engine off)
If you can pump them back up but it fades again then it is the master cylinder.
The hissing sound you hear is the vacuum leaking out. The brake booster uses engine vacuum to multiply the pressure you put on the brake pedal.
If the booster goes bad you can pump up the brakes by pumping the pedal repeatedly.
If pumping up the brakes does not work then the master cylinder is bad.
Start the engine, have your wife pump up the brakes while you look/feel/listen for the hiss, it will most likely be coming from the hose that goes from the MC to the engine.
Check for cracks, replace that hose if needed.
If that is all good then replace the MC.
When I push the brake when the car is off, it is firm.
When I push the brake when the car is on, I hear a hiss(?) near the brake pedal. Bad booster?
I really want to make sure it is the booster before spending $600+ on a new one.
Thanks for your help.
#14
12-04-2019 | 09:10 PM
1st Gear
Joined: Dec 2019
Posts: 1
Likes: 0
Hi
got a problem with my Disco 2 brakes, she’s a 2000 v8.
pedal a very spongey with some brakes at the end of the travel, if I stamp on the pedal, it goes rock hard and I have no brakes, also noticed a squeaking/ whistle noise when I squeeze the pedal gently, sounds like it’s coming from inside the car.
got a problem with my Disco 2 brakes, she’s a 2000 v8.
pedal a very spongey with some brakes at the end of the travel, if I stamp on the pedal, it goes rock hard and I have no brakes, also noticed a squeaking/ whistle noise when I squeeze the pedal gently, sounds like it’s coming from inside the car.
#15
12-06-2019 | 11:43 PM
Recovery Vehicle
Joined: Feb 2009
Posts: 1,151
Likes: 30
From: Denver, CO
Hi Gary,
A bad booster will not not have the braking power, you normally feel. I swapped a new master cylinder in and it didn't change my pedal feel. Hard pedal with significant reduced braking power is a bad booster. Also my front calipers would not retract and burned up my front rotors. I installed a used booster a few years back and it works fine. Buying new on the booster is not necessary. Get a used one on eBay.
Bosshogt
A bad booster will not not have the braking power, you normally feel. I swapped a new master cylinder in and it didn't change my pedal feel. Hard pedal with significant reduced braking power is a bad booster. Also my front calipers would not retract and burned up my front rotors. I installed a used booster a few years back and it works fine. Buying new on the booster is not necessary. Get a used one on eBay.
Bosshogt
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