When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
...I just watched this video & don't think my noise is this loud,but I've only listened to it inside the car.I will go under the hood tomorrow & see how it sounds from there
Yep, if you are hearing that you have a major problem with the brake master cylinder...it is leaking down and every time you turn on the key, it is pressurizing the system.
If you believe, pray it is not the the MC
Step 2. Bleed the MC
Step 3. Bleed the system
It leaks internally. The motor on the master cylinder pumps up pressure for abs operation. Abs and the vsc or DSC which ever you want to call it. Has to be able to apply the brakes not just cause the brakes to release. So it has to have its own source of pressure to do that.
Something else you guys can try . I have not driven the car the entire day
When I first took the YouTube video and had the key turned to " on" position
and you hear the low humming noise, it was in the morning
After the second try in the afternoon , I turned the car to the on position again and
the noise was gone .
BGw70 , what was your symptoms when you realized you had a failing Master cynider
I have no fluid leaks in my garage , no low brake fluid , no ABS lights , VSC light
No brake pedal to the floor issues
I had another SC and I recall it made the same low humming
Noise
A good sign that you are not leaking brake fluid!!!
As Cole explained, that sound is the pump and the pump is creating pressure, the built up pressure is stored in the accumulator.
My issue did involve a leak and it would take several hours for the system pressure to bleed down (overnight). In the morning, I would see a small puddle under the car. When I turned on the car, the MC would run for about 10-15 seconds and I could watch the brake fluid in the reservoir go down as the pump pressured the accumulator.
BTW, I know you said it not leaking but please be sure to confirm this by placing a small mark on the master cylinder reservoir with pencil or something. Place the mark after it has finished pressuring the system.
I have been reserarching the noise . Today the noise lasted about 10 seconds and then gone
I know what you mean about the reservoir emptying out and then when you pump the brakes , it comes back up
I wil do one more test as you have suggested
The car has 28K and my research also shows the SC 430 rarely have the MC go out but the car is 12 yrs old
Other than this low humming noise , the car has been bullet proof and really a joy
Leaking internally in a hydraulic system. it leaks from from the pressure side past the seal back into the reservoir. Here is picture to visualize how that would happen. You have no fluid loss just pressure loss. The fluid is essentially in a closed loop. Sorry I couldn't find a good picture of the accumulator. The theory is the same though.
10-31-15, 05:07 PM
