C300 Air Leak Noise when brakes NOT engaged.
Thread Starter
Junior Member
Joined: Feb 2012
Posts: 40
Likes: 0
'08 C300 4Matic
C300 Air Leak Noise when brakes NOT engaged.
G'day lads..
I just picked up a '08 C300 with low KM in great condition but have one small problem/annoyance.
I noticed an almost air leak like sound. Kind of like what you would hear with air in the coolant system. It is coming from the left side of the engine bay which I believe is where the brake master cylinder is.
If you step on the brakes, sound is gone. Soon as you release the brakes sound is back.
Looking at the maintenance records the brakes were bled only 3 months before I bought it, but what are peoples opinions? Do it again? Brake pedal feel doesn't seem off so I'm not sure if that is it.
Hoping to get some ideas before I look into it further.
I just picked up a '08 C300 with low KM in great condition but have one small problem/annoyance.
I noticed an almost air leak like sound. Kind of like what you would hear with air in the coolant system. It is coming from the left side of the engine bay which I believe is where the brake master cylinder is.
If you step on the brakes, sound is gone. Soon as you release the brakes sound is back.
Looking at the maintenance records the brakes were bled only 3 months before I bought it, but what are peoples opinions? Do it again? Brake pedal feel doesn't seem off so I'm not sure if that is it.
Hoping to get some ideas before I look into it further.
Member
Joined: Feb 2010
Posts: 204
Likes: 3
AV6
G'day lads..
I just picked up a '08 C300 with low KM in great condition but have one small problem/annoyance.
I noticed an almost air leak like sound. Kind of like what you would hear with air in the coolant system. It is coming from the left side of the engine bay which I believe is where the brake master cylinder is.
If you step on the brakes, sound is gone. Soon as you release the brakes sound is back.
Looking at the maintenance records the brakes were bled only 3 months before I bought it, but what are peoples opinions? Do it again? Brake pedal feel doesn't seem off so I'm not sure if that is it.
Hoping to get some ideas before I look into it further.
I just picked up a '08 C300 with low KM in great condition but have one small problem/annoyance.
I noticed an almost air leak like sound. Kind of like what you would hear with air in the coolant system. It is coming from the left side of the engine bay which I believe is where the brake master cylinder is.
If you step on the brakes, sound is gone. Soon as you release the brakes sound is back.
Looking at the maintenance records the brakes were bled only 3 months before I bought it, but what are peoples opinions? Do it again? Brake pedal feel doesn't seem off so I'm not sure if that is it.
Hoping to get some ideas before I look into it further.
i just noticed the same problem with my car. I Think its a leaking airhose or leaking master cylinder. I am going to take it to the dealer in a month because that is when my service is due.
Thread Starter
Junior Member
Joined: Feb 2012
Posts: 40
Likes: 0
'08 C300 4Matic
I've read quite a few people having a leaking booster/maserter cylinder/boot with Mercedes. I can't say I've ever had a brake related leak in a single other vehicle I've owned.
I find it a bit odd.
I find it a bit odd.
Member
Joined: Feb 2010
Posts: 204
Likes: 3
AV6
yup. i just noticed the hissing sound this morning. when i press the pedal a bit. the noise dissappear and when i release fully its back. I think its still safe to drive since its not leaking when i depress the pedal. The only thing that nmight be a problem is the leak sucking in dust causing excessive wear. oh well, im going to bring it in dealer in a month.
Newbie
Joined: Nov 2006
Posts: 8
Likes: 0
i too have hissing brake noise
I have an 2008 w204 30k miles and have the same hissing noise, when I press the brake the noise goes away. I am under warranty and plan to eventually take it in. Who has had this issue fixed, and what was it? 
Thread Starter
Junior Member
Joined: Feb 2012
Posts: 40
Likes: 0
'08 C300 4Matic
I find it pretty odd how many people have a leaking brake booster on their 2008 W204.
Super Member
Joined: May 2010
Posts: 816
Likes: 21
2008 W204
I had the issue, took it in, they replaced the brake booster and it was gone.
Trending Topics
MB World Stories
The Best of Mercedes & AMG
Manual Mercedes? 6 Times Sindelfingen Let Drivers Have All The Fun
Verdad Gallardo
Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren
Verdad Gallardo
8 Classic Boxy Mercedes Designs That Have Aged Like Fine Wine
Verdad Gallardo
Flawlessly Restored Mercedes 190E Evo II Heads to Auction
Verdad Gallardo
Electric Mercedes C-Class Unveiled: 11 Things You Need to Know
Verdad Gallardo
Mercedes EQS Gets A Major Update: Everything You Need to Know
Verdad Gallardo
5 Underrated Mercedes-Benz Models That Don't Get the Love They Deserve
Verdad Gallardo
Mercedes 300D Has Pushed Well Past 1 Million Miles and It Ain't Stopping
Verdad Gallardo
