paperplane94

I have a 2002 ML320 (01/01) and just recently it started to have the Hissing under the dash. Seems to be pretty common
I confirmed it was the seal by pulling back the bellows cover and stopping the Hiss with my finger. Where can I buy just the seal?

The problem...I'm used to BMW parts where all you have to do is put the p/n in realoem.com where you can easily find the part.

But where can I find just the seal for the brake booster?
I don't think I can handle the expense of a brand new brake booster assembly. I did read on another thread somewhere where someone was able to buy just the seal only, but how?

If anyone can help me find the seal only I promise to document the fix with photos and make a DIY for this forum.

Maj. Dundee

Hissing at the booster is a common problem with ML's and there is no repair kit or gasket that is available. It is a sealed unit and the internal poppet valve is the problem and the booster must be replaced.

If you are careful you can remove the booster without disconnecting the master cylinder. Any year or model ML will fit as they all use the same part number.

If you are doing the work by yourself, remember that if the brake lines are disconnected, you must bleed the system where you do the repair or else the brake pedal will go to the floor which can cause an accident.

paperplane94

Thank you for the response, sucks that I can't just replace the seal only. Those brake boosters are super expensive.

ANd thank you for the advice, I know I will have to bleed the system its just that I'm used to bleeding 20 year old bmw's.

Are there any implications with bleeding the system, for example with the BAS or ABS synchronization? Any special tools like a pressure bleeder, or a computer to open the ABS valves or something like that?

Maj. Dundee

The system is the same as any other vehicle. Start with R/R then L/R, R/F then L/F. If you can get a pressure bleeder then things will be quicker.

paperplane94

Thanks for the clarification, I thought these systems needed something special but nope.
I hope others can benefit from this conclusion:
you cannot buy the seal alone to stop the hissing.
gotta buy the booster.

Thank You, Major Dundee!

Maj. Dundee

Try a junk yard in your area. $100-150 should do the trick.

paperplane94

OK. Will report back with results.

ML 500 mz

FYI...had brake booster replaced ('03 ML 500) in Feb by MB. Car was in for trans fluid change when hissing was discovered. Seems everyone in my family heard the hissing too, but me. Are you sitting down?... Part @ $798.00, labor @ $268.00.
Hope you solved your problem.

HEEMS

yes try the junk yard i had the same problem and got one for $150. they also have them refurbished u just have to look around

paperplane94

Well I cheaped it out instead

*this will only work if the seal hasn't totally disintegrated*









That's two 8in. zip-ties connected together and a flexible piece of plastic wrapped around the seal/boot close to where it meets the firewall.
You need to pull tightly enough on the zip-ties so that it compresses the seal. Don't cover over the vent holes (where the foam is) because it needs to "inhale" through there during application.

You shouldn't worry since the part I zip-tied is stationary so it won't come off. Worst case scenario: it comes off for some reason and you get the hissing and a lumpy idle due to the vacuum leak.


$150+ saved...Just to clarify you CANNOT buy the seal by itself, whole brake booster only.

Begin criticisms...NOW

AMG4FUN

If you buy the brake booster used, could you just switch the seal only? How difficult would that be?That would be the easiest, right?

paperplane94

That's the hard part.

100+ dollars?

AMG4FUN

Not exactly sure what you mean? I assume it would be easier to switch the seal only, and not the entire booster. I assumed this was possible, since people wanted to buy the seal only.

I just got a used booster (Grade A) for 65+shipping. I am thinking I will just take the seal off that unit and put it on the old booster already installed? Now, my question is: Is this something that can easily be done, or is there a good chance you brake the seal when trying to get it off and on?

I am not about to switch the brake booster myself, but the seal only might be DIY project I can comprehend.

paperplane94

All I know is that I can't find a used replacement brake booster with the seal for under 100 dollars around here, and this fix works.


If you replace it then I would imagine that if you damaged the old seal it wouldn't matter if you had another one. Some petroleum-free grease would help you slide it on after disconnecting the brake pedal from the booster. It's on there pretty tight. Make sure whatever grease you use is petroleum-free so that the rubber seal doesn't disintegrate.
You could even use some water-based personal lubricant like astroglide .


After that you should be good for another ten years! I wish Mercedes made a better product than this one, I would expect more out of them.

kyliesdad3

Paperplane94 - excellent pics. Thanks for that. Could you clarify the part where you said "Don't cover the vent holes (where the foam is)... Not sure what or where the foam is that you mean.

paperplane94

Sure.

When you first look at an untouched brake booster there is a white foam filter that surrounds the rubber boot next to the leaky booster seal. If you remove the white foam thing you will see holes cut out in the rubber boot.
This is where the brake booster 'breathes' in air when the pedal is depressed. I noticed it has trouble 'breathing' if the holes are covered up, so when you do the above fix make sure the plastic piece is skinny enough so it doesn't cover over the vent holes under the foam filter.

Basically just tighten the zip-ties around the booster seal and not the vent holes/ foam filter. The Zip- tie should be all the way down as close to the firewall/metal bracket as possible as shown in the photos above.

kyliesdad3

Update: I didn't use the the plastic strip method paperplane94 describes (couldn't find any of the stuff) but I did try silicon self adhesive "tape" strips on the area shown in his great pic. This stretchy, 3/4" wide silicon "tape" is the same stuff that those cheesy TV product pushers claim will fix any plumbing leak and is made by several manufacturers. At least one brand should be available at most home improvement stores.

One side of these silicon strips have cellophane on it and the other side doesn't. When you peel off the cellophane you're able to stretch this stuff so it will stick. It won't stick to anything except very smooth surfaces or itself. Boy does it stick to itself. Anyway, it's made an airtight seal since I wrapped about a foot of this stuff around the area 4 months ago shown in paperplane94's photo. The ML brakes work just like they used to before the air leak and don't hiss.

If/when the booster starts hissing again I'll repost so there'll be some idea of how long this scab job of mine held. Hey - if $10 worth of stretchy tape works for a temporary fix, why shell out $1,700 for another temporary fix?

kyliesdad3

That silicone stretch tape I put on only lasted a couple of months. It gave me enough time to locate a replacement booster from a yard ($100).

Thankfully I was able to replace the thing myself without having to remove any brake lines and corresponding brake bleeding. Once I was able to move the master cylinder away from the booster it went pretty fast. I unfastened the fuse box and just moved it a bit so that I could gain enough clearance for the MC to be pulled away. Unclipping the little clips that hold the metal brake lines made moving the MC easier too.

mwolf5682

Paperplane:

Great solution. I made mine out of a yogurt container and aluminum tape to hold the zip ties to the slippery plastic. Basically, make an overlapping collar with the zip strips taped to the outside and snug it up. Since it is a vacuum, keeping things contained should do the trick.

Hats off to you.

leshoiad

Hey boys, what is the effect of hissing brake booster. Is it possible the vacuum leak to be a reason of not properly working torbo? The car is ML 270 cdi 2002.......
What I'm talking about. When I press the brake pedal i have my brakes but when i release it it starts to hiss. Is this a mark that I have a vacuum leak and is it a couse of my not properly working turbo? Also at the engine start and running, everything with the engine is great but after my stopping and running again the engine is losing power. My logic is if I'm losing vacuum, there is not enaugh air steam within the vacuum system, at the same time my turbos' valve is vacuum operational.............. Am I right?

nickvardy

I've got the same issue and went down the route of getting a replacement servo off ebay. Problem is its from a W163 ML320 (petrol) rather than a W163 ML270 (diesel) that I have.

Are there any wise people out there that know if the servo might still be suitable? The part numbers are different so i'm guessing not but I can't seem to get a definitive answer anywhere and I suppose i'm being hopeful I can still switch the old out for the (not so) new.

I could try and switch the seal across but I fear I might damage it on removal.

Maj. Dundee

When we look up parts in M/B EPC, we can only view the U.S. market. The rest of the world has its own parts listing.

What is the part number on your old booster?

nickvardy

I've got it as A 163 430 01 30 for the booster taken from the ML320 whereas I believe the one on my ML270 CDI is A 163 430 06 30. Just need to find out for sure if the 01 vs the 06 means that the spare part I have is incompatible. Any help much appreciated.

Maj. Dundee

Before we go any further Update Your profile so we know what year 270CDI you have and where you live.

nickvardy

Have updated the info - hopefully that's worked. Cheers for the pointer!