C207 2012 Brake Fluid Leak!

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MrGundam

Active Member
Joined
Jan 30, 2021
Messages
170
Location
Hampshire
Car
2012 C207 E350Cdi
Went out for quick 5 min drive to shops today and the brake pedal was feeling very spongey and travelling to floor. Once I got home I have brake fluid warning light.

After trying pedal a few times I can see a small puddle of fluid on the ROS.

Before I jack it up and take a look does anyone know what might usually go in this area? Brake flexi hose? Caliper itself?

Thought I would see if there are any known areas that might be good place to start.

Thanks
 
Probably a brake pipe has rotted through.
When mine went on my W204 (same chassis as yours) a competent local garage replaced both rear pipes for £250.
MB will charge a fortune because they will want to drop the rear subframe.
 
Well had a little dig about...

The undertray was full of muck around the area of the brake pipe leaking:

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Here is the result. After cleaning them up to take a look one is actually only surface but the other is shot:

x4IBv6z.jpg


What is frustrating is the the rest of the pipes are absolutely fine:

yyxVhg9.jpg

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yyxVhg9.jpg


So the question now, is it OK to replace the corroded section to good line, or does the entire thing need replacing? Annoyingly the one which has ruptured is the one going over the rear axle to the R/O/S.

I have brake flaring tools (DIN) from working on my VW campervan but if the entire thing has to be replaced as one I am not sure I could form all the intricacies.
 
Cut back to good pipe . Is the way to go.
 
Cut back to good pipe . Is the way to go.
I keep reading 'replace the entire pipe' so a bit torn at the moment. One friend into his motors says that any fixing mid line could affect the ABS system due to the flow. That sensitive on these?


Can anyone comment on if the rear sub needs dropping on a C207 to fit the pipe going to the ROS caliper? It seems to go over the rear axil and not sure how you would form all that and put it in as one.
 
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Cut back to good pipe . Is the way to go.

I am going for this route. My thinking is to cut a good meter out along the corroded part and replace with copper (no stress point there and will not make contact with anything) and join to existing steel pipes with bubble flares.

I see a lot of videos on Youtube with people using double flares on brakes but from my understanding most EU cars are bubble, is that correct?

I am planning on using these parts: Here, I assume those connectors are fine for bubble flares?

Thanks
 
Cut out as much as possible without making the job awkward and then replace with the pipe and joiners. Bleed and get someone to hold pressure on the brake pedal whilst you inspect for leaks or if you have a brake pedal clamp apply this and check after 5 mins to see if you have a good connection.
 
OK so my next clarification, if anyone is so kind is what flares to use for joining the existing good steel to the kunifer pipe I will be splicing.

I have ordered these brake pipe fixings here which include the various parts I need. I will use the male connectors with female joiners only.

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The description does not state which flare the joiner needs as I understand this is what dictates which tool to use (SAE or DIN).

YWafmR9.jpg

From what I gather if I was connecting to a MB brake union I would need DIN as most EU cars use this. However the fixings I am making will be stand alone and simply splicing in about a meter of pipe along the long run under the vehicle, and so not joining and MB unions.

I have searched around and seems that no sellers of the joint component state which flare is needed and don't show images of the inside mating surface. From the image above it is looking like I may need SAE tool (bottom left join fixing) to be able to make the 'bubble flare' but wondered if anyone has any experience with the ones like I ordered on Amazon here in the UK.

Thanks :)
 
OK so a little update on this.

Managed to make a nice section to good pipe using unions and DIN flares:

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Bled the system with a pressure bleeder and MB fluid, around all 4 corners starting with the furthest away twice to give a good flush and make sure absolutely no bubbles coming through.

Unfortunately I am midway through replacing some other bits in the engine (PCV, thermostat, turbo inlet gaskets, DPF pressure sensor) so couldn't start the engine and see how the brake pedal felt after the flush with brake servo assisting. I am hoping that the fluid didn't get too low when it burst and introduce air into the SBC needing a STAR bleed. I read that if the doors are all locked and not touched for an hour it releases the SBC reservoirs, but not sure how much I believe that, but did it anyway.

I did try the brake pedal with the key in position 1 but as I am new to the car I cannot remember how it should act. There is about 1/4 travel with no resistance, is that just because the servo isn't assisting with engine off?

I had a delve in my iCarsoft V2 and I must say I am not particularly impressed. So far it gives weird mileage readings for last DPF regen, doesn't tell me the % of DPF fill and despite advertising the ABS service area doesn't list my model and so cannot do that either.
 
You haven't got sbc.

Nice job 👍
 
So today I pressure bled and loosened the brake reservoir to ABS unit pipes and after a little while managed to purge the last of the air between the 2, happy days and a hard break pedal.

Here is the manky, rusted pipe that caused it all:

j59TeSq.jpg
 
My car failed MOT with corroded pipes. The tester said the whole pipe should be changed. Anyway the weather was bad and late autumn so I left them to do the job.
When I picked the car up and checked it later at home. Low and behold they put a join in missing the awkward (good) part of the pipe. Just what I would have done.
 
My car failed MOT with corroded pipes. The tester said the whole pipe should be changed. Anyway the weather was bad and late autumn so I left them to do the job.
When I picked the car up and checked it later at home. Low and behold they put a join in missing the awkward (good) part of the pipe. Just what I would have done.
I was originally going to replace the entire line and possibly all of them but decided to splice a section for a few reasons:
  1. To my surprise when I called a local MB Independent they said they would replace the bad section
  2. After checking all the remaining pipes they are in good condition
  3. MB service guidance actually allows up to 2 joins per pipe
  4. It was the straight section under the car which is easy to form
I did a lot of research to ensure I had the right tools to make the right flares with the right joining sections.

Bleeding was made so much easier with a pressure bleeder, great bit of kit.
 
Hi @MrGundam

Can I please just check a few things?

- What side of the car sill needs to be removed to access the brake pipes?
- How did you jack the car up and get the sill off?
- Did you use the XtremeAuto 3/16 unions from Amazon that you linked to in post#8 (are these DIN?)
- What pipe flaring tool did you use, and was it the same on the kunifer and steel? (I ask, because the steel pipe looks slightly thicker in the photos).
 
Hi @MrGundam

Can I please just check a few things?

- What side of the car sill needs to be removed to access the brake pipes?
- How did you jack the car up and get the sill off?
- Did you use the XtremeAuto 3/16 unions from Amazon that you linked to in post#8 (are these DIN?)
- What pipe flaring tool did you use, and was it the same on the kunifer and steel? (I ask, because the steel pipe looks slightly thicker in the photos).
Hi Greedy, sorry for delayed reply, long week.

- What side of the car sill needs to be removed to access the brake pipes?
The N/S (UK Passenger side) is where the pipes travel along the underside of the chassis.

- How did you jack the car up and get the sill off?
I have a 5 tonne jack. Use the mounting point near the ending and off the read diff. I then use axil stands on the Merc rubber mounts along the sills.

- Did you use the XtremeAuto 3/16 unions from Amazon that you linked to in post#8 (are these DIN?)
Yes. I contacted the seller and double checked if they are DIN or SAE. He said they use DIN flares which matches what I thought from the images (see ones I posted earlier)

- What pipe flaring tool did you use, and was it the same on the kunifer and steel? (I ask, because the steel pipe looks slightly thicker in the photos).
I actually purchased 1 DIN and 1 SAE as I didn't want to hold the job up should they be the other. Ended up using the DIN and it worked perfect on both the Copper Nickle and the OEM steel.

DIN Tool: Link
SAE Tool: Link
Pipe Cutter: Link
Deburr Tool: Link

Overall a fairly easy job. Few hiccup's bleeding the system as I needed to crack the 2 nuts going from the fluid reservoir to ABS unit to let air out, but I think this is because I lost a lot of fluid when the pipe burst. A lot of posts seem to indicate you need STAR to bleed the reservoirs, however I don't seem to have needed this and the brakes are spot on. The HOLD feature works fine.
 
Thank you very much MrGundam.

I have axle stands and a 3 ton jack, so I can do the same to get the car raised up so I can check this 👍
 

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