W211 Brake Vacuum Hose

[FiveBellies]

Good evening, new member and my first thread. I hope I am posting this correctly, if not I do apologise. My question is to do with the vacuum hose that comes from the Brake Servo to the vacuum pump, on my 2008 Mercedes E320 Cdi W211, I have noticed a brown fluid on top of the connector to the pump, it's not soaking, but Is always there when I remove the engine cover. I have also noticed that the brake fluid level in the reservoir has gone down. I haven't removed the hose for further investigation yet, I thought I would post on here, to see if anyone could help with any information to help me further fault find etc. I've circled the connector in the picture that always has the fluid on. Any help would be appreciated. Thanks

 

[Peter103]

Hi there "Five Bellies" welcome to our Forum, I once knew a 'Billie Five Bellies',. Was that your Dad?
That looks to me like the Brake vacuum hose of a 211 but it shouldn't really get oiled up.
Fear not Mon Ami, someone will be along soon that may know a lot more about mechanicals, in fact if they didn't, what would be the point of all this at this ungodly hour of the a,m, enjoy the Forum and good luck.
P,s just a thought we've even got a "What did you eat today or get slim eat grim, thread on "Off Topic" you might find interesting, I get on there myself sometimes, checking up on the Fat Club, My mate Billie Five Bellies' went to the doctor and said, Dr, I need to lose some weight what can I do ? He thought for a bit and said "Stop eating Fatty"
Billie said what like Pork Sausages, Hamburgers, Big Fry ups Egg Bacon and Tomatos, lovely?, He said "No Fatty Stop Eating"

 

[FiveBellies]

Hi there "Five Bellies" welcome to our Forum, I once knew a 'Billie Five Bellies',. Was that your Dad?
That looks to me like the Brake vacuum hose of a 211 but it shouldn't really get oiled up.
Fear not Mon Ami, someone will be along soon that may know a lot more about mechanicals, in fact if they didn't, what would be the point of all this at this ungodly hour of the a,m, enjoy the Forum and good luck.
P,s just a thought we've even got a "What did you eat today or get slim eat grim, thread on "Off Topic" you might find interesting, I get on there myself sometimes, checking up on the Fat Club, My mate Billie Five Bellies' went to the doctor and said, Dr, I need to lose some weight what can I do ? He thought for a bit and said "Stop eating Fatty"
Billie said what like Pork Sausages, Hamburgers, Big Fry ups Egg Bacon and Tomatos, lovely?, He said "No Fatty Stop Eating"

Thank you Peter. I am no relation to Billie and I will be sure to look around the forum. Yes this is the Brake vacuum hose from a W211. I can only assume the it's coming from the connector as I can't see where else it would be coming from, but if it is coming from here then I would assume also that air can escape too. I did think maybe the master cylinder has a leak which is leaking the fluid from the reservoir into the Servo, which is then passing the fluid into the vacuum hose, where it is escaping by the pump as the fluid has maybe spoiled the seal. I've got a few jobs to do on this and will be starting on them this Saturday.

 

[Peter103]

Looks to me like this is one for Grober, he knows stuff, My mate MJ could know something positive they will show up eventually, stay cool. Watch the cricket India could lose!

 

[Tuercas viejas]

I'm not Grober but the guy from the "other side of the river".
That hose is connected to the brake servo unit.
The housing attached to the cylinder head is an engine driven vacuum pump --In old Brit trucking circles, it used to be called an exhauster-they both were the same thing, basically produce a vacuum .
Since you observe the brake fluid mysteriously going down,. the first thoughts are that the master cylinder is leaking from the pushrod end seal into the servo unit and the pump is slurping the fluid out and it is leaking at the slip connector which you have outlined.

Since this is a safety issue --an MOT failure in the making, the first step is to test the master cylinder for internal leakage .
To test it, have the engine running and the vehicle parked. Apply light pressure to the brake pedal and see if it sinks to the floor.
If it does the M/cyl is suspect , possibly & remotely the ABS brick!
Next turn off the engine and pump the brakes. You should feel the pedal tighten up as you se up the stored vacuum and it will feel like you are stepping on a brick. If it still sinks then you have serious brake problem. (hopeful not)
Now with your foot still firmly holding the pedal down start the engine, and the vacuum assist being restored by the pump will make the pedal sink a little under your foot pressure and then stop.
Try that out first.
All the best
Tuercas Viejas
a.k.a the dreaded old cocky MOT inspector of the 1970's who sent many old jalopies (Mexican/.Latino "Carcatchas" to the crusher .)

 

[FiveBellies]

I'm not Grober but the guy from the "other side of the river".
That hose is connected to the brake servo unit.
The housing attached to the cylinder head is an engine driven vacuum pump --In old Brit trucking circles, it used to be called an exhauster-they both were the same thing, basically produce a vacuum .
Since you observe the brake fluid mysteriously going down,. the first thoughts are that the master cylinder is leaking from the pushrod end seal into the servo unit and the pump is slurping the fluid out and it is leaking at the slip connector which you have outlined.

Since this is a safety issue --an MOT failure in the making, the first step is to test the master cylinder for internal leakage .
To test it, have the engine running and the vehicle parked. Apply light pressure to the brake pedal and see if it sinks to the floor.
If it does the M/cyl is suspect , possibly & remotely the ABS brick!
Next turn off the engine and pump the brakes. You should feel the pedal tighten up as you se up the stored vacuum and it will feel like you are stepping on a brick. If it still sinks then you have serious brake problem. (hopeful not)
Now with your foot still firmly holding the pedal down start the engine, and the vacuum assist being restored by the pump will make the pedal sink a little under your foot pressure and then stop.
Try that out first.
All the best
Tuercas Viejas
a.k.a the dreaded old cocky MOT inspector of the 1970's who sent many old jalopies (Mexican/.Latino "Carcatchas" to the crusher .)

Thank you for the advice, I will try them all out. Hopefully it is as initially thought with the master cylinder leaking into the servo unit. If this is the case, will I need to replace the servo unit? And can the master cylinder be repaired with a new seal kit or is it just easier to buy a new one? Also the hose, from the servo to the pump, can that be repaired/re-sealed?

 

[FiveBellies]

I'm not Grober but the guy from the "other side of the river".
That hose is connected to the brake servo unit.
The housing attached to the cylinder head is an engine driven vacuum pump --In old Brit trucking circles, it used to be called an exhauster-they both were the same thing, basically produce a vacuum .
Since you observe the brake fluid mysteriously going down,. the first thoughts are that the master cylinder is leaking from the pushrod end seal into the servo unit and the pump is slurping the fluid out and it is leaking at the slip connector which you have outlined.

Since this is a safety issue --an MOT failure in the making, the first step is to test the master cylinder for internal leakage .
To test it, have the engine running and the vehicle parked. Apply light pressure to the brake pedal and see if it sinks to the floor.
If it does the M/cyl is suspect , possibly & remotely the ABS brick!
Next turn off the engine and pump the brakes. You should feel the pedal tighten up as you se up the stored vacuum and it will feel like you are stepping on a brick. If it still sinks then you have serious brake problem. (hopeful not)
Now with your foot still firmly holding the pedal down start the engine, and the vacuum assist being restored by the pump will make the pedal sink a little under your foot pressure and then stop.
Try that out first.
All the best
Tuercas Viejas
a.k.a the dreaded old cocky MOT inspector of the 1970's who sent many old jalopies (Mexican/.Latino "Carcatchas" to the crusher .)

I have just tried what you suggested, when engine off, I pumped the brake until it when rock solid and didn't move, however, when engine on, pedal does make its way to the floor although slowly. So does this clarify that its the master cylinder leaking into the servo unit? Thanks again

 

[Tuercas viejas]

Thank you for the advice, I will try them all out. Hopefully it is as initially thought with the master cylinder leaking into the servo unit. If this is the case, will I need to replace the servo unit? And can the master cylinder be repaired with a new seal kit or is it just easier to buy a new one? Also the hose, from the servo to the pump, can that be repaired/re-sealed?

My advise is as always install a NEW M/cylinder.
The servo unit is debatable as to the internal state of the original unit once contaminated with brake fluid .
Do you have any vacuum adapters and a gauge to test the vacuum holding within the servo?,
The obvious thought I have is look at the joint where the master cylinder meets the servo. Usually sealed by an "O" ring internal leaking brake fluid might leave a leak trace under the cylinder below the M/Cyl.
In any case the simple test I have outlined previously gives you a quick and fairly accurate state of the hydraulic brake system .
As for the vacuum pipe MB supplies the hose in basic parts so you can replace just the fitting is so desired using a heat gun CAREFULLY!
All the best
Tuercas Viejas
p.s I have a very entertaining story of an insurance sales guy selling liability insurance and his Toyota Camry.
Insisting on a DIY repair of an M/cyl he came a cropper one day shortly thereafter the repair . Luckily he wasn't (stirred Mr Bond) hurt but shaken & he seriously modified the Toyota!!
Then got a "nice" ticket by Denver plod!
TV

 

[Tuercas viejas]

I have just tried what you suggested, when engine off, I pumped the brake until it when rock solid and didn't move, however, when engine on, pedal does make its way to the floor although slowly. So does this clarify that its the master cylinder leaking into the servo unit? Thanks again

Yes it would seem you have an M/Cyl internal leak across the internal seals & check valves , and with it a possible leak into the servo unit.
An MOT failure for sure !
Tuercas viejas

 

[FiveBellies]

Yes it would seem you have an M/Cyl internal leak across the internal seals & check valves , and with it a possible leak into the servo unit.
An MOT failure for sure !
Tuercas viejas

Thank you Tuercas, you have been very helpful. I was planning to do a few odds and ends to my car next week, one of them being the front brake pads as they are low. Turning into more work every day, as alarm siren has also failed this week with batteries leaking etc. Might leave an engine oil change and coolant change for another time Think I have enough to be getting on with now.

Once again thank you.

 

[FiveBellies]

Looks to me like this is one for Grober, he knows stuff, My mate MJ could know something positive they will show up eventually, stay cool. Watch the cricket India could lose!

Thanks Peter

 

[FiveBellies]

Yes it would seem you have an M/Cyl internal leak across the internal seals & check valves , and with it a possible leak into the servo unit.
An MOT failure for sure !
Tuercas viejas

I have removed the master cylinder and servo and this was the cause of the fluid leak at the vacuum pump end, the servo had brake fluid inside. I have replaced both the servo and master cylinder. I now have a problem with a spongy brake pedal, bled the lines from all calipers, 4 times, no air coming out. I forgot to bench bleed the new master cylinder before installing it in the car, so my thinking is there maybe air stuck in the master cylinder, either that or I bought another dodgy master cylinder. Am stuck as to what to do next. I may take the new MC off again and bench bleed and reinstall it or I may try and bleed it on the car, but would I need to jack up the rear of the car to do this? My head hurts

 

[OneForTheRoad]

You've not been to aldi lately have you 5 bellies, pissing up the side of vans ?

 

[FiveBellies]

You've not been to aldi lately have you 5 bellies, pissing up the side of vans ?