[SOLVED] Brake pedal travel...

Discussion in 'Wheels, Tyres, Brakes & Suspension' started by momomo, Sep 5, 2016.

  1. momomo

    momomo Hardcore MB Enthusiast

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    Apologies in advance for the lenghty post.

    Hi guys, hope someone can point me in the right direction.

    Car is a W212 E350 CDI 2012.

    The pads were due a change and the discs had some life in them but deciced to change everything in one go.

    Alloys needed a refurb so had them sent off. At this point i decided i would also remove the calipers and get them re painted by the alloy refurb place as they also painted calipers. (well known reputable company)

    The calipers were received back with no issues. All seals good. Everything was covered up which needed to be covered before painting. Please note, the calipers were not stripped or taken apart.

    I put everything back together, calipers, pads, discs etc. Discs and pads are genuine parts. I pressure bled the system the text book way- furthest from the master cylinder etc. I used a pressure bleeder, no pedal pumping. (i have changed discs and pads, and bled the brakes too many times to count, so this is not a case of lack of experience).

    I also changed the pads and bled the brakes on this car before without issues using the same method.

    NOW, after completing all the work, the first test drive immediately told me the pedal was not right. There was no biting point and the pedal travels right to bottom before it bites. Not right.

    So bled it one more time. Improved slightly but the same issue remained.

    A mistake i feel i made- i did not plug the brake lines once the calipers were off. The flluid in the system was drained. Excessive air must of got in the system or in the ABS pump. But multiple bleeds should have got this out.

    When pushing the pedal multiple times, the pressure builds but gradually goes and pedal sinks again to the bottom if you stop pumping.

    At this point, i gave the car into Mercedes. They maintain the car yearly and are familiar with the car (just to keep the service history).

    They have bled the system using their official method, machine and run the abs pump while bleeding to ensure all air is out. There are no leaks. They confirm everything is fitted correctly, parts are all correct, servo is ok.

    They are stumped at the moment as am i. They will be getting a 'specialist' technican in tomorrow to bleed the brakes at a much higher pressure using another machine.

    Would anyone have any ideas at all what could be the issue?
     
  2. PobodY

    PobodY Hardcore MB Enthusiast

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    If you're sure it's not air, then a leak somewhere? - I would have thought it would be pretty easy to spot it though; just look for where the brake fluid is dribbling.

    If the pistons and seals in the callipers are all in good condition any chance it's damage to the master cylinder? - I wouldn't normally suspect that on a car of this age, but if you've eliminated everything else it's worth checking.
     
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  3. Will

    Will MB Club Veteran

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    I know you say you/they have checked, but you've definitely got the Left and Right calipers on the correct way round - where abouts are the bleed nipples (?)

    Has to be air in the system?
     
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  4. OP
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    momomo

    momomo Hardcore MB Enthusiast

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    Agreed. I checked everything over myself more than once, in terms of leaks and nothing is visible anywhere.

    Calipers are all very good condition.

    I also can only think of the master cylinder now but at this age it just does not seem likely. Before me only Mercedes ever did the work using good methods that would not damage the cylinder. The car is with them now and they tell me that the cylinder is perfect also after checking everything ok.
     
  5. OP
    OP
    momomo

    momomo Hardcore MB Enthusiast

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    Hi Will, long time, hope you are well?

    Im 100% the calipers are fitted correct. They can only go on one way and are designed to fit only that corner they are suppose to be on. They also have those Mercedes Benz logo plates that pop on the front of the caliper and again this means you cannot get them wrong when fitting. Mercedes also confirm that all the brakes are fitted perfectly and correctly.

    The bleed nipples are located near the top caliper facing the rear of the car always- towards the brake lines on all 4 calipers.

    I thought air too. Can't honestly see it being anything else.

    Hoping they can use a higher pressure bleeding system and get some results later today.

    This is has been one of those issues that drives you mad as its so hard to diagnose and rectify.
     
  6. zipdip

    zipdip Hardcore MB Enthusiast

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    Well it must have taken some time to refurbish the brakes and alloys and you allowed the brake fluid system to be open to the air,I would have thought that the slave or master cylinder seals have dried out and one of them is letting by,what puzzles me is that MB says the master cylinder is ok,they must get the low pedal situation,keep us posted it will be interesting to find out what has caused this.
     
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  7. brucemillar

    brucemillar MB Club Veteran

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    ˆ^ This. I would think a seal has gone/moved in the master.
     
  8. Druk

    Druk Administrator Staff Member

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    I did a refurb job on 212 350 rear calipers recently. Pressure bleed as per instructions was useless (Sealey machine) with no pedal.

    Ended up doing standard 'old fashioned' method with mate pumping pedal and now brakes are fine. No idea why but that's what worked. Brakes are now actually better than when I bought the car although that may be down to getting calipers refurbed. @50.000 miles this surely shouldn't be required but they had internal corrosion. Bigg Red did both for £100 inc.
     
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  9. OP
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    momomo

    momomo Hardcore MB Enthusiast

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    I agree.

    Never had an issue with pressure bleeding my 212 350. Strange. My calipers looked in good condition to be fair but obviously im unable to check the internals.
     
  10. OP
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    momomo

    momomo Hardcore MB Enthusiast

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    Thank you for the advice everyone.

    Update- They bled the system again using a much higher pressure for any stubborn air locks. They say it has improved the pedal but its still not right.

    At this point they informed me they would no longer carry out any more work on the car. In my first post i said genuine pads and discs. This wasnt accurate and i should have been clearer. The pads were purchased from MB- made by ATE. The discs were purchased from Eurocar parts as they were considerably cheaper with a promotion they were running. The discs are ATE also. They are 100% correct replacements for the existing discs. I have double and triple checked part numbers and used the ATE part numbers to match up fitting information from the ATE online catalogue.

    They told me as they cannot find the fault, they refuse to carry out any more fault finding until the car is brought back to MB spec which means they want me to pay for genuine discs to be fitted all around.

    They are adamant the discs are the issue as they arent 'genuine'. They want £700+ to do this.

    Honestly, im disappointed and shocked with this level of service. I know for a fact changing the discs will not fix anything with the way the pedal sinks and bites at the bottom. The symptoms do not match the remedy they are purring forward. So they would like me to pay for new genuine discs and then when the issue remains pay for more parts to change on the car until the fault is fixed.

    With certain issues or hard to diagnose issues, i would not mind doing this, but telling me to change the discs to genuine ones when ATE make the genuine ones for them in the first place is ridiculous.

    As they are unable to find the fault or diagnose further, they automatically point fingers and insist non genuine parts are the issue.

    After doing some more reading i am certain the master cylinder is the issue. I was shying away from this from day one as i just felt that the car was not old enough to have this fail and the time it was left dry was not long enough for any seals to dry/shrivel.

    Also when i asked then how they determined the master cylinder was ok and not the issue, the answer was they plugged the car on the computer and everything is within normal parameters. Surely this will not tell them anything about the cylinder and some knowledge is required to check for leaks in the right places etc. Dont think they ahve checked it properly to be honest.

    I have ruled out the servo- pedal would become hard if this was not working.
    There are no leaks anywhere.
    Everything is fitted correctly.
    Parts are 100% correct.

    This leaves the cylinder and the symptoms of soft pedal, which sinks slowly and has no bite match a failed/failing cylinder.

    I informed them to change this next and not to touch anything else. Would expect better from a dealership.

    Will update as i find out more.
     
    Last edited: Sep 7, 2016
  11. zipdip

    zipdip Hardcore MB Enthusiast

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    This is why so many people are giving MB service departments a miss and using a Indy,not sure I would get MB to change the cylinder,it will cost a lot,but let us know what happens.
     
  12. brucemillar

    brucemillar MB Club Veteran

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    Your car cannot tell the difference between manufacturers of discs ;ˆ)

    If they are the correct spec (and they are) then that is not your issue and MB are trying to pull your pants down.

    You could stick a lump of wood in there and the pedal should still be good.

    Tell them to replace the discs at their cost if they do not fix the issue. That may focus their minds on fixing the fault.

    It has to be a seal or a leak.
     
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  13. Druk

    Druk Administrator Staff Member

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    I take the opposite view to this. Why would you fit non Merc (cheapo) supplied parts and when confronted by a fault, possibly of your own making, expect Merc to find and correct that fault whilst at the same time think it wrong of them to reject the car because of where you bought the parts?
    Think of the implications for them if they had fixed it and then for some reason it had been involved in an accident and a subsequent inquiry had blamed the non OE parts they had worked with.
     
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  14. PobodY

    PobodY Hardcore MB Enthusiast

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    I agree. - MB provided the pads, so although they may not be branded they were obviously happy enough to sell them as equivalent.

    I will concede that if the disc is wrong (for example too thin), then there might be excessive travel. However that normally sorts its self out after a couple of brake applications.

    If they replace all the parts with MB branded components, and that fixes it we'll all eat humble pie (and you'll need to return the existing parts as being unfit for purpose).
     
  15. brucemillar

    brucemillar MB Club Veteran

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    ^ agreed.
     
  16. OP
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    momomo

    momomo Hardcore MB Enthusiast

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    Although i have never had issues with the dealership before, this is the first time they have to fault find for me and i feel they have not been very good at this. My impressions now days is that they just rely on the computers which they plug in and follow what it tells them 99% of the time.

    A indy would not do this. I use Olly and highly recommend indys that are like Ollys, honest, know their craft and have some skill to be called a specialist/mechanic.

    Exactly. I dont think its ok for them even say this to me. Its just that they are a bit stuck as to what the issue is so they have jumped on the non genuine part wagon.

    A sinking pedal like that would not have any relation to genuine or genuine discs. As long as the discs are correct, which they are, they should not be a problem for them.

    They are not cheapo. They are OEM. Since when was fitting OEM parts cheapo? If you could clear that up for me i would be grateful

    And again ill state, they are ATE discs. From Germany. Who also happen make the original discs for MB for my car and seem to make braking components for Porsche, VW, Audi etc etc etc. And they make the pads that i bought from them for my car also.

    ATE make the genuine discs that they are asking to now fit. So essentially, they are asking me for £700+ to fit the same thing and they feel it will solve the issue when they are last thing they should touch. With other certain parts i can understand this view point, but with this issue, no way.

    What difference is that going to make in fixing my problem and safety later on down the road when they are the exact same discs. Oh there is a difference, my discs do not have the 3 pointed star on them. that will surely help me stop alot quicker. Please note i have always bought ALL parts from Mercedes, always genuine and never fit anything aftermarket. This time around, with the discount at Euro, i could get the discs 40% cheaper than Mercedes prices and they are the exact same thing.

    I gave the car in to them to fault find and find the issue. Not find every non genuine part on the car and lay blame on it as they cannot diagnose the issue. They are suppose to be qualified mechanics. So through correct procedures, they can eliminate causes to this issue until they are left with the most obvious problem based on the symptoms. Changing the discs to 'genuine' ones will make no difference and is the last thing they should be looking at. Especially where they concede that everything is fitted perfectly. Have a soft pedal that sinks to the floor has nothing whatsoever with discs being non OEM.

    I want them to find the issue and fix it. Not tell me that as the car non OEM parts which are not even contributing to the current issue as such, need to be changed. They may as well have asked me to change the wipers on the car if they werent genuine, thankfully they are genuine.

    My biggest gripe is that they are suppose to know what they are doing. I know that if i took the car to Olly for example or any good indy, which i would of if not the distance and lack of brakes- he would never say replace the discs for genuine ones- because as a mechanic and someone who works on cars, he knows this would be stupid and not affect the issue. They do not know what they are doing and not once have they tried to use the symptoms to suggest a logical remedy. In this case the master cylinder. I had to suggest this based on the pedal symptoms myself and that there was no improvement after high pressure bleeding.

    I mean no disrespect and do understand your viewpoint however.

    Yes if the discs are wrong, it could be the issue causing my problem. But as i menioned above, i have triple checked the part numbers to be right with ATEs own catalogue and Eurocar parts, i compared the discs to old ones before fitting and they were like for like, apart from having more thickness. When fitting the pads, if the discs were too thin, i would have also noticed as the pads snug to the disc when fitted.

    They tell me that even if they replace the discs to MB ones and the issue remains, i will be responsible for the bill and they will not cover anything. I will gladly eat some humble pie, i just want the issue resolved, but i know the new discs will not fix the issue and instead of looking at other areas, they feel after bleeding twice, they will not look into anything else.

    I should have an update tomorrow. Am looking forward to this.
     
    Last edited: Sep 7, 2016
  17. PobodY

    PobodY Hardcore MB Enthusiast

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    May the force be with you.

    It has occurred to me that if all the components are good, and there are no leaks, could it be as simple as the brake pedal rod is out of adjustment? - Essentially there's too much free play so it's not putting pressure on the master cylinder.

    I've never changed a brake master cylinder, but when I changed the clutch master cylinder on the Nissan I spent a lot of time upside-down in the footwell inching the threaded rod around to remove the free-play and set the clutch pedal height correctly. Until I did that, the first 10cm or so of travel did nothing, and it was all in the remaining travel.

    It's just a thought.
     
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  18. OP
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    momomo

    momomo Hardcore MB Enthusiast

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    They fitted the new cylinder and there is no change according to them. Im taking the car back. I am determined to find the issue and fix it myself now. Im now very sure there is a leak somewhere in the system.

    Have also spoken to Olly to exchange some thoughts and he agrees with me- thinks its ridiculous that the discs are being suggested as the issue. His first change would have the cylinder after the bleeding also- so we are on the same page. Now there are 3 things left- more air in the system which is not coming out or a leak somewhere- will be cheking all calipers and lines everwhere and refitting everything. Lastly the abs pump will be the final suspect- but MB confirm the computer says that is operating perfectly (this they can check with the computer atleast).

    Thank you everyone and Olly for your help and time.

    I will update if anyone is interested.
     
  19. OP
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    momomo

    momomo Hardcore MB Enthusiast

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    I will look into this but i doubt this purely as it was never touched or disturbed at all during the disc/pad/caliper change. Also the pedal doesnt have the play that would be evident if the rod was not in place.

    I will still take a look to cross off the list. Again many thanks for sharing your experience and advice.
     
  20. a111r

    a111r Hardcore MB Enthusiast

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    I had a similar problem with a sinking pedal after bleeding with a traditional tube with a one-way valve.

    I'd done some brake work as the last MOT said the discs were warped. New discs and pads had been incorrectly installed = run-out, caused by hub rust (BTW, the car had done virtually no miles since, otherwise these components would not 'go again'...)

    I cleaned, refitted and bled off (because of the old brake fluid) and the braking effort met the MOT standard but the pedal feel was terrible, sinking.

    Thus I drove it, while I ruminated on all the potential failures...M/C, servo, ABS unit, etc.

    After some bedding in, I bled it again using the same basic method and all was restored to normal.
     
    Last edited: Sep 8, 2016

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