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Vito 112 Cdi front brakes
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vitoguy
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Mar 30, 2016, 11:38 AM
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Vito 112 Cdi front brakes
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2002 Mercedes Vito 112 Cdi 120K miles - front brakes seizing partially on and overheating to the point of that smell after 5 minute test drive at low speed.
Checked pads and found them 60% worn but not to the point of the warning light wires being in contact with the discs (rotors).
Could not compress the calliper pistons back into their bores even with the correct tool so fitted 2 exchange callipers and new pads. She now moves off smoothly and brake response is smooth, with no drag but after half a mile or so drag and heating becomes evident as before...
Any help greatly appreciated.....
(This post was edited by vitoguy on Mar 30, 2016, 11:50 AM)
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Hammer Time
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Mar 30, 2016, 4:12 PM
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Re: Vito 112 Cdi front brakes
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First make sure no one has contaminated the fluid in the master with anything beside brake fluid.
If that hasn't happened, replace both rubber flex hoses.
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vitoguy
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Mar 31, 2016, 12:34 AM
Post #3 of 32
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Re: Vito 112 Cdi front brakes
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Thanks for your input Hammer. Yes, only new, clean DOT 4 in the Master. Both front flexi's replaced within last 18 months. There was a single, heavy brake application shortly before this fault commenced. Only the front brakes are seizing. They have new callipers/pads and when rotors tested with an IR thermometer, the seizing is equal on both sides. Are there any tests I can run on the Master Cyl'?
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Hammer Time
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Mar 31, 2016, 1:57 AM
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Re: Vito 112 Cdi front brakes
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The next time they get bound up get the front wheels off the ground and crack the lines at the master and see if that releases them.
If not, them move to the ABS unit and try the same thing there with the output lines.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Tom Greenleaf
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Mar 31, 2016, 3:16 AM
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Re: Vito 112 Cdi front brakes
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Quote">>There was a single, heavy brake application shortly before this fault commenced.<<"
There's a strong clue in that comment.
Question is - what can make BOTH front brakes stay applying (they do just from heat + expanding brake fluid that should return) at the same amount?
Master cylinder OR how it's mounted? I've only even heard of this once in decades on end but possible to bend booster or how it mounts for improper pushrod to master free-play 'lash' area almost always with opposite problems - brakes travel too far before applying but a real slim chance if hard enough it bent out and back in such that it's slightly too much preventing fluid return as it would if you just touched the brake pedal a little and held it there.
Hammer Time suggested cracking open lines as I would too now. Isolating whether at ABS or master will take some attempts to see it not release at each till you can isolate which as I can't believe both or all of the above.
Try all. Have a helper press brake pedal hard and see if there's unusual motion at the master cylinder just to see if anything wrong about that?
T
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vitoguy
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Mar 31, 2016, 4:32 AM
Post #6 of 32
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Re: Vito 112 Cdi front brakes
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Thanks for input Tom. So you're saying there should be some end float or "lash" between the linkage and the master cylinder push rod when pedal not pressed. I'll check all this now. What would you "guesstimate" as minimum free play?
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vitoguy
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Mar 31, 2016, 4:34 AM
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Re: Vito 112 Cdi front brakes
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Should have added : If this were the cause, would you not expect it affect all 4 brakes?
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Tom Greenleaf
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Mar 31, 2016, 4:59 AM
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Re: Vito 112 Cdi front brakes
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Correct > There HAS to be some 'lash' or measured "free-play" such that master cylinder is truly OFF or untouched so that fluid when you release a brake naturally returns - any hydraulic set up, make, model.
This once was an adjustment you would make and can't think of a single vehicle that you would adjust anymore just the natural length of pushrods and the drilled hole of the back of a master cylinder.
This is dang rare but you mentioned a very hard stop so it came to mind as this type of problem is a REAL hair puller since right away for a 2 minute test drive you might not notice anything at all wrong such that a real tech would declare it fine without knowing what you've posted already. Temp measurement is a "10" that it's equal to both front wheels! I was going to suggest measuring exact wear of all brake pads (old ones) to see if they were the same but that really hit me as good info that a problem is just what we know - fluid can't return and it has happened to me with a defective master cylinder with the centering hole was just a mm or 2 off not drilled in far enough.
That car behaved fine for a mile or two. Brakes would self apply the hotter they got even when on purpose I drove it using parking brake only engine heat, heated brake fluid, which expanded and brakes applied themselves to the point of wheels too hot to touch if you let it.
My wonder in that this is rare is if you can see the master move either by the booster or even firewall metal if pushed hard enough has been reported (other make car) to bend which is a stretching of metal to a new shape the might return farther back towards rear of car. Some flex is normal on many but not if it could bend.
I don't want to send you off on a goose chase as this would show up with brake fluid spurting out more than usual proving it can't return.
Now since there was no mention of a new master or booster and pretty much ruled out contamination with an oil added which would be a whole nightmare then I can't rule this out and in mega years this was ONE wheel if a hose not two equally which is the oddity of it to me so has to be one thing in common to both brakes now with new calipers and pads.
Benzos in particular (not a specialty car for me) is duly noted to be quite strong IMO for this stuff so less likely but never say never. This is possibly very hard to nail down for sure and brakes are just too important to not find out why and really fix it,
T
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Tom Greenleaf
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Mar 31, 2016, 5:04 AM
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Re: Vito 112 Cdi front brakes
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Just saw your additional post: It should effect all four but engine heat would effect fronts first! Good thinking on your part. If driven long enough probably would effect all four but by then wheels would be on fire!
T
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vitoguy
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Apr 1, 2016, 9:20 AM
Post #10 of 32
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Re: Vito 112 Cdi front brakes
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Hello Tom, Just been out for local run and it took longer than before for the heat/seizing to occur. Not familiar with your "IMO" acronym?
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Tom Greenleaf
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Apr 1, 2016, 9:25 AM
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Re: Vito 112 Cdi front brakes
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Sorry - I'll avoid them.
IMO = In My Opinion,
Tom
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vitoguy
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Apr 1, 2016, 3:47 PM
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Re: Vito 112 Cdi front brakes
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Don't apologise! I'm taking her round the block tomorrow on hand brake to see if fronts heat up without using footbrake. I appreciate your help!
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Tom Greenleaf
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Apr 1, 2016, 4:10 PM
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Re: Vito 112 Cdi front brakes
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Yes - that's one test holding release of a "parking brake" - "emergency brake" - "hand brake" released just if you can where you are driving.
Vito - These are ideas and Hammer Time already mentioned what meant to me opening brake lines when wheels are holding braking force and if that releases the issue you are narrowing down right where the problem is. It's up to you to try what is suggested and report the results.
Keep in mind using a web forum such as this doesn't replace it being totally checked out by a professional but does give you here 100s of years of experience including an odd issue I mentioned that is rare - very rare.
You are looking for help with a fussy issue in my opinion that would easily be missed by a shop, tech unless witnessed and the time to do it and test out. Many aren't thrilled at stuff that's working right in front of them but does something like this but may seem fine in a quick check.
Good luck. If you or we can nail it down we'll go for the permanent fix,
Tom
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vitoguy
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Apr 1, 2016, 11:27 PM
Post #14 of 32
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Re: Vito 112 Cdi front brakes
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Hello Tom, Took her round the block at dawn a few times without touching footbrake and no sensation of seizing. In neutral she coasts to a stop smoothly with no braking effect and rolls away as soon as drive selected. However, when later parked I felt all alloy wheels and passenger side front was noticeably warm but nothing like as warm as in earlier tests. Remaining 3 wheels were completely cool. In earlier tests as Hammer had suggested, cracking the master cyl' front output pipe did free up the driver's side front. Could this be to do with what I think in earlier days used to be known as a "diagonal split" system although that may have been long superseded? I'm away for a few days but will be back on the case next Tuesday if you can offer any further advice.
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Tom Greenleaf
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Apr 2, 2016, 3:24 AM
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Re: Vito 112 Cdi front brakes
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Quote ">>cracking the master cyl' front output pipe did free up the driver's side front.<<"
OK - That's key info that master cylinder isn't getting return fluid properly and blaming the master for now or somehow not in precise right spot as mounted. I don't know unless visually distorted just how you would measure that. I might try loosing the master from how it's mounted fast while one wheel sticky to see it that can release wheel.
I don't know if this car does the "diagonal split" which I take as the hydraulics are separated by front right to left rear and front left to right rear instead of more common fronts split from rear in the even of a total hydraulic failure you don't lose 100% of braking idea. If you can find a "bleeding brakes in order for the exact car do so." I would be on the same chase not sure if all of same model did or didn't. That will matter most only for bleeding purposes but helps nail this down too.
Back to just front left wheel now warm and all other NOT! Fronts do more work and it's less distance of line could explain why it would heat up a front faster. By the time it's heating the wheels by touch it's substantial heat by the way as it has to travel thru rotors, then on to center of rotor which is slow then on to wheel being cooled as designed by rotor as well. I'm pretty sure heat will actually follow gravity and respond to centrifugal force like spinning something hot heat would be altered the way it travels? Wow, I don't know that from any tests just in general on that but would think possible - let's not get too far into that as a science of heat transfer all of which I am strong in but on items that are NOT moving like this.
Just some notes while my head explodes: This is going to require you to have ability to test and do thing FAST including hoisting all four wheels such that you can spin them after being driven for tests that they each can be turned with equal force per axle at least and in my opinion brakes really off a wheel on but off ground will coast freely on wheels not driving the vehicle and just easy on ones that do but might not coast.
You said a few days off so time to think. I'm now thinking master cylinder alone for the moment and really hope brake fluid contamination by an OIL like product isn't part of this - you said not possible and have to trust you on that.
Hey - when fluid is contaminated many times if so it would be someone has put power steering fluid (an oil) or other in the fill reservoir which should float on the real brake fluid until brakes applied or there long enough to mix in and on thru parts. This would highly likely swell the rubber of the cap where you add brake fluid! Do look for that. I do NOT mean seeing it bellow rather swollen and softer or even not fit properly in cap. Plain water products wouldn't do that to rubber such as antifreeze and other or plain moisture. Wow - also know brake fluid thru rating DOT 4 is water absorbing and will mix and wash off with water - DOT 5 I'm told doesn't absorb moisture. The word for that is hygroscopic property of a fluid, oil or whatever. The reasons vary but brake fluid with moisture instantly ruins the boiling point is the real and first problem.
OK - some time now to think of any ways to nail this down as quickly as possible for sure,
Tom
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vitoguy
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Apr 2, 2016, 3:57 AM
Post #16 of 32
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Re: Vito 112 Cdi front brakes
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Thanks Tom, No contamination for sure, nobody else has had access since vehicle new and only clean DOT 4 used by me. I'll be back on the case next week and will also check the run out of the rotors with a dial gauge (not used for years but will search it out). Master reservoir cap is made from same semi opaque plastic as the reservoir itself and does not have any rubber washers, just a tapered seal.
Regards, Martin
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Tom Greenleaf
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Apr 2, 2016, 4:30 AM
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Re: Vito 112 Cdi front brakes
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Excellent if we can rule out contamination. Let's just forget that.
OK - Know that this thread will probably go on to page 2 so look for the "view all" sign if you are reading then can scroll thru the whole thing. I simply can't be too concise on something this critical to find and fix. I'll remove my sign off flag and note to shorten my posts on this thread as well.
Note on reservoir cap: Plastic is what you see - there's rubber inside that hidden - has to be. Don't worry about it but know DOT 4 will absorb moisture OUT of the air so it has to be sealed air tight yet allow no pressure to build at cap nor vacuum so a bellows of some sort is universally used.
Was and still thinking on how to heat brake parts fast and not too hot with what without using brakes at all. In a snag (in my own mind) with what would do without damage and nothing yet. Hair dryer too slow, heat gun too risky or even propane torch too risky. Forget it, I was thinking of how I'd attack this sucker!
Hang in there Martin - we'll solve this somehow, T
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vitoguy
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Apr 7, 2016, 2:16 PM
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Re: Vito 112 Cdi front brakes
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Took her on the same local run again only this time with both the ABS fuses out, both the control unit and the solenoid unit. Progressive seizure and heating same as before. Help!
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Hammer Time
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Apr 7, 2016, 3:15 PM
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Re: Vito 112 Cdi front brakes
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Look, I told you how to isolate this problem 14 posts ago.
You're just running in circles here.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Tom Greenleaf
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Apr 7, 2016, 8:27 PM
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Re: Vito 112 Cdi front brakes
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Re-Read all that Vito. ABS default isn't it as that ABS OFF not empowered - not yet for that IMO at all. Where does it lock pressure by cracking open lines is first, Tom
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vitoguy
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Apr 8, 2016, 2:16 AM
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Re: Vito 112 Cdi front brakes
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Thanks for further input Hammer. Repeated test and hot, partially seized fronts are immediately released by cracking both master cylinder outlet joints. So you're saying replace both front flexi hoses even though one is under 2 years old and the other under 6 months old. Neither of them show any signs of cracks on outside and no twisting or distortion on installation?
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Tom Greenleaf
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Apr 8, 2016, 2:32 AM
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Re: Vito 112 Cdi front brakes
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OK - Stuck pressure at master but now crack lines at hoses could tell if one or both there. Eliminate what isn't wrong.
I went off on what COULD be a tricky something and still might but AFTER concluding it's not elsewhere.
Hoses: Could both be messed up? Yes. Some could have been left hanging while working calipers off held by hose which isn't good for them at all. Some people pinch them for checks - I will not. Too delicate inside + unseen for that. Outside isn't holding the pressure - inside is different protected by outside of flex hose, T
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Hammer Time
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Apr 8, 2016, 8:23 AM
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Re: Vito 112 Cdi front brakes
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Yep, what you just proved is that it was the master holding it back.
Now for the next test, get them holding again and loosen the bolts that hold the master on and then pull it away about a quarter inch and see if that releases them.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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vitoguy
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Apr 8, 2016, 10:53 AM
Post #24 of 32
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Re: Vito 112 Cdi front brakes
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Done as you suggest Hammer. Pulling the master away from the booster does nothing to free them up.
Trying to follow your logic here, am I shortening the effective length of the master's push rod, losing the vacuum or both
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Hammer Time
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Apr 8, 2016, 10:55 AM
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Re: Vito 112 Cdi front brakes
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Don't touch it. you just proved that wasn't the problem so it looks like a bad master.
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