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#16
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[QUOTE=r.e.wing_fc3s;2413568]to clarify and get back to the original question, im still trying to figure out if people out there have ever had their piston cups torn up while bleeding. this seems to be the case with mine. and if my idea of how it could happen is correct.
I have had that happen on high mileage gas vehicles in the past. I worked in a really bad part of New York City, and the cars I drove into work were usually high mileage cars that nobody would be interested in leaning against, much less steal. I always brought the mechanics of the cars up to snuff, and on two occasions, while doing a brake job, the master cylinder would just crap out. Brakes worked fine prior to me doing the job, but for some unknown reason, the piston seals would just fail. I figured that with all the mileage the cars had, the seals just failed due to old age. Replaced the master cylinders in both cars, bled the system, and everything was fine.
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96 E300d |
#17
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Quote:
The distance the rod can travel can totally be controlled by the person in charge of the nipple bleeder. It is only opened a FRACTION of a second AND a fraction of a TURN.....and closed WHILE a pressurized stream is still shooting out.. or going into the clear tube going to the catch can... Repeat until clear non bubble fluid comes out.....and always start with the brake farthest from the master cylinder AS MEASURED ALONG THE BRAKE LINES... Which varies by manufacturer.
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1980 240d , chain elongation, cam marks reference: http://www.peachparts.com/shopforum/diesel-discussion/10414-help-i-need-check-stretch.html http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html evap fin cleaning: http://www.peachparts.com/shopforum/diesel-discussion/156207-photo-step-step-post-showing-w123-evaporator-removal-1983-240d-1982-300td.html?highlight=evaporator A/C thread http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html |
#18
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I have had this failure a few times, but then I tend to pull vehicles out of fields, get them running, and resell or part. I have started vacuum bleeding brakes when bleeding is needed, but if there's a question I replace the MC. Same with hard lines under the vehicle, wheel cylinders on drums, etc.
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#19
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Vacuum bleeding does not work well on all designs...
Pressure bleeding is closer to regular bleeding in terms of being able to expel junk in the lines and air.
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1980 240d , chain elongation, cam marks reference: http://www.peachparts.com/shopforum/showthread.php?threadid=10414 http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html evap fin cleaning: http://www.peachparts.com/shopforum/diesel-discussion/156207-photo-step-step-post-showing-w123-evaporator-removal-1983-240d-1982-300td.html?highlight=evaporator A/C thread http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html |
#20
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Brake Master Cylinder Test
The second from last post by 4X4 WELDER gives the reason why the seals get torn up |
#21
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yeah i always bleed into a bottle, sometimes i will have the helper just pump without closing the valve to flush the old fluid through. i should have said not to press to hard. i have never had good luck with brake bleeding using the mityvac. the pressure bleeder at my old shop worked great though. is there any way that it could just be the seals on the reservoir? i would think that air would rise and not be drawn into the master if those seals wernt perfect? any thoughts?
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#22
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Quote:
if you have the helper pump the brakes with the bleeder nipple open you are going to draw in air.. The opposite of the reason to bleed the brakes...
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1980 240d , chain elongation, cam marks reference: http://www.peachparts.com/shopforum/showthread.php?threadid=10414 http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html evap fin cleaning: http://www.peachparts.com/shopforum/diesel-discussion/156207-photo-step-step-post-showing-w123-evaporator-removal-1983-240d-1982-300td.html?highlight=evaporator A/C thread http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html |
#23
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Yup, never release the pedal when the valve is open.
If your option is to manually bleed with two people, then it's a pretty simple procedure: With all the bleeders closed, have the helper pump the pedal three or four times, then open the bleeder that's furthest from the MC (Right rear on left hand drive cars). Close the bleeder when the flow stops, have the helper release the pedal and then repeat until only clean fluid comes out, no air. Repeat at the left rear, then the right front, and finally the left front. Make absolutely sure the reservoirs are full during this whole procedure, or you'll be starting over. ABS complicates things, and some manufacturers recommend different procedures, especially on diagonally split systems. If there is a question, consult the Factory Service Manual. |
#24
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A perfect description except for this assumption.. probably caused by you being relatively young... I , being OLD, have encountered left hand drive cars where if you follow the brake lines the longest distance was to the left rear.
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1980 240d , chain elongation, cam marks reference: http://www.peachparts.com/shopforum/showthread.php?threadid=10414 http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html evap fin cleaning: http://www.peachparts.com/shopforum/diesel-discussion/156207-photo-step-step-post-showing-w123-evaporator-removal-1983-240d-1982-300td.html?highlight=evaporator A/C thread http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html |
#25
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Quote:
British cars usually run the brake lines down the right hand side, but even most Japanese cars run them on the driver's side (I have seen mail delivery Subaru Legacys that had the brake lines down the right side). |
#26
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if you bleed into a container with a clear tube going from the nipple down into the fluid theres no way that air can be drawn back into the system. you can watch for bubbles etc. when im flushing the old fluid out before i start the standard bleeding procedure of closed valve-pump-hold this works well to remove the old fluid quickly.
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#27
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Quote:
That is just not true because the viscosity of air is so much less than that of brake fluid... it can be sucked into the system at the threads of the brake bleeding nipple. You may get lucky with tight threads...or dirty threads.... but as a rule to operate by you can not trust that situation. This has been discussed in other threads...
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1980 240d , chain elongation, cam marks reference: http://www.peachparts.com/shopforum/showthread.php?threadid=10414 http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html evap fin cleaning: http://www.peachparts.com/shopforum/diesel-discussion/156207-photo-step-step-post-showing-w123-evaporator-removal-1983-240d-1982-300td.html?highlight=evaporator A/C thread http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html |
#28
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LOL? i see your point however i don't think that the viscosity of air plays a major part here. i have seen professional race teams use speed bleeder bleeding screws. they would be subject to the same problem that you think exists. i.e. when you release the pedal air would be drawn in past the threads. i don't think that pro racers would use something thats going to admit air back into the calipers. and i personally have used them with success though not on this car.
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#29
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Speed bleeders are very different, they seal but have a check valve built in. I almost always vacuum bleed since I am usually working solo, and you see bubbles as long as the bleeder screw is open. Air leaks around the threads.
If you don't want advice don't ask for advice. |
#30
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HUM... Major part ?
ANY air in the brake system is major... If you do a search and read the other posts on this you will see that I am not the only one to have pointed out this possibility in the brake bleeding process. AN interesting structural observation... I have no problems bleeding brakes.... you posted this thread with brake problems..... but want to argue with my description of the obvious potential physics problems of not having the nipple closed upon suction being created by letting the pedal up during that time...
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1980 240d , chain elongation, cam marks reference: http://www.peachparts.com/shopforum/showthread.php?threadid=10414 http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html evap fin cleaning: http://www.peachparts.com/shopforum/diesel-discussion/156207-photo-step-step-post-showing-w123-evaporator-removal-1983-240d-1982-300td.html?highlight=evaporator A/C thread http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html |
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