Sudden brake hydraulic fluid leak 1999 A6 1,8T

1999 A6 1,8T
Hi folks. Sudden onset of leak of hydraulic fluid at the union of hydraulic hose to rear calliper. As light was fading and working conditions were not great, I
only managed a brief inspection. The connecting bolt was tight. However, I removed it & had a quick look around. My question is whether there are meant to be any sealing washers on the mating surfaces? (Non banjo shape, but banjo type connection) I suspect not, as the block on the end of the hose seems to be machined flat but leaving a bit of a spigot around the bolt hole. Does this spigot perform as if a sealing washer? The surface of this spigot seemed somewhat pitted, which surprised me. Checked everything was clean, reassembled and leak still apparent. The fluid seems to seep under the head of the fixing bolt. The fluid loss seems to be far more than I would have expected, Brake pedal will reach floor without engine power assistance in about 10 seconds.
If no washers are employed I guess I'm looking to replace the rear hose assy. ? Not sure how the flexible hose fixes onto the actual brake pipe? Anybody out there replaced rear calliper, or hose/pipe?
Ian
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Ian, I've never worked on an A6, but chances are the mating surfaces are in the end of the fitting, like a flare with a nearly matching bump in the socket of the cast brake caliper. Usually such a leak does not appear out of the blue, but following servicing in that area - like the replacement of a rotor/pads or wheel bearing. Or, as in the case of my 5ktq's clutch master cylinder, when the fitting is cross-threaded into the cast hole, and the edge of the flare damages the seating bump at the bottom of the hole (local dealer service did that - guess how happy I was) It is possible (although I have yet to see it) that the mating surface could be galled and seal poorly, or the fitting itself could be cracked in the threads, making it look as though the leak is coming through the flare and up between the threads. If it's a cracked fitting, be careful as the more you torque it, the more the crack will open up and if the fitting shears off in the caliper, you'll have to find a place to get a rebuild. Cheers! Steve Sears 1987 Audi 5kTQ 1980 Audi 5k 1962 and '64 Auto Union DKW Junior deLuxes (SPAM Blocker NOTE: Remove SHOES to reply)

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A leak from the caliper P/B lever seal will run down around the brake hose fitting and appear on casual inspection to be a leaking hose/fitting. Careful inspection will confirm. JR
Ian Gaskell wrote:

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ETKA doesn't show any washers, but the pipe to the rear calipers is an assemply of rigid pipe, flexible pip, banjo and bolt all as a single part - 8E0 611 763 K for the LHS, and 8E0 611 764 K for the right hand side.
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Peter Bell (Note Spamtrap - To reply, replace 'invalid' with 'bellfamily')

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Hi Ian, first time I have replied to one of these posts but I have had the exact same problem. My 1998 A6 Avant dumped all it's fluid overnight, quite scary to discover it the following morning!
Anyway, being a cheapskate I trawled round the usual Andrew Page, German Swedish etc to no avail. Had to bite the bullet and visit Audi main dealer - Result! assembly is around 13 each and comprises solid brake line about 300mm fixed to flexy which has a captive banjo type bolt and TWO washers, one front one back. I replaced left and right as I had heard at last MOT that it is a common problem, the pipes that cam off were weird as left had no washers and the right just one! It was repaired for the same problem last year so the mechanic could have bodged the damm thing but be assured, the new ones have two washers.
Furthermore the official brake fluid was cheaper than at Halfords!! Now if I could just fix the ABS light........
Paul

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Commonest is dead brakelights followed by dead wheel sensors. You should get a visible signal on a multimeter from each wheel sensor when unplugged and spun by hand.
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Skipweasel
Si hoc legere scis nimium eruditionis habes.
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no errors showing on your diagnostic too? thre ecu should have recorded somthing for to to find,
Steve.
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Indeed, it was the sudden onset of the problem that amazed me. I can only believe it was the result of corrosion/ pitting of the surface that mates with the fixing bolt. I suppose it's analagous to a dam bursting. Totally intact one minute, but as soon as its breached, the initial flow erodes around it and rapidly escalates to a flood,

I ordered the brake hose today. I will advise if it comes with any sealing washers. My only other thought was maybe to try to improve the surface finish of the "banjo" end of the flexi-hose eg by honing with a sharpening stone, but really dont want to take any risks with a safety item such as this.

Good luck with your ABS problem. You may be interested in a brake related problem my brother had on a Rover 620 diesel. Symptom was an almost total lack of power when he switched the car lights on. Traced it to be an internal fault inside the rear light/brake light bulb. The two circuits became linked inside the bulb. Car lights on put 12 volts onto the brake circuit. ECU thought the driver was braking and cut back power. Presumably a fuel saving strategy. Should probably need brakes on PLUS throttle in OFF position to do it "correctly"
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