96 A4 Quattro. Was Reading and found some helpful posts about diagnosing brake problems. Pedal goes to the floor. I check all brakes and callipers and found one frozen pin and replaced/fixed. Still no luck.

Ive heard that the next step is to block off the master cylinder and test. Does anyone know the Thread size of the flare nuts on the steel lines going into the Master Cylinder so I can get some brass bolts to block off the Master cylinder to find out whether the cause is in the MC or in the ABS portion??

brakes work but pedal sinks about to the floor and what to get it taken care of before we drive again. Thanks!

 

The large ones are 12mm and the small ones 7/16". Depending on how often the lines were removed, they fittings could be corroded on, watch out if that happens because if you go to the dealership there are no brake lines for our cars in the US or Germany.

 

REALLY!!! WOW. They dont look too bad but Ive always hated messing with them and bleeder valves as if your not careful! Also WOW. standard (7/16) vs metric huh.

Thanks! as My next step was to just go buy a replacement steel brake line and take if off of there! You saved me tons of time.

Now when you say Large ones are you speaking of the rubber lines to the calipers vs the steel lines? as all the steel lines that I saw/recall appear to be the same size.

Thanks!!

 

You can't just go buy replacement. Audi uses a bubble flare. Pep Boys might put a bubble flare on but they will probably want to sell you the tool instead, stealership can do it too.What I meant was the large fittings in the equalizer block. they are the top 2 and the bottom 2. I believe the one that goes from the car to the rubber line is 12mm too but I can't remember right now.

 

Ah...special flare on the lines...nice. Ok...the equilizer block I assume is that milled pc/ABS just after the Master Cylinder......so then really that mean the only 7/16" lines (from your recollection) is from MC to Equilizer. Im hoping its just the Master Cylinder as that by the looks of things looks easier than the ABS system...yikes. We will see......Thanks SO SO much for the help airguard350!!! saved me alot of work/calling.

 

when the pedal went to the floor you could have damaged the seals in the master cylinder by overextending it. that is why people put a 2x4 under the pedal when bleeding the brakes, so that you dont push the pedal too far.

 

Ah.....good point... will have to remember that BUT...it was like that from right when we bought the car a couple of weeks ago so...Plus when bleeding I only press the pedal about 3/4 of the way just for just that reason. Learned the hard way on a vw years ago!

I see they dont sell rebuild kits for the master cylinder huh. You gotta just go new. If im wrong please point me in the right direction as Ive seen no rebuild kits so far.

Thanks!

 

Audi would argue that the reason for the lack of rebuild kits would be- they dont want to leave an important safety system, like the brakes, to any old mechanic who could screw it up, they would prefer to sell you new OEM quality master cylinder.

but the reason is more likely because its easier for them to just replace it, and it makes them more money to do so.

 

You are very correct Ghost.........Do they take the old ones back as cores? Oh well, either way......it sounds like I may be in for a new one. Atleast like I said Id rather have to put in a new MC than that ABS/Equalizer 'THINGY". Thats is the correct Term right....."THINGY"! LOL Cuz I dont know anything about that. Master Cylinder i can do.

Thanks Guys. I will get some brass bolts at lunch and close off the Master Cylinder and see what she does. again I know she still sank with all the Wheels Lines Clamped off........

I come to like having brakes.....they are good!

 

brakes are a good thing. the ABS system isnt as hard as it may look under the hood with all those lines coming out of the block. its pretty much the module (computer) hooked up to a set of valves. when you replace the valves or do work on that part of the system you need to hook up the car to vagcom and run the ABS pump so it gets all the air out of the system. then you can bleed everything like normal.

that being said it doesnt sound like your problem is related to the ABS.