[V6-12v] Rear Caliper work

[Clive Young]

Hi Guys

 For those of you who have been following my project audi, I have a new installment.This one was an excellent lesson in patience determination and pig headedness. 
    With my C.P.S. behind me and my electric antenna torn out waiting for a new one I moved on to the rear brakes. I had noticed rust on the outside of both rear disks which is a huge no no given this is a daily driver and new I was in for an interesting time. 
    I removed the wheels with the car on Jack stands for the winter and went to work. This car has 240,000km but not sure if the brakes were original ( yet ) . To take the disk off you need to remove the caliper and what I will call the "slider housing". I just made that up but it is the part fastened to the wheel hub that the calpiper "floats on" to allow the pads to work from both sides. The principle is pretty standard. single caliper piston pushes one side of the disk and pulls in the other pad on the slider. I removed my two 13mm bolts to remove the caliper from the housing and that is pretty much where the fun ended. Audi uses to slider pins that slide into the slider housing bolted to the caliper to allow both pads to compress. the holes in the housing are about 3 inches deep and the slider pins are well greased to slide in the hole ( all right minds out of the gutter please ) . There is one at the top of the caliper and one at the bottom. There is a smal rubber colapsable sleeve that covers the pin and hole so no dirt or contamination gets into the grease. North american cars use an open system which is exposed to enviroment but is easy to service (good and bad I guess ).
    On my car the lower slider was COMPLETELY seized due to lack of routine maintance. One inner pad was so badly worn the upper part of the pad was worn through the pad and the metal backing was worn away and the lower part had about .5 inch of pad left. If you can imagine I had a big triangle for a brakepad. Needless to say the rotor is ruined also.... but wait theres more .... 

after taking the 13mm bolts off ( remember they fasten the slider pin to the caliper ) the pin should start to turn because it is not threaded, merely a pin. There is actually  
about a 15mm nut shape on the end of the pin to grab a hold of where it meets the caliper so you can take the 13mm bolt out of the end. the upper ones strted to turn the whole pin as expected so I grabbed the end of the pin , took the bolt out and pulled the pin no probs. The lowers as I said were both seized into the floater housing. the 13mm bolts flew right out without the pin moving so I new I was in trouble. sure enough the two lowers were tight as hell. This is where I should have stopped. On one side I tried to work it loose as it was tight as hell but you guessed it , I snapped off the pin inside the housing. I left it on the car as I figured the two 17mm bolts holding this in place would give me leverage. It did, enough to snap it off. 
    On the other side I had the same problem . I mean it was TIGHT. On this one I toook the two 17mm bolts off and placed the housing on my work bench. Put some liquid wrench on the housing where the pin went in and went to bed. Next moning it was gone , put some more in, etc, later that evening i put the housing in my workmate and while working it back and forth ( about an eighth of a turn without jamming ) had my trusty helper spray in more liquid wrench , lots of patienece and i could turn it more and more. I actually used vice grips ( yes I hate those things too ) but remember you are trying to work it out , not in, so you have to gently pull as you are turning back and forth. Sure enough the liquid wrench worked its way in and out came the pin . Would you believe i just wiped the pin off and it fell in all on its own it was so loose ? that liquid wrench is amazing. 
    Now the tough one. I figured the other housing was scap since I busted a rusted in pin of in there so I had nothing to lose. I drilled a 1/16th hole right through the pin ( about 2 inches ) with a titanium bit . I had no idea why, I was just making it up as I went along. Then I took a bit bigger one and a bit bigger one. I was not lined up in the middle or perfectly staraight but what did I have to lose?. eventually I ended up with drilled out partial pin in the housing. One of my drill bits even went right through the side of the housing at the very bottom but this was a risk I new I was taking. Eventually I started picking away at the edges with a small srew driver thinking this was now a useless quest as it was really hard. I used a hammer and the small screw driver to nock a piece out and the whole pin moved further in .... it was now loose ! ( relatively speaking ) . So I sprayed on my trusty liquid wrench whil I ran down to Crappy Tire to get a broken stud puller. I never considered it before because a 15mm wrench couldn't move it rememeber ? I put in the stud extracter #4 ( for a ,25inch whole  ) started to turn slowly and prayed ( remember it is WAY in there now ) . I felt it bight and was not sure if I was biting the walls on the hole or the pin. I backed it off and put the extractor in the other hole and it touched nothing , just stopped at the mouth of the whole as it was too wide. I new then I had the perfect tool as it would only bite the pin , not the hole. So I put it back and turned again. I heard a sickening snap and pulled on the extractor expecting half an extractor to come out , but out came my extractor and what could very loosly be termed "pin remnants" a slug of drilled out twisted up bashed up ground out metal. 
    So the housing I have is usable, I do have that small hole that was way bellow the bottom section of the pin. I will patch that with some liquid metal to stop elemants getting in but who cares anyway... I beat that thing.

In conclusion it is easy to summarize that the lower pin gets all the salt, water, and crud thrown up by the back wheel and the pathetic rubber seal keeps none of that out so this is bound to happen to any car. Regular maintanance to the rear brakes can save many of the headaches I went through. Just service those sliders ! If you see rust forming on the outside of the disk, you may already be too late. 
    Incidentally someone was selling a kit which included 4 new rubber boots slider grease and 4 new 13mm bolts on EBAY for only $12.00 It wasn't worth it for me with shipping and dutied converted to Canadain but I would suggest grabbing them if you are going to do your brakes. Especially if your rubbers are toast. 

In addition of course I had to get the rotors off. Audi Made a huge mistake in the design of their hub. It fits exactly into the top hat of the rotor. no room to spare, So of course when taking it back off 8 years later you have all the rust on the inside of the top hat jamming it. Tip: before even trying to pull the rotor off, reach around and scrape out as much as you can with a screw driver, then after whacking the rotor just work it off slowly ...  and yes, use lots of liquid wrench .......
    
    So that is where I am at so far ... and I haven't even looked at the calipers yet ,, hope they aren't seized too..... :-)

sorry if I used up too much bandwidth ...

Clive Young 
95 90S FWD 5SPD