Marc's 1990 4.2L V8 Twin Turbo Coupe Quattro

Post by **Marc** » Tue Jul 31, 2007 1:00 pm

Toxcheap wrote:Marc think those four piston calipers require a bigger master?
Bleeders are facing up right

Hmm, I've never heard of anyone else having this problem when putting on bigger calipers? My next step will be to block off various ports on the master to see how that affects the pedal.

yes, bleed screws are facing up :slap:

Lt. Sarge · Post by **Lt. Sarge** » Tue Jul 31, 2007 1:14 pm

I've got 4 piston 996 calipers, and my pedal is plenty stiff. I am running a hydraulic setup though I believe, not vacuum assisted.

Josh · Post by **Josh** » Tue Jul 31, 2007 3:13 pm

adjust the rod on the vacuum booster? Sounds like u might be off a bit when u swapped to vacuum assist?

Post by **Marc** » Tue Jul 31, 2007 3:13 pm

newt wrote:Pressure bled them?

I've had similar bleeding problems on my 90 and had to flow a ton of fluid through i with a proper pressure bleeder to clear it all up.

yes, always pressure bled. I have just discovered that my brake booster does not hold vacuum, tho.. time to add to the order apparently!

Post by **Marc** » Tue Jul 31, 2007 3:14 pm

Josh wrote:adjust the rod on the vacuum booster? Sounds like u might be off a bit when u swapped to vacuum assist?

it puts the pedal as far out as it will go as it is.

black-wolf · Post by **black-wolf** » Tue Jul 31, 2007 4:50 pm

i have seen a bad master do this before. the primary cup blows out and the fluid pushes past to the secondary side.. no leak, but no primary either. if audis are set up the same as I think then your stopping with one fron and the opposite rear. bleeding via pedal will seem to work ok since there is little pressure to push the bad seal to opening. just a thought.

Post by **Marc** » Tue Jul 31, 2007 5:44 pm

black-wolf wrote:i have seen a bad master do this before. the primary cup blows out and the fluid pushes past to the secondary side.. no leak, but no primary either. if audis are set up the same as I think then your stopping with one fron and the opposite rear. bleeding via pedal will seem to work ok since there is little pressure to push the bad seal to opening. just a thought.

ok, so here's a good question, what is the best master cylinder I can get that will bolt to the vacuum resevoir? (eg largest bore)

Toxcheap · Post by **Toxcheap** » Tue Jul 31, 2007 6:23 pm

I believe 5000's and S4/S6 had the best up to the late 90's now with all the new Audi's with massive brakes I'm not sure.

RSCoupe · Post by **RSCoupe** » Tue Jul 31, 2007 6:59 pm

The larger the master cylinder bore, the less feel you will have...

Post by **Marc** » Tue Jul 31, 2007 7:03 pm

RSCoupe wrote:The larger the master cylinder bore, the less feel you will have...

but the more fluid flow per inch of pedal travel, which is what I'm after.

black-wolf · Post by **black-wolf** » Wed Aug 01, 2007 1:08 am

the 5k and 200 avants, and probably the s4 and v8's. the avants use a diff one than the sedans.

Josh · Post by **Josh** » Wed Aug 01, 2007 1:46 pm

your stock coupe quattro is 25mm which is the largest. V8/20020v/s4 have 25mm too, but they're different because they have only two outlets

Post by **Marc** » Thu Aug 02, 2007 7:25 pm

bad master cylinder confirmed. Ordered a new CQ brake master. Car is still driveable, basically only using half the master cylinder.

For ha-ha's today I unhooked the cut valve to let it run straight out the side full time. Holy hell its loud. And I liiiiiiiike it! Not going to leave it that way but I will for the drag strip

Post by **Marc** » Tue Aug 07, 2007 8:09 am

anybody seen this happen to an audi rear subframe on a non-rally car???

Looks like the spot welds busted open and it just started opening like a tin can :-o

I had some new rear tie rods to put in so I welded it shut and painted it up while I was in there, as well as seam welded the other side for good measure...

I need to take the subframe down later anyway once my suspension arrives to do the subframe bushings so I'll powdercoat it at that point..

yikes.

a_CQ · Post by **a_CQ** » Tue Aug 07, 2007 8:18 am

Hmmm, should of welded mine when it was out last year. I'll be watching it.

owdlvr · Post by **owdlvr** » Tue Aug 07, 2007 10:03 am

Seems to be more common the coupes for some reason.

Weird that I've never split one...knocks on desk...

-Dave

Corey · Post by **Corey** » Tue Aug 07, 2007 11:21 am

Very often :tard:

on Torsen/turbo equipped cars. It is to do with the twisting motion, all high bhp ones we do require seam welding to prevent this.

Toxcheap · Post by **Toxcheap** » Tue Aug 07, 2007 12:25 pm

yup that's happened on everyone of my cars, and I've found it even on ones I've bought.

Ronald G Wainwright+ · Tue Aug 07, 2007 2:01 pm

Marc, you got any intercooler's on the car?
I went through a few pages & I couldn't find anything..messy thread to try too find info on..but my minds still boggled over nate's thread :tard:

Derracuda · Post by **Derracuda** » Tue Aug 07, 2007 2:35 pm

yeah... two intercoolers

Ronald G Wainwright+ · Tue Aug 07, 2007 3:00 pm

Yeah I seen them. One front mount & the other is tucked up in the pass side frame rail area.
Thanx Derek :wink:

WAUG0806 · Post by **WAUG0806** » Tue Aug 07, 2007 4:14 pm

I was impressed at how well it handled the armpit hot and humid weather and the autocross paddock here at the OSQ IV GTG...

lots of hot hardware packed under that hood 8)

Toxcheap · Post by **Toxcheap** » Tue Aug 07, 2007 5:16 pm

WAUG0806 wrote:lots of hot hardware packed under that hood 8)

Think he's trying to compensate for other "short" coming? :lol:

Post by **Marc** » Wed Aug 08, 2007 7:18 pm

new mastercylinder, same problem :(

not sure what's going on, only thing I can figure is something wrong with the linkage attached to the vacuum booster, so new vacuum booster is the next step. EG, the rod that runs through the vacuum booster doesn't start pushing on the master cylinder rod until too far down the travel. It isn't the adjustment, its as far out externally as it can go.

I probably should hold off making the car any faster until I can make it stop reasonably well..

Toxcheap · Post by **Toxcheap** » Wed Aug 08, 2007 7:34 pm

bummer!!
Can't say what it could be.... never had problems like this. It must be just you, you couldn't get that cart bled either remember? :wink: