Friday, July 4, 2008

Master Cylinder Replacement and Clutch Hydraulics

AudiWorld Tech Articles: "Master Cylinder Replacement and Clutch HydraulicsMelvin Gale 2007

This article applies to: 2001 TT CQ

Brake fluid is supplied to the master by a hose from the brake reservoir, which the clutch and rakes share. When you press on the clutch pedal, the master cylinder forces some of this fluid out the exit port, through a rubber hose about 2 feet long, ( by way of an aluminum 'frequency modulator' -to reduce vibration, I assume) to the slave cylinder. The slave is located inside the clutch housing. And that forces out the throwout bearing, which is part of the slave cylinder (a very unusual arrangement) that actually presses on multiple steel fingers, which move the clutch pressure plate off the clutch disc. This disconnects engine from transmission so you can shift quietly.

Usual cars have a spring in the master cylinder, so no matter what happens at the clutch and slave cylinder, the pedal comes back up. Then, a pedal-on-the-floor-defect usually means master cylinder failure. In contrast, where pedal feels fine but doesn't operate the clutch usually signals a slave cylinder failure. Of course, leaking fluid either place is almost a guarantee that's where the failure is.

TT master cylinders however do not have a spring, (also very unusual), except for the over center spring pressing on the clutch pedal. So, the only force pushing the pedal back up is the pressure plate itself, pressing on the slave cylinder, pushing the fluid back upstream to the master.

So if a TT clutch pedal goes to the floor, you cannot tell where the defect. This is a problem.

This is the clutch master cylinder."

5 comments:

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'Vorsprung Dirch Technik' [ Advantage Through Technology" - Audi's German Tagline. Audi will import 5000 roadsters into North America for an on-sale date of April 2000. Half of these will be equipped as Quattros, and only 1250 are expected to be the 225-horsepower version. So what the heck does TT stand for anyway? That would be "Tourist Trophy" as in Great Britain's historic racing series of the Isle of Man. TT Now Stands for Terrifically Topless.

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