I need the Locostbuilders' collective brain power to help me with this one:

My TT has been sitting for a few weeks. I just got some winter wheels and tyres for it, put them on and took it for a test spin.

Came up to the first junction and the brake pedal went practically to the floor. Very long travel, brakes engaging at the end. Will still lock wheels up into ABS but this is on relatively slippery roads.


First thought.. air in the fluid. Pump the pedal up - no joy, the pedal doesn't pump up.

Then thought.. fluid escaped somewhere - checked cylinder, it's on Max, no movement at all.

Servo broken? Then it would've either been a really stiff pedal, and in any case shouldn't affect pedal TRAVEL length.


So, before I start crawling under the car in the snow, could anyone offer up any suggestions?

Keep in mind this happened after about a month's worth of the car standing, and isn't something that gradually got worse, it just happened. And since then hasn't deteriorated or improved (only drove it for a couple of miles).


Thanks,

Pavs

maybe a knackered slave?

Possibly the ABS pump, massive weak point on modern VW/Audi's. The problem is they dont show up a fault code untill on last legs.

But what's happening to all the fluid through such long pedal travel? It must be going somewhere. Knackered slave might explain it but I would've thought the pedal would just stay down and not return?

Thanks,

abs pump sticking valves . light tap with hammer on pump assy and poss change brake fluid (Flush out) bleed brakes with engine running hope that works...

As there is no apparent fluid loss the candiates are either air in the system or the master cylinder fluid passing fluid back to the resevoir.

My money is on the master cylinder, first try putting pressure on the pedal by pushing the pedal very gently and really s-l-o-w-l-y. If the pedal sinks very slowly while the fluid level rises slightly then the recuperating seal or seals in the master cylinder is/are shot.

The other test for the master cylinder is to disconnect the pipes and blank the holes off with bleed niplpes after a very quick bleed the pedal should be rock solid -- remember to re-connect the pipes after this test.

Might be a stab in the dark have you checked that nothing has happened to the connection between the master cylinder and the brake pedal itself, theres usually a pivot/clevis pin, if your some reason its snapped/come loose then the connection could be moving up the pedal when pressed and not pushing against the master cylinder correctly, if that makes sense.