Hi folks, bit of an odd but scary one.

Just went to start the motor up, 2019 vrs 4x4 tdi.  Brake pedal hit the floor as though it wasn’t there, then on turning ignition on the dashboard warnings come on of low brake fluid etc.  Usual checks round and the reservoir appears to be empty!!  No visible fluid leaks around the outside of the car or engine bay but the carpet under the pedal box is wet with brake fluid 😳😳😳😳

 

Brake pedal just pumps as though there’s nothing there now.  Could it be clutch related?

 

Has anyone had anything like this??  Car drove fine until this, seems like pedal box failure.  Yes I’ve been very lucky but something has gone on here……

Any help appreciated.

I believe the Mk3 brake master cylinder reservoir shares the fluid with the clutch, with the brake fluid being taken from the reservoir lower down than the clutch take-off. It sounds like the master cylinder has failed.  

4 hours ago, mac26 said:

Could it be clutch related?

 

Absolutely not, the clutch would have failed long before the brakes were starved of fluid.

I should have mentioned it’s a dsg, so I’m not sure if that has the same clutch/brake fluid set up.

Looks like the brake master cylinder seals have gone the journey and dumped all of the fluid down the servo, then down the pedal piston.  
 

Quite scary if it had happened with the car on the move, thankfully it didn’t!  

18 minutes ago, mac26 said:

I should have mentioned it’s a dsg, so I’m not sure if that has the same clutch/brake fluid set up.

Obviously DSG doesn't have a driver-operated clutch cylinder.

1 hour ago, mac26 said:

Looks like the brake master cylinder seals have gone the journey and dumped all of the fluid down the servo, then down the pedal piston.  
 

Quite scary if it had happened with the car on the move, thankfully it didn’t!  

I'm sure you would have got a low level warning light.

Does it have a remote reservoir?

 

You might be lucky and find that the feed pipe has come off the master cylinder although it would require an external force and to have been loose so would have been leaking before.

 

Likely the master cylinder seal, be thankful that it occurred at a standstill.

 

I agree that you would have had a low fluid warning when driving before it became critical.

No remote reservoir that I know of but I think I’ve got my answer now.  Looks like it’s actually the front o/s calliper or hose!  
 

It’s been chucking it down all day.  I’ll be thankful if it is.

Wheel off tomorrow when it drys out, there’s fluid all over because of the rain.

Calliper or flex hose failure wouldn't leak brake fluid onto the front carpet - suggest checking the master cylinder too.

Yes, I realise that.  The problem is that it’s been soaking wet all day and it may well be fluid transfer from rain water on the floor too as there’s been that much lost.

 

Wheels off tomorrow will see what’s going on there but yes the master cylinder needs checking too. 

Found the culprit- hose to the front o/s calliper had come loose. 😳

 

Got it sorted with new banjo washers and bleeding the line but it’s getting a full system flush and pressure test.

It is holding fluid and a brake pressure now.

Were you mistaken regarding the brake fluid on the carpet under the pedal box?

 

Have you recently had work done on the steering suspension or brakes of the front O/S? I have never known a correctly tightened banjo fitting come loose in service, could it be a malicious act?

Yes, mistaken by the fluid on the carpet.  That’s been transfer from a wet floor and panic in the moment!  
 

My wife drives the car mainly of late and it was when I got in it that the alarm bells rang so to speak.  I’ve never known a hose union come loose in this way ever.

It did get a cambelt and water pump done but that was back in August from a reputable garage, but then again…..

It does have braided lines on it and steering movement left/right would push the banjo union loose if not fitted hard up to the stop flange face on the calliper.  The N/S left right movement would serve to tighten it if that happened due to its orientation.

 

The banjo in question was well away from the backstop face where it was originally fitted by me and the unscrewing motion would push it towards it.

Malicious act is what I’m thinking as it’s looking like all of the engine undershield screws have been swapped out for old rotten ones.  The ones on it were in very good condition for it’s age.

 

Something very similar just happened to my Scout. It has been parked up for 2 months. A lot of travel in the pedal when I went to start it. Once engine running the pedal went to the floor! "Brake Fluid Reservoir" caution popped up. Indeed it looks empty. No obvious fluid seen on the floor. I dare not drive it, so very expensive RoboLift recovery awaited from basement of a multi-story carpark.

Any ideas what is wrong? If this is master cylinder seal failure, where has all the fluid gone? Why would there be such a catastrophic failure after being parked up for 2 months? Brake fluid flush last done 5 months ago.

Chances are it was leaking slightly somewhere and over 2 months of say a drip an hour would empty reservoir.

I woud refill and bleed system then check for leaks. On my old octavia the clutch master failed but all the fluid ended up on the engine undertray. It was only when it got winched onto recovery truck it leaked out. On mine the brake/clutch reservoir is shared but think the brake fluid outlet is lower than the clutch so clutch fails first. If yours is empty then check the connection from reservoir to the brake master cylinder. They can leak at the reservoir.

51 minutes ago, Piston_Broke said:

Something very similar just happened to my Scout. It has been parked up for 2 months. A lot of travel in the pedal when I went to start it. Once engine running the pedal went to the floor! "Brake Fluid Reservoir" caution popped up. Indeed it looks empty. No obvious fluid seen on the floor. I dare not drive it, so very expensive RoboLift recovery awaited from basement of a multi-story carpark.

Any ideas what is wrong? If this is master cylinder seal failure, where has all the fluid gone? Why would there be such a catastrophic failure after being parked up for 2 months? Brake fluid flush last done 5 months ago.

Manual or auto?

5 minutes ago, ords said:

Manual or auto?

It's an auto. Apologies for not specifying.

14 hours ago, Piston_Broke said:

It's an auto. Apologies for not specifying.

Ok, then it's purely a problem with the braking system

Off-side rear caliper was found leaking and replaced.

New rear discs and pads were installed in October. I wonder if the seals were stressed when presumably the pistons were retracted?