Hi all !
I've changed the brake fluid on my Superb Mk3 few weeks ago. I fumbled a bit, but the maintenance manual found on cardiagn.com helped me a lot!
Requested parts :
- 1,5 to 2l of DOT4 brake fluid. Don't forget to get ESP compliant one.
- Break cleaning spray
- Difficulty level: 2
- Operating time: 1h or may be much more... (see below... )
- Number of operators: 1
- Required tools:
¤ A bleeder kit, including container for used brake fluid.
¤ A syringe (brake fluid resistant)
¤ A wrench of 11
¤ Torque wrench and socket of 11
¤ Jack
¤ Cloths
¤ Multigrip pliers
¤ A small torch.
Possibly 50 cm of aluminum foil + masking tape ... (you will understand below)
Tools:
I've bought the following brake fluid bleeder kit:
It can be found under different names of resellers and on different well known online shopping sites for ~ 55 to 60 €.
A little tip, when making the choice, look at the opinions of buyers, because there are several diameters (even if there is a standard for European vehicles). For the one I chose, there were a few previous buyers who had used it on VAG vehicles. A good guarantee to avoid any bad surprises...
A very simple and useful improvement before starting: make graduations on the used fluid container:
A graduated beaker, an indelible marker and a strip of scotch tape (to mitigate risk of erasing by rubbing (Skoda... Simply clever! )). Well... I may drink half of pint or a soda can from time to time, but assess 20 or 30cl just in a glance, is way over what I'm able to do... or ... I should drink more often ... Well, here at least , one knows how much fluid comes out !
I did the same thing on the bleeder tank, to be able to asses the remaining quantity before I start flushing the last caliper:
It prevents any air from entering the brake fluid tank . Otherwise, you may need to repeat the process on this caliper.
Dealing the syringe, I've bought this one for ~20-25€ (also on a well know shopping website) :
1st Step: Preparation.
First, check that the dip tube in the bleeder tank is correctly set and goes deep enough to the bottom to avoid any risk of defusing the system.
The bleeder tank must then be filled with 1.5 to 2l of brake fluid. If you fill it with only 1.5l, place the tank so that the dip tube is really at the low point (not obvious in the engine bay, that it is perfectly horizontal, especially if you remove the wheels and use a jack)
Keep the new brake fluid cans, once you've poured the brake fluid into the bleeder tank. You'll need them to collect the old brake fluid to bring it to a recycling center.
Once here, start pumping to pressurize the bleeder system (still NOT connected to the brake fluid tank of the car)
I've set the pressure ~ 1.2-1.4 bar. This is more than sufficient, even if the system is can be set up to 4 bar. Anyway, above 1.2 bar, pumping starts getting a little harder.
Wait for ~30s and check there's no leaking. The pressure shall remain steady. If any leak appears, just tighten the bleeder tank cap a little bit (use multigrip pliers if necessary).
When there's no leak anymore, press the pressure relief valve to make the pressure drop down.
Now you can remove the brake fluid tank cap. Remove some brake fluid using the syringe, until the level gets down to the lower part of the yellow strainer.
Then put the adapter cap onto the tank and tighten it firmly (with your hand is enough. And that's a good point, given the poor accessibility ).
You can now connect the hose to the adapter cap:
Pressurize the system again and make sure that there is no leak around the adapter plug on the brake fluid tank. (no small bubble at the bottom of the adapter cap).
2nd Step: Flush the calipers
The bleeding order is the usual one: 1 - Rear Right / 2 - Rear Left / 3 - Front Right / 4 - Front Left.
Considering it was the first time I flushed the brake fluid on a car, I rather removed the wheels for a better accessibility. But it should be feasible to do it without removing the wheels. In this case I would recommend to protect the alloy wheel with aluminium foil stuck with maksing tape (since very easy to remove). This is to avoid accidental damage on the rim paint.
Therefore, without disassembly, we can estimate the required time to 1 hour. If you remove the 4 wheels, it is rather 2 hours.
The bleeder screw is on the upper inner face of the rear calipers. It's now time to remove the protective cap from the bleeder screw. Then install the old brake fluid container, the small chain helps making the container safer (no reversal possible) :
Before starting, spray some brake cleaner on the caliper and on the bleeder screw.
Fit the rubber end of the collecting container securely, then loosen the bleed screw with the 11 mm open end wrench
And... Here we go ... No panic, it flows very slowly ... With 1.2-1.4 bar, it allows you to take time .... At the beginning, the used brake fluid is quite dark, well ... here not that much. I really expected worse. Then, it cleared up progressively until it was really very clear ... So clear that I even said to myself: "crazy, it's even clearer than a Bud light or a Tsingtao!". .. That is to say ! Well, I give it to you, the used fluid wasn't dark as a Guinness either !
Check there's no air bubble in the system all along the bleeding operation.
The recommended volumes for calipers are identical for both manual gearbox and DSG gearbox.
Rear Calipers : 0,3L each
Front Calipers : 0,2L each
In the maintenance manual, you can also find the recommendation to bleed the clutch slave cylinder for manual gearbox only (with 0.15l). But after discussion with a professional, this seems very rarely done and is more risky since it may introduce bubbles into the brake system. So for manual gearbox owners, I let you decide to do it or not.
Note that the maintenance manual does not specify whether these are minimum volumes or whether they already include margins. Even if the Brake fluid was already the right color well before reaching the recommended volume, I had rather to let it flow a little more. Therefore 1.5L is really a minimum quantity to buy!
Once you think this is OK, simply tighten the bleeder screw gently with the 11-wrench. Remove the rubber cap from the bleeder screw and tighten at 10 Nm with the torque wrench.
N.B.: If you haven't removed the wheels, it does not seem easy to access the bleeder screw with a torque wrench, unless you have a socket wrench (fork type)...
Once the first rear caliper has been flushed, old brake fluid color is easy to check as the used container is being filled.
When the 2 rear calipers are flushed, empty the old fluid container into the new brake flluid cans (but empty), which you kept from the beginning. This container has a too small capacity to process the 4 calipers, indeed
For the front axle, the bleed screw is approximately at the same place, on the inner upper face of the caliper:
3rd step: Level adjustment
Once the 4 calipers have been processed, the pressure in the supply tank must be released using the pressure relief valve. You can then disconnect the quick connector from the adapter on the car brake fluid tank.
Warning! Pay attention to possible brake fluid drops, when you remove the whole system. Brake fluid is very corrosive on paintwork!!!
Adjust the brake fluid level in the tank to set it between min. and max. marks. Don't forget to take the discs & brake pads wear into account (as mentioned in the workshop manual)!
This being said, I've checked the discs and pads, they are at least 5mm above the minimum thickness and I'm almost certain that I'll have changed the brake fluid before the brake discs or pads. !
Use a small torch to try seeing the fluid level in the tank. But not that easy...
When done, you can think of "finalization". Replace the brake fluid tank cap.
4th step: retarting
Now everything has been tighten or closed, press the brake pedal several times. It should not go down more than 1/3 of its stroke before you feel resistance. Otherwise, the calipers must be flushed again, because bubbles may remain in the system.
Note : the brake pedal may be hard with a very short stroke (1cm). But when you think you've reached the stroke end, you may notice a curious phenomenon: the brake pedal slowly fade under your foot ! Don't panic, it should go away after a test drive!
A test drive will now allow checking the correct operation of the ABS system and that there is no obvious asymmetry when braking.
Before starting, check that the brakes work from very low speeds. Then brake strongly to test the ABS unit and check it triggers normally.
Normally, if you get here, everything is successful! Well done !
If you want workshop manuals, for maintenance and brakes, you can download them for cardiagn.com
Enjoy !