Hi,

 

I’m out to replace the disc n pads front and rear in our vRS. I’ll also look to do a fluid change while I’m at it. Is there a preferred bleeding sequence for the vRS ?

 

Cheers

 John S

Start with the furthest calliper from the master cylinder, so the LHR.  

I've never really understood why it matters, or if it does. Can anyone explain?

I was told that if you start with the closest and there is air in that part of the system you’ll push it towards the master, but starting farthest away will stop that happening?!

But doesn't the air always get pushed towards any open bleed nipple?

When you press the pedal down it pushes some fluid back along the pipe, as the pedal lifts it draws the fluid (and air) towards the open bleed nipple.... in theory.

That sounds completely opposite to my understanding of how the brake pedal works.

You loose the caliper piston bleeding nut, you push the brake pedal, you hold the pedal pushed, you tighten the nut and then you release the pedal. How any air could get from outside into the system? Any remaining air will be trapped at any cavity it passes; the abs system and the caliper pistons. It can't go backwards at the master cylinder since the system hasn't positive pressure. So, releasing the pedal, the only pressure difference is between the master cylinder and the brake fluid reservoir due to the gravity and the atmospheric pressure leading the fluid from the reservoir to the master cylinder. 

I've always taken the line that by doing it the way mentioned meant that the bulk of the old fluid was removed before the smaller amount in the other associated system pipe, so more a fluid change instruction than a just bleeding air out one.

 

I think that the official VW Group way of changing fluid using a pressurised system method, is written maybe just to reduce time for the workshop operator.

The use of a pressurized system makes the procedure able to be done by one person. That means money... 

Irrespective of whether it matters, the order specified by Skoda (source Fabia 2000 ➤Brake systems - Edition 08.2013)

 for the Fabia is as follows. It does not distinguish between LHD and RHD vehicles though, so either they consider that doesn't matter, or one might assume that it is targeted towards a 'majority' of LHD vehicles and so the lefts and rights should be reversed for RHD. If that reversal is done for RHD, then it would look like a 'furthest from MC first, then progressively closer' approach.

 

(Edit: does the ABS block position maybe define the point relative to which things are furthest? That may stay where it is for LHD or RHD? In which case the below order would apply to all)

 

Bleeding sequence

1. Rear right wheel-brake cylinder/brake caliper

2. Rear left wheel-brake cylinder/brake caliper

3. Front right brake caliper

4. Front left brake caliper

 

 

Edited 22 October, 20196 yr by Wino

The ABS block is always on the left side, hence right rear first I guess.

I honestly didn't see your post before adding my edit sep!

What's your take on whether/why it matters?

 

Edited 22 October, 20196 yr by Wino

1 hour ago, Wino said:

I honestly didn't see your post before adding my edit sep!

What's your take on whether/why it matters?

 

 

Really makes no odds with an ABS system.

 

There are two connections to the ABS module (normally). If there is air in either of those it will be pushed down to the ABS block and then could in theory end up on either side of the diagonal split. If there is air in the ABS block it will come out of whatever circuit it is in anyway. 

 

On a service fluid change is makes no difference at all. (If) there is any air then it will most likely collect at the caliper end anyhow.

 

Pressure bleeders are very inexpensive now and well worth the investment. Does the job properly and far less risk of running low on fluid and injecting air. Also cleaner and easier to operate.

1 hour ago, sepulchrave said:

The ABS block is always on the left side, hence right rear first I guess.

 

It's on the opposite side on a left hand drive vehicle.

^ Ah, there goes that theory...😆

If you aren't introducing any air to the system and you are just changing the fluid, even if it did make a difference in the the order It doesn't apply as there should be no air to bleed out anyway

Interested in this one, as a few years ago ,i made the mistake of having a fast fit place change my rear brake shoes, and I ended up with air in system . Local garage/MOT place ( who advertise as Merc/VAG SPECIALISTS) bled the system ,but I've always felt that there was air left in. As I've mentioned in another post, I've got poor handbrake performance so it's shoe change time, and perhaps time for a fluid change, as I notice fade on long braking runs.

So ,will a presure bleeder ( Gunsen type) push out air from all system ( and ABS) ?

 Bleeding order _ ?? any reason why  i should start at rear, as I've always been told to start at nearest to master cylinder ( this was on older cars with a single circuit) and work back, thus pushing the air to the furthest corners.

The best thing to get the air out of the system is to run the ABS pump with VCDS, having said that, one time I had issues after draining a system and I must have been round the car 5-6 times and the pedal was still crap. I looked in the Haynes manual and it said to bleed the rears in tandem and the fronts in tandem and that did the trick for me as I didn't have VCDS at the time. Its worth a shot if nothing else

How do you bleed brakes in tandem? Do you need one person on each wheel, front or back?

I got a pair of the one man bleeding kits (the pipe with the NRV on the end) and just undid both rear bleed nipples and pumped the pedal a few times, then did the same on the front, then went round and bled individually again.

I mentioned self bleed nipples before. That would have satisfied the problem of tandem bleeding. But Haynes says for mine , it's