Brake bleeding woe on MK4 Golf Tdi

[caduceus]

After changing the clutch and DMF, I bled the clutch this week. Then bled all the brakes with fresh fluid as it hasn't been renewed for a while.
Went to drive it after getting it all back together, and no brake pedal.

Do I need a VAG COM cable to electronically bleed the ABS system? I assume that's where the problem lays....

Any tips/help would be much appreciated.

Thanks
Cad

[Jakg]

You probably need to bleed the master cylinder.

I had the same problem on my girlfriends MK4 Golf (2.0 Petrol). Flushed new fluid through all four calipers, awful pedal, could barely stop.

Googled it and found there are two extra bleed points on the master cylinder. Did them in order and the pedal was better than ever.

[bearman68]

The above post has nailed it. Had terrible trouble with a Jetta once - took ages before I spotted the master cylinder bleed nipples. Took 5 minutes after that. (It's not likely to be the ABS system on this - you don't specifically need to bleed it)

[caduceus]

Ah, thanks chaps. 2 nipples I hear you say? Is there a specific order to do them then? One nearest the bulkhead first or something?

God I love Pistonheads. The help and information on here is invaluable.

Cheers
Cad

[caduceus]

Oh well, scrub that.

Whilst bleeding the second nipple I noticed fluid dripping from the bottom of the brake master cylinder. Thought it was over spill that had trickled down.... Sadly not
Already replaced the clutch & DMF this week, along with the track rod ends and ball joints. Now this.

Wtf next with this car

[bearman68]

caduceus said:

Oh well, scrub that.

Whilst bleeding the second nipple I noticed fluid dripping from the bottom of the brake master cylinder. Thought it was over spill that had trickled down.... Sadly not
Already replaced the clutch & DMF this week, along with the track rod ends and ball joints. Now this.

Wtf next with this car

Electrical issues no doubt. (Sorry was that rhetorical?)

[caduceus]

bearman68 said:

Electrical issues no doubt. (Sorry was that rhetorical?)

Actually, more hydraulic BS.

Turns out it was the master cylinder thankfully that is shot. But, the idiot who installed it tightened up the rear union from the cylinder too tight and has distorted the formed end. It was tight all the way undoing it. Doing it back up will be almost impossible without threading it.
10 day back order across the whole of the UK VW dealer network.

And breathe..

[xjay1337]

It's quite commonn (apparently) on Mk4s you can flip the seals in the master cylinder so I would suggest vacuum bleeding from the calipers rather than pumping the pedal. Saves effort as well

[caduceus]

xjay1337 said:

It's quite commonn (apparently) on Mk4s you can flip the seals in the master cylinder so I would suggest vacuum bleeding from the calipers rather than pumping the pedal. Saves effort as well

Vacuum bleeding? Not heard of that before. Not another bit of kit I have to buy that's going to take up room in my tardis garage...

Surely with a new cylinder it's not going to be a problem now. Eezi bleed should suffice shouldn't it?

[xjay1337]

You can either suck fluid through from the nipple (ohh err matron)

Or you can pressurize the fluid reservoir and open the nipple and fluid will come out.

Either way is better than pumping the pedal.

[shtu]

caduceus said:

Eezi bleed should suffice shouldn't it?

Yep, just don't go mad with the air pressure.

[thebraketester]

Buy a sealey vs820. They work great.

[caduceus]

shtu said:

caduceus said:

Eezi bleed should suffice shouldn't it?

Yep, just don't go mad with the air pressure.

So how much? 10 psi?

[shtu]

http://www.mossmotors.com/graphics/products/PDF/38...

Some people go nuts and push stupid PSI through to make it work faster. Unwise.

[thebraketester]

caduceus said:

shtu said:

caduceus said:

Eezi bleed should suffice shouldn't it?

Yep, just don't go mad with the air pressure.

So how much? 10 psi?

I do mine around 1bar i think

[caduceus]

Ok. I'll try 11 psi first and see if that gets it moving. I don't want to risk blowing another seal. Although it IS new cylinder....

[caduceus]

Well, I put the new brake master cylinder on and a new pipe from the ABS pump to the master (I even syringed new brake fluid into the copper pipe before fitting to pump).
Put it al back together and bled the brakes. NO AIR coming through any of the 4 corners. I then bled the master cylinder and there was a bit of air there. So bled that out.

Went o drive the car, NO BRAKES

Wtf do I have to do with this car. Apart from push it in to the river.

[colin_p]

Looks like you ae going to have to use vcds to bleed the abs pump.

The process is guided on screen with prompts and repeats over and over again. I find x3 cycles is enough.

It involves opening both front caliper bleed nips at the same time, pressing the pedal when prompted and doing up the nips when prompted. I've done it twice in the past and it is quite straight forward.

But you must keep a very close eye on the fluid level as the process goes through it at a rate of knots!

[edit] if you are close, Maidenhead, and have the car up on x4 axle stands with the wheels off, I could help you.

Edited by colin_p on Sunday 19th March 19:15

[caduceus]

Thanks for the info and offer Colin, but I'm not local :|

To purge the ABS correctly, won't I need a VAGCOM cable? Which are like, £800 or something? I do have one of those blue eBay cheap cables and have used it in the past, but ended up needing to borrow the proper VAG cable as the cheap blue one was not up to the job.

Edited by caduceus on Monday 20th March 09:29

[caduceus]

I just read this on a MK4Golf site:

"Master cylinder will produce very high pressures, but nothing to do with the container above it. VW dictates 14-15 psi of pressure in the system when using "ezi bleed" kind of systems otherwise air won't remove completely from the system."

When I bled the brakes with Eezibleed today, I used 8.5 psi from a tyre. The reason for this is because I read on a UKMKIVS thread that no more than 9psi should be used, otherwise the risk of blowing a seal could happen. And I really don't want to replace another master cylinder...

I do love the net for gaining information, but sometimes the conflicting opinions are more more stress than help (speaking of the non Pistonheads threads, not here).