Bleeding brakes but pedal still hopeless?

[Lotuschris]

Hello Everyone,

Sorry for my first post to be one about a problem...

I am struggling like crazy to bleed the brakes on my Golf GTI MK4 (T plate manual) and get a firm pedal.  I had to replace a rear brake hose because it had done the usual thing of having the washer corrode to the caliper and then leak horrifically at the union.  I have therefore:

1)  Fitted a new rear brake hose.
2)  Bled the entire brake system for the complete car (with a pressure bleeder) in the correct sequence and including the two nipples on the master cylinder.  No air or bubbles present anywere.
3)  Checked for perished or "bulging" hoses, and there aren't any, nor any leaks of any kind anywhere.
4)  The pedal is hard with the engine off, but with the engine running (and therefore servo operating) the pedal becomes very spongy and the brakes are very poor (not safe to drive). 
5)  With the engine running and the pedal being operated the red "brake fluid warning light" comes up after a few pumps, even though the fluid level remains absolutely constant with zero loss or leaks.  The sender in the reservoir works fine and without fault.

What can I do?  What have I missed?  In using the "search" function I see that some have mentioned bleeding the ABS pump using VAG COM software and lead (which I don't have).  Has anyone been there, and can help?

Cheers,
Lotuschris

[harlemex]

go through the bleeding process again, this time using the two man method ie without the pressure bleeder would be my next step.

[gti_boz]

you need vagcom to opperate the abs unit.. or if your car is in a wide open space get the abs to kick in by driving it (slowly of course lol).. then re do the bleeding process

[eddie_t]

I've been in the same position, annoying isn't it. I recommend getting a Vacuum bleeder as they are far superior to the pressure bleeders IMO. For some reason they're hard to come by in car shops but they're on the internet (look at Mityvac) although in the end I used a mates home made vacuum bleeder.

[Wazzzer]

brake bleeding seems to be a dark art on the VWs

[Lotuschris]

Thanks for all the really fast replies guys.

I did the "old fashioned" two man approach first, but with the pedal still soft I got out the pressure bleeder and started again from scratch.  It is still no better, and it has been done several times over "both ways".

I know the VAG COM is the next step, but I dont have it and for the number of times I would use it it is not to my mind worth purchasing?

Otherwise might have to consider a "suck job" as opposed to a "blow job" in how to bleed the fluid through the system as suggest? 

[gti_boz]

i know it sounds dodgy lol but making the abs work then re bleeding works ive done it on a few vw,s as i also dont have vag.com

[houston]

did you pull the old fluid out of the reservoir? i made the mistake before of bleeding but without pulling as much old fluid out of it as i could first and it took AGES!!!

is the brake cylinder working? pump the brake pedal to get it firm then with it held start the car, ts should drop about an inch, if it doesnt, then cylinder at fault, if it sinks further then it needs bleeding again.

[Prawny]

I did the "old fashioned" two man approach first

that's it f**ked then!

Bleed the brakes on a mk4 using that method basically kills them. what happens is, over years of use (most are 10 years old now) the master cylinder becomes rougher further down there bore where the piston usually does not reach, so when you do the old school 2 man method of bleeding the brakes, you push the piston into unknown territory in the master cylinder. The seals tend to pick up on this roughness and flip over, then the whole lot is scrap.

You'll most likely need to rebuild the master cylinder, or for the sake of a few quid just get a new one.

[phatsam2003]

Don't you need to bleed the clutch as well??