bleeding brakes

[gti69]

Hi guys

I have a 91 mk2 Golf GTI with an ABF engine instead of the underpowered 8v engine it replaced
My problem is the brakes, everytime i bleed them (using the 2 man method, pump, lift etc) they are fine for maybe a couple of days and then go back to being really soft and full of air. i find i have to pump the pedal to get a decent feel from them. When first bled they are great and feel how they should do but over time (2-3 days) they go back to how they were before i bled them. 

I have a master cylinder from a late 16v golf (was brand new), G60 hubs, discs and calipers, basically a complete g60 brake setup. I also have goodridge braided hoses. I have checked the fluid reguarly and as far as i can see there is no fluid escaping from anywhere.

Any suggestions would be great. Thanks guys,
Kris

[...joe]

did you push the lever type thing on the pressure regulator backwards before you bled the brakes? this can make a diffenence. also the goodridge hoses can make bleeding harder for some reason i cant remember! i have the same set up as you and in the end i got a friend to do mine with a pressure bleeder. might be worth getting a gargae to use theirs as like you i couldn't get the pressure right either.

[Mr Blue]

I had this problem a few weeks ago. Turned out to be the vacum unit behind the master cylinder. it was sucking in more air than a vacum cleaner!  

I bled them using an airline and the 2 man way with no luck. Change the master cylinder first and if that doenst work then it could be the vavum box or a split in the hoses?

[gti69]

Thanks for the suggestions guys.

When i was bleeding the brakes i made sure the bias valve was fully open.

I will get a new master cylinder as the one i got was just a cheap pattern part. Thats probably my problem!

[diagnosis-dub]

Never buy pattern parts for things like that, although VW are expensive you know it will work.

Just get yourself down to halfords and buy a brake pressure bleeding kit. costs about £20 if I remember correctly and you use your spare tyre to make it work.

Check your bleed nipples on the back calipers if you have had these changed or done work on them as a lot of the ones I have come across weren't sealing when tight and I got the problems you discribed

[gti69]

Fitted a genuine 16v master cylinder yesterday (£81! ouch!) and the problem is still there. Admittedly it's not as bad but it's still there. Back to the drawing board me thinks

[diagnosis-dub]

When I changed my rear calipers I couldnt get the peddle to sit nice and high and it kept moving down like their was air in the system. What I had to do was clamp the brake valve so it didn't hinder the flow and leave the rear of the car overnight on axle stands on their highest setting so that the rear calipers were the highest point in the system and hopefully would collect the bubbles of air present.

Came out in the morning and pressure bled it all again and it solved the problem, I think the pressure valve acts as a trap and catches the air bubbles so its a nightmare to get them out.

Also I found that after doing the brakes a couple of emergency stops brought the adjusters in the rear calipers right up and theres hardly any movement of the pedal before the brakes start working.

One I thing I would say is check the fit of the bleed nipples in the rear calipers as I have had a problem before where the nipples dont actually sit tight in the caliper when tightened up and allow air to bleed in. Try loosening them a little and rocking them in the caliper and see how much movement there is.

[Horney]

Another thing. Which fluid are you using? I know many people who have suffered terrible problems using silicon brake fluid (AP go as far as to say never use it on their website).

Nick

[Horney]

Here ya go check this out:-

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=4147