Chasing a braking issue

[86 Syncro]

Been chasing this problem for a while now, making me nuts….I have to go through inspection before 11 AUG, or the Syncro will have to sit…AGAIN…sooooooo

I started having this issue after I changed the Master Cylinder, I have braking power, at a halt just lightly holding the brake pedal will hold the car in place, but the pedal is VERY soft, requiring me to push it almost halfway before I really get any stopping power….

I put it up on a lift today, and had a helper lightly press the brake pedal as I tried to spin each wheel, to try and Isolate the problem… Both front wheels stop almost immediately, but neither of the back wheels have much braking force, even with the Proportioning valve opened all the way…

My first thought is the proportioning valve, but I want to be sure before I spend that kind of money, since it’s not cheap…

[Chris S]

Try bleeding them again, it sounds like there is still air in the system.

[ld50]

hey – I had something similar on my gti where the pedal would sometimes work and sometimes it needed a pump beforehand. It turned out to be that the lever which triggers the proportioning valve wasn’t set up correctly (or attached at all in this case) so the valve flapped around giving me mostly “random” braking distribution…

I guess you’ve checked that the valve can move freely and is more or less correctly adjusted have you?

If you find it’s not correctly adjusted (i.e. no flow to the rear as no braking force might suggest), once adjusted you’ll need to bleed the rears again.

Crazy thing was mine had gone through the workshop and the MOT like that and nobody noticed!

[86 Syncro]

Is there a specification for checking the adjustment? I know it probably needs to be adjusted since the car is lowered….

One more question, when bleeding the brakes, the rears will not bleed unless the Prop valve is opened by hand..that means it works, right?

Also, I used a pressure bleeder to bleed the system when I did it, is that a good or bad way to go about this?

[Housey]

do it the old fashion way pump the pedal

i believe your car is non abs?

for the bleeding to be successfull, you will have to fully open the rear valve (there are 2 holes there which you can use to hold it open with a zip-tie og something equal to that)

then it should just be to either use vacuum at the bleed valves or the old style pump action airing of brakelines

shouldn’t be more to it then that

[ld50]

> Is there a specification for checking the adjustment? I know it probably needs to be adjusted since the car is lowered….

as far as I’m aware the front wheels should lock up before the rears. On mine there was a lever with a springy bit and the bolt which joins it to the bias valve had some built-in play so I adjusted it so that as the car stands the valve was adjusted to the beginning of that play (i.e. no bias adjustment).

Can’t really describe it any better and I know it’s a bit different on the syncro (this was on a 16v) but if I were to load a car full it would have a small margin and then start adusting more to the rear. I tested whether the fronts locked up first as they should and they did. Braking and sliding it feels as it should and it stops on a dime so I can only conclude it’s set up about right

> One more question, when bleeding the brakes, the rears will not bleed unless the Prop valve is opened by hand..that means it works, right?

that does sound like it’s working…

> Also, I used a pressure bleeder to bleed the system when I did it, is that a good or bad way to go about this?

I’ve only done it by slowly stepping on the brake (or having the missus do it while I do the bleed, no idea what a pressure bleeder is sorry…

[Housey]

to do the rear adjustment, you will need two gauges that connects to the bleednipples (instead of the nipples) then have someone to operate the pedal while you adjust to the values specified by vw

[Chris S]

Dan, Can you find out any more info on the adjustment values?

[Housey]

i asked when they did my rear brakes on a vw shop when i got my car licensed, but they didn’t want to tell me

[Chris S]

I will have to ask at my VW Garage

[86 Syncro]

Ok, had the brakes bled by a garage last week, and it was good enough to pass the brake test, but the brakes are still soft. He verified that my Proportioning valve is most likely OK…so that leaves either the front calipers, the rear cylinders, or the brake booster. (I have the older, non-adjustable type booster)

I have a used newer style brake booster in the garage that I’m going to install once I re-paint it. I will keep posting with updates, to help others that may someday have this same problem.

[86 Syncro]

Well…I finally fixed my soft pedal issue. It took me almost doing a complete brake overhaul to do it, but it’s sorted now.

For reference, here is the complete rear drum assembly, with the drum removed. They are set up the same as a standard FWD Golf, but obviously the parts are a bit different, to give clearance for the hub.

Here was one of the culprits, a leaky brake cylinder:

As you can see from all the crud on the backing plate, it had been leaking for quite some time. BTW, these are the ORIGINAL brakes the car was built with, all the way back in 1986….says something for the quality of these cars, no?

Here is the other issue I found (prepare to be amazed):

WTF!?!?!? These are the inner brake pads from both sides, I stacked them for the picture to show you how messed up one was. I have no idea how this happened, or how my brakes were still functioning in this condition…lol

A few lessons learned from this experience:
*A standard Golf II spring kit *WILL NOT* work with your Syncro drum brakes. The only part they have in common is the bottom spring.

*Be ready for a shock when you go to buy new drums for your Syncro, as they are around €100 *EACH*

*Loosen the adjusters on the handbrake cables before you take everything apart, this will make the whole process ALOT easier

*Apply some penetrating oil to the bolts securing the brake cylinder, and the head of the line itself, this will make removing the bolts easier (they are allen head bolts, so this is important!) and will reduce the likelihood of snapping your brake line when you go to remove it from the cylinder.

*Bleed your brakes! BLEED YOUR BRAKES WELL! It took me 3 times around with a pressure bleeder set at *2 BAR* (approx. 30psi) to get all the air out of my brakes. **DON’T FORGET TO OPEN THE PROPORTIONING VALVE WHEN BLEEDING THE REAR BRAKES**

[Chris S]

Nice work! []

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