Brake Pedal Firm When Engine Off, Spongy With Engine Running - Now No Fluid Appearing When Bleeding

[Risocco]

Following on from this...

http://sciroccoregisterforum.co.uk/carf ... 10&t=13571

Having had my caliper rebuilt and fitting a new hose my caliper was still binding to the point of halting the car.

Then turned my attention to the master cylinder/servo/linkage area. So took off the 16v set up run the original servo/MC. Fitted it all up, bled the brakes till no more bubbles in the fluid, pedal was firm so naturally thought jobs a good one!

Fitted the wheels turned the key drove off and have a spongy pedal again with no braking power what-so-ever, except the hand brake.

Bleed them again, same problem. Bleed them again, plenty of bubble free fluid comming out, pedal feels strong but the second the engine starts the pedal goes spongy.

So I have gone from brakes sticking on to having none at all. Great.

Feels almost like I need to keep bleeding them, but the last few times there were no bubbles in the fluid?

Any help much appreciated guys, really am losing the will with this car

[wasted]

It must be something to do with the servo I reckon, if the pedal only feels spongy when the car's running.

Looking elsewhere, I did find this topic:

http://www.vwgolfmk1.org.uk/modules.php ... ic&t=96595

Sounds very similar to what you're experiencing, and the end result was a new servo fixed the fault. They did also specifically advise to check the pipe coming from the servo for leaks, as well.

[the edmundator]

On my bronze GTI, I had a new master cylinder, wheel cylinders, pipes and fluid, and reconditioned calipers. The resulting increase in efficiency proved too much for the old servo, which failed, giving me a very soft pedal with minimal braking effort. A new servo did the job.

[Risocco]

Cheers boys.

new servo time then. Basically, the 1.6gt servo not powerful enough to aid the bigger brakes then? What are the bolt on options then guys? Obviously the 16v is an option but that involves messing with the clevis arms again.

Any help much appreciated guys

[wasted]

Would a standard 1.8 8v servo not do the job? Should just be a straight swap.

[Risocco]

Sound, so the 1.8 is larger than the 1.6 one?

[wasted]

Actually having checked, it's not - the 1.6 and 1.8 engines both used a 7" servo I think.

Several people on the mk1 Golf forums recommend using a Mk2 golf servo - they're 9".

Details here:
http://www.vwgolfmk1.org.uk/modules.php ... age&pid=40

[Risocco]

Ahh fair do's. Right back to the 16v servo then. Checking the prices of a new 7inch servo made me eyes water! Will try again then, ta for the help!

[the edmundator]

I'd try another standard servo first - easy way to test that's definitely the problem.

I'm sure someone could find you a spare to try.

[wasted]

Fair point actually. You should be able to find a decent one for a few quid, just to be sure.

[Risocco]

OK, tried a new servo, now when you go to bleed them, a touch of fluid comes to the top of the nipple on the caliper but won't travel any further.

WTF?

Seriously WTAF?

Losing interest in this car big time which I never thought I would say.

Any help before I set fire to it would be more than welcome.

[Tim_R]

Sorry I haven't re read all the threads so you may have covered this already.
Are you using 16v calipers, MC and servo?
If you are did you shorten the 16v servo rod by 10 mm before fitting the mk1 clevis? The mk2 golf clevis is a fair bit shorter than the rocco one and will cause the brakes to bind if the rest of the linkage is set to factory measurements and the rod is as it left the factory.
When you rebuilt the brake linkage, did you take measurements of the length of the rods before stripping it and rebuild it back to the same dimensions?

My mk1 rocco and golf Haynes manual only gives the dimensions for the pedal to drivers side bell crank rod. 172mm for the later chassis numbers. I can't find anything about dimensions in my mk2 manual.

HTH

[Risocco]

Hello Tim, long time no speak, trust you are good.

Yeah, noticed that the threaded rod from behind the servo was longer on a 16v, took a bit off with the hacksaw as I was worried that the return spring would not fit in the hole.

Took measurements from the original GT servo, measured 132mm from rear servo body to end of the hole on the clevis where the pin drops in place and made sure the 16v one was the same distance with the GT clevis fitted. I believe this should be correct will, post a thread asking for clarity from another GT.

Am leaning towards what you say in regards to the linkage being out of sync now. I didn't adjust the rod that runs across the bulkhead, well not knowingly anyway, so thinking I could do with fitting another to ensure factory distances are kept.

In terms of the linkage, are MK1 Golf ones the same?

Cheers mate.

[Tim_R]

I'm good thanks fella, I'll try and do some measurements on the cross link between the bell cranks which is as it left the factory as far as I know. I've certainly never taken it apart!

Pretty sure mk1 golf ones are the same.