85euro928

I recently added S4 brakes to the rear. During the "upgrade" the rear brake lines were left open and whatever brake fluid that could come out did.* Subsequent to the install I bled the rear brakes using both a Mityvac (unsuccessfully) and then the pedal-pumping method but the pedal still felt spongy like there was air in the lines.* I then bled all four corners using only the pedal method as I couldn't get a good enough seal on the bleeder screw for the Mityvac to work to my liking.* My question is, how much of the fluid would drain out of the system with the rear lines open?* Would it drain enough that I would need to bleed the master cylinder?* I'm asking because I bench bled the master before I reinstalled the engine last Spring and would rather leave it be if I could as I doubt I'll get a better bleed than that. Also, the clutch seems to work fine???* Anyone have any ideas?

WallyP

Best answer would be a question - How much fluid was in the master when you started bleeding the system? A long-term leak can drain the brake system entirely.

85euro928

Unfortunetly I didn't check before I topped it off and started bleeding. I was hoping maybe some air is trapped in a high spot somewhere towards the back but if all the fluid can drain out then I guess I need to start at square one and bleed the whole system. Ugh.

dr bob

Thom--

Does your car have ABS? If so, there's the interesting possibility that you will have air trapped in the ABS unit. Fluid lines from the MC run slightly up hill to the ABS unit, from there the rear line goes down to run on the frame rail to the rear, where flow is split to each rear wheel. There are high points in that rear section where the flow splits, exacerbated when the car is raised to bleed with calipers hanging low on the suspension.

I spent the best part of two hours carefully disconnecting and combo pressure- and vacuum-bleeding my system section by section as part of the Great 100k Brake System Overhaul in the spring. It was the only way to restore a high hard pedal after having everything apart and drained. In the process, I managed to push four liters of fluid through all the plumbing. Pedal is better than I ever remember it being in the past, and I've owned it since 22k and original pads. This is a tedious and sometimes messy process, but worth it for the great results.

brianrheffron

When doing any work on brakes I top up the fluid to the brim
then fit a spare reservoir cap with the air vent hole sealed up.
Air can't get in at the top so very little fluid drains out when you
crack open the system. It's a simple fix but it works very welll.
My spare reservoir cap came from a VW in a breakers yard,
can't remember which model.

85euro928

Doc,
No ABS, or at least I haven't found any evidence of it in the last 4 years. I did try jacking up each corner but that may have made it worse, as you noted the suspension was hanging. I've run 2 liters of fluid already through the rears alone which is a shame bc I flushed the system when I bought the car and again last Spring. Thinking about it I'm gonna try pressurizing the reservoir while having each corner of the car and suspension raised. If that doesn't work I'll break down and bleed the MC. There's no way for me to take apart the lines to bleed each part of the system seperately as the fittings are frozen to the lines, so unless I want to replace them that's not in the cards. Also, just to note, the car stops fine, I just don't like the pedal, never really have.
Thanks

85euro928

Brian,
Wish I had thought of that

928Myles

Thom,
have you tried useing a power bleeder on the system. Throughput is lot higher than either pedal or mityvac bleeding and can push trapped air through more easily (it is also a continous flow rather than start / stop).

Myles

tilac999

The best tool I have purchased lately is the Motive Power Bleeder. I flushed my ABS brake system and clutch slave very easily. Try it and you'll never go back to any other way. Good luck with your Euro.

jpitman2

I have recently used the Motive power to flush the system, and it came up rock hard immediately. In the past I have changed stop light switches (the hydraulic ones) with a blocked air hole in the cap, and not needed to bleed anything.
jp 83 Euro S AT 54k

dr bob

Somehow in the past, while doing the annual brake fluid flush, I managed to get some air in the system. I've been using a power bleeder but ended up with a low/soft pedal. Since then it's still been flushed with the power bleeder annually, and while it has gotten better, it was never at full pedal height and firmness as when new. Nicole went through a similar situation a few years ago, and tried lots of different ways of flushing and bleeding with unsatisfactory results before taking it to a shop that was able to somehow get the air out.

I was replacing brake hoses anyway, so I slipped some vacuum tubing onto the stub ends of the steel lines, closed them with a hemostat. It's what they are really for, to pinch an artery and stop the bleeding, right? Then worked my way through the system, with a vacuum bleeder at the high point and the pressure bleeder at the low point of each section. Pull a vacuum to make air pockets really big, then open the hemostat "valve to let fluid push through and fill the line. Did every section, the ABS pump, and did a manual bleed of the MC with the vacuum bleeder on each hose port plus the front section bleed port. The calipers were rebuilt too, so were empty. The were pushed full of fluid from the system, with calipers supported high so any air would rise into them. I twisted and turned the calipers in different orientations as I bled each one, to make sure that any air would find a way to a bleeder port.

It worked, where pressure bleeder alone and vacuum bleeder alone had failed previously to get the last little bit of air out. Just a couple hours and several liters of brake fluid.

Jim Devine

Try tapping on the caliper with a plastic hammer as you bleed it- sometimes helps to dislodge air bubbles. Also don't pump hard/ rapidly-
it just makes it worse.

85euro928

Thanks for all the advice. I'm going to try again this weekend and I'll report back.
On another note I'm curious about ABS. Brad, your sig notes you have ABS on your Euro, does anyone know if ABS was a factory option in '85? I would think if I had it they'red be a controller someplace, or at least I light in the instrument cluster?

AirtekHVAC

Good luck Thom....I dread the "bleeding" when I replace my clutch master and slave, as well as the brakes...

dr bob

The ABS unit lives in the top of the LF wheelhouse on LHD cars, with the hydraulic connections protruding into the engine bay slightly. Follow the brake plumbing forward from the master cylinder. If you have ABS, plumbing goes to that unit before it goes to the frame rails.