Inconsistent and spongy brake pedel feel.

[OhioPerformance]

Long shot but did you bleed your clutch?

 

[woodardhsd]

Long shot but did you bleed your clutch?

No, it's a DSG car.

 

[OhioPerformance]

Copy-Missed that part. Your system is a closed however it can still draw in air - sounds odd but have you checked your brake fluid cap? You have bled that system so many times it hard to believe there is still air in them. I did have a caliper that required 2 quarts of fluid before I felt it was ok.

 

[woodardhsd]

If it still seems like it could be related to the rear, you could always pull the hard lines for the rear at the pump and plug it, then go for some short drives with only the front brakes and see how that changes things. Obviously be safe, at your own risk, Yada Yada.

So I've been trying to figure out how to do this without killing myself. The manual says the ports on the ABS unit that feed the rears are different sizes. Both left side ports are M10, and the right side are M12. I was able to find M10x1.0 plugs, but not M12 ones. So all I would really be doing is testing the left side. Even then, I'm not sure if the results would mean anything. Basically, the MC would still be sending the same amount of fluid out as usual, but it would only be going to 2 calipers istead of 4. I would think that those two calipers would receive twice as much fluid as usual and may appear to be working better than they actually are.

On the getting VW to do something front, I got customer care involved in the process. The service manager of the original dealership agreed to look at the car himself. He drove it yesterday and initially said the brakes felt OK to him. I told him I disagreed and asked if we could look at the used MK8 GTI they had for sale on the lot. We both drove it and after that, he agreed that my pedal felt a little longer than the MK8's did. I tried telling him that's how they're supposed to feel, and that's how all 7 or 8 GTI's I drove have felt. He still wanted to argue that my brakes were fine even after driving the newer one. He said that since he can't think of a part to replace to make the pedal feel better, there's not much he can do. He did day he was going to check with his VW corporate guy and see if he has any suggestions.

 

[GTIfan99]

So I was able to get better clutch, brake pedal, and suspension feel, and fixing my oil consumption on track by upgrading my....


Entire car to a mk8. ???

 

[victorofhavoc]

Sounds like typical dealer brushoff.


If you plug the rears the fronts won't get twice as much fluid. The fronts need far more fluid to move and they're already built to appropriate a ton more pressure up front. Abs would likely catch it and stop from overshooting fluid, but even if it didn't you'd only get maybe 10% more.

If you're getting air in, it has to be coming in from somewhere. I don't think it matters how you eliminate sources, or in what order, but I'd recommend going pre or post abs by turning off lines one by one. You likely don't even have to drive the car, just idle it for a bit giving it pressure on and off, then let it sit, come back to repeat. Replicate it as best you can and then narrow down further from there. There's not much else you can do other than go part swapping for fun. I guess you could just swap the whole system.

 

[victorofhavoc]

So I was able to get better clutch, brake pedal, and suspension feel, and fixing my oil consumption on track by upgrading my....


Entire car to a mk8. ???

If i had significant issues like some folks, I'd be soured on the brand entirely and move on to something else. There are many other cars out there. I thought the gti had some rattles, but my acura is so much worse it's not even funny. I've never been soured on a car because of rattles, but this car is really starting to push me there, lol. I regret not getting the m3 instead, ?. Mk8 still feels like a step down from 7. Hold strong 7s! It's the last good golf, lol.

 

[GTIfan99]

If i had significant issues like some folks, I'd be soured on the brand entirely and move on to something else. There are many other cars out there. I thought the gti had some rattles, but my acura is so much worse it's not even funny. I've never been soured on a car because of rattles, but this car is really starting to push me there, lol. I regret not getting the m3 instead, ?. Mk8 still feels like a step down from 7. Hold strong 7s! It's the last good golf, lol.

My 92 GTI 16V they forgot to properly tighten engine mounts. 3rd day heard a clunk backing out of the driveway. Pulled away in first and the engine tried to exit through the hood. Good times.

 

[victorofhavoc]

My 92 GTI 16V they forgot to properly tighten engine mounts. 3rd day heard a clunk backing out of the driveway. Pulled away in first and the engine tried to exit through the hood. Good times.

Wowza. Thankfully, I've never had a personal horror story that bad.

Worst I've seen happen to someone is when a sears forgot to put lug nuts back onto my friend's dad's car. He didn't notice, and exiting the sears parking lot he was very confused why his car clunked and wasn't moving. Meanwhile someone seemed to have lost a wheel rolling down the road in front of him. It was on a hill that led to a major intersection so that wheel kept going like the energizer bunny. Sears said they'd happily put the lug nuts back on for him and he could have the oil change money refunded (tire rotation was free). No mention of his bumper, rotor, brake caliper, cv axle, subframe, trans mount, or radiator and grill though. ?

 

[woodardhsd]

Sounds like typical dealer brushoff.


If you plug the rears the fronts won't get twice as much fluid. The fronts need far more fluid to move and they're already built to appropriate a ton more pressure up front. Abs would likely catch it and stop from overshooting fluid, but even if it didn't you'd only get maybe 10% more.

If you're getting air in, it has to be coming in from somewhere. I don't think it matters how you eliminate sources, or in what order, but I'd recommend going pre or post abs by turning off lines one by one. You likely don't even have to drive the car, just idle it for a bit giving it pressure on and off, then let it sit, come back to repeat. Replicate it as best you can and then narrow down further from there. There's not much else you can do other than go part swapping for fun. I guess you could just swap the whole system.

I'm not sure I'm going to try plugging various ports and testing that way. I could only find plugs for the M10 ports, not the M12 ones. Not really interested in damaging something by threading the wrong fitting somewhere.

I did decide to give bleeding the brakes another try this weekend. Before doing a manual bleed, I thought I'd try to run the ABS pump with VCDS again. I made sure to have the bleed screws open on both front wheels. No air came out initially, but after letting it gravity bleed following the pump running, a massive amount of bubbles came out both sides. I folllowed that up with a 2-person bleed. I had gone back through the service manual and read where it says that the helper should make sure the pedal went to the stop. I had never made sure of that before. After doing all that, the brakes are back to feeling like they should. Now the only question is how long will they stay that way.

That leads me to my next question. Is it possible the air was in the system the whole time, and maybe that there's not a leak? I don't understand all that goes on inside the ABS module, but is there a place the air could "hide" inside the system where it wouldn't effect the brakes one day, but then it moves to a different area and causes a soft pedal? I don't understand how I could have a leak that only lets air in, not fluid out. The pressures inside the brake system are so much higher than outside air pressure.

 

[victorofhavoc]

I'm not sure I'm going to try plugging various ports and testing that way. I could only find plugs for the M10 ports, not the M12 ones. Not really interested in damaging something by threading the wrong fitting somewhere.

I did decide to give bleeding the brakes another try this weekend. Before doing a manual bleed, I thought I'd try to run the ABS pump with VCDS again. I made sure to have the bleed screws open on both front wheels. No air came out initially, but after letting it gravity bleed following the pump running, a massive amount of bubbles came out both sides. I folllowed that up with a 2-person bleed. I had gone back through the service manual and read where it says that the helper should make sure the pedal went to the stop. I had never made sure of that before. After doing all that, the brakes are back to feeling like they should. Now the only question is how long will they stay that way.

That leads me to my next question. Is it possible the air was in the system the whole time, and maybe that there's not a leak? I don't understand all that goes on inside the ABS module, but is there a place the air could "hide" inside the system where it wouldn't effect the brakes one day, but then it moves to a different area and causes a soft pedal? I don't understand how I could have a leak that only lets air in, not fluid out. The pressures inside the brake system are so much higher than outside air pressure.

The two person bleed is basically the last ditch effort to try and get the air out of the cavities around the bleeder, at the top of the caliper, and in the abs pump. It works pretty well because it's forcing more fluid through and that helps break up bubbles.

The air could have been in there the whole time. I've had very poor luck with power bleeders when using them wet (with fluid in the bleeder) vs using them dry (fluid only in M). My suspicion is that with fluid you get leaks on some of the seals and a slight bit of "pull back" when you stop the bleed which sucks fluid (bubbles) back and forth inside the line. Any present bubbles that got pushed loose will then move back into the top cavities they can find.

Fluid in the abs pump typically happens when someone let's the Mc go dry during bleeding or the pressure system forces some air in. It can get very stuck in the pump, and the pump sometimes needs to move in order to force the bubbles out of the cavities and into the main line. In the olden days before fancy things that forced pump activation, it was fairly common for people to bench bleed the pump and/or master cylinder with very stuck bubbles.

 

[golfdave]

Have you tried this method in the VW workbooks?

 

[woodardhsd]

Sure have. I tried pressure bleeding in the VW order (LF, RF, LR, RR) and the traditional order (RR, LR, RF, LF), and I've tried manually bleeding both ways.

 

[lars3010]

I’ve been experiencing the same problem with my 2018 A5 Sportback for over six months now. I’ve been to the Audi dealership workshop twice, but they told me the brakes are working fine. I’ve bled the brakes multiple times myself, and the workshop has also carried out ABS bleeding. However, I’m still facing the same issue. Interestingly, when the car is parked on a hill or driving downhill, the brake pedal feels as it should again. Additionally, when I pump the brake pedal while braking, it feels the way it should.

Now, my question to the thread starter: Did the last bleeding and removal of air from the ABS block resolve the issue for good, or has the brake pedal feel deteriorated again?

 

[woodardhsd]

Nothing has worked (long-term) so far. Occasionally replacing a part or bleeding will result in an improved pedal feel, but it never lasts more than a day or two. As of now, the car has had a second master cylinder replacement and new front pads and discs, provided by VW. I have also replaced the rear pads, lines, rotors, and calipers. I had assumed that the black material that would appear in the brake fluid at the rears was somehow related to the rear, but even with those new parts I'm still seeing the black fluid. Not sure where it could be coming from, other than the ABS unit. After I raised absolute hell with the dealership and the VW rep they sent down, they agreed to order and replace the entire ABS unit. I'm not sure what else it could be, and honestly, if this doesn't fix it, I'm done with it.