# I'm converting to air brakes if I can't figure this out. Soft Pedal/poor braking.



## InspiringTech (Sep 9, 2002)

Car: '92 VW GTI w/ VR6 and 5lug swap. 
Problems/Symptoms: Initially I noticed it was taking more pedal travel to stop my car. Then I noticed the pedal was not returning as quickly as usual (after depressing the pedal). On my way home from work a while back, it was clearly getting progressively worse, to the point where I pulled over to get it towed home. Get home, and starting playing with it. With the car running, if I depressed the pedal with moderate to heavy pressure, it would fairly quickly sink to the floor. I was still getting SOME braking but it was barely enough to stop the car before the pedal hit the floor. We discovered a small leak on one of the rear pas. lines. So awesome, we'll tighten it up, bleed all four and be on our way. WRONG. This is where it begins.
Things we have tried, and procedures we have used: Normal bleeding process, using a pressure bleeder, starting with the furthest from the MC working out way up. We also bled the clutch, just because we were there. Pedal was lightly improved but clearly still an issue. Of course if you pump a couple quick times the pedal will stay hard. So we re-bleed, re-bleed, and re-bleed with no improvements. We tried it with the pressure bleeder, without the pressure bleeder, we tried replacing the MC with a known good one, then with a brand new one. We read up on the vortex and got all kinds of ideas in our heads, so we bypassed the proportioning valve, and still nothing. We unmounted the rear calipers (with them still hooked to the lines) and bled them witht he bleeder screw being the highest point, and still nothing. The brakes will be firm when the vehicle is off, but the second you start it, the pedal sinks to the floor and takes forever to return. 
It's been so long and we have tried so many wierd ass things that I'm starting to forget the basics, as well as everything that we actually did. So, now the car has sat for about a month and half and hasn't been touched and I want to be able to drive it on nice days again so please any help or more quirky things we can shoot for would be appreciated.


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## Terrible One (Apr 25, 2002)

*Re: I'm converting to air brakes if I can't figure this out. ... (InspiringTech)*









fresh.


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## InspiringTech (Sep 9, 2002)

*Re: I'm converting to air brakes if I can't figure this out. ... (Terrible One)*

Good lookin' out on the picture post. There she be in all her non-stoppingness. Man, I was such a nicer person when that car ran. Help?


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## Terrible One (Apr 25, 2002)

*Re: I'm converting to air brakes if I can't figure this out. ... (InspiringTech)*

Don't kill yourself over it just yet, just haven't found the culprit and when its said and done the downtime will be worth it for sure man.


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## InspiringTech (Sep 9, 2002)

*Re: I'm converting to air brakes if I can't figure this out. ... (Terrible One)*

As usual I'm sure it's more basic then turning a MAF around, yet we can't figure it out. We might be able to rebuild a motor and make it run in half a day but it doesn't do us didly if the thing doesn't stop haha.


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## VWTattoo (Apr 25, 2001)

*Re: I'm converting to air brakes if I can't figure this out. ... (InspiringTech)*

Well, I came back into the brake forum to update my thread about my 84 Scirocco, and what the results were that fixed a VERY similar issue to yours, so maybe this will be of some use to you. 
Have you tried a new booster yet? The problem I had, after replacing EVERYTHING ELSE in the braking system (Yes- *everything*!) was exactly the same as yours. Rock hard pedal when the car is not running, you fire it up, then the pedal swould sink to the floor. Turned out to be a bad Vacuum Booster. Yeah, the "usual" diagnosis of "No booster = hard as heck brakes" doesn't apply for this, which I still don't understand, but somehow the booster was replaced and all is 100% right again. 
Especially the returning back to stock position problem for your car also sounds like a booster issue.
Maybe this is your problem- Good luck!


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## InspiringTech (Sep 9, 2002)

*Re: I'm converting to air brakes if I can't figure this out. ... (VWTattoo)*

Thanks for posting http://****************.com/smile/emthup.gif I guess I'm just more aggrivated as to why I don't understand how a booster would cause this problem, simply because of what it's purpose is in the setup. However, I definitely have spares laying around the shop and we're gonna give a swing at it this weekend. I'm officially running the booster over with my truck if that's the problem. I'll be sure to reply with our results, and pics if necessary


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## VWTattoo (Apr 25, 2001)

*Re: I'm converting to air brakes if I can't figure this out. ... (InspiringTech)*

I agree with your confusion of this, and I agree that this is an unusual symptom, but this was the main issue with the sponge for a pedal, according to my garage. I'll be watching to see if this works for you, too- Good Luck! http://****************.com/smile/emthup.gif


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## 2 doors (Jun 18, 2003)

*Re: I'm converting to air brakes if I can't figure this out. ... (InspiringTech)*


_Quote, originally posted by *InspiringTech* »_ The brakes will be firm when the vehicle is off, but the second you start it, the pedal sinks to the floor and takes forever to return. 


This statement made me think booster too. That seems to be the only thing that would change depending if the vehicle is running or not.


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## VWTattoo (Apr 25, 2001)

*Re: I'm converting to air brakes if I can't figure this out. ... (2 doors)*

^^^ Agreed- waiting for the update, too! (Fingers crossed for him, hoping it works!)


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## InspiringTech (Sep 9, 2002)

*Re: I'm converting to air brakes if I can't figure this out. ... (VWTattoo)*

Well guys sorry for not getting back to the thread for updates, but we weren't able to get to it this weekend. I will for sure be doing it tomorrow night though, late after I get off work. Will keep you posted Scott. http://****************.com/smile/emthup.gif


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## InspiringTech (Sep 9, 2002)

*Re: I'm converting to air brakes if I can't figure this out. ... (InspiringTech)*

We got the old booster out late lastnight, but haven't got the new one back in yet. Everything "APPEARS" to be normal, but we're still going to swap it out to see. Still got my fingers crossed. 
Anyone else have other ideas? 


_Modified by InspiringTech at 7:22 PM 1-29-2008_


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## InspiringTech (Sep 9, 2002)

*Re: I'm converting to air brakes if I can't figure this out. ... (InspiringTech)*

So, we slammed it out tonight, and re-bled yada yada, and still nothing. The problem persists. We're going to swap out calipers next (even though after peaking in the seals none of them "appear" to be leaking), because at this point I'm desperate to have it back on the road







http://****************.com/smile/emthdown.gif















For the record, I know I'm now that guy that just throws parts at a car 'til it's fixed, but I don't care, any logic was thrown out weeks ago haha. Everybody have a good, safe weekend










_Modified by InspiringTech at 9:57 PM 1-31-2008_


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## VWTattoo (Apr 25, 2001)

*Re: I'm converting to air brakes if I can't figure this out. ... (InspiringTech)*

Throwing parts at it is *exactly* what happened on mine, bro. It took 5+ weeks to throw every part at it possible until they finally worked. Was it actually the booster?- I don't really know cause I didn't do the work. PArt of me thinks it was, the other part thinks there was more going on than they told me.








Sorry the booster didn't help- it was what they told me it was, and was the last part left to throw. Do yu still have rubber lines, or are you using SS ones? IF you still have rubber ones, you could try the clamp technique on the lines to try and eliminate corners until you find where the problemo is. Oh, and was there brake fluid inside the old booster? 
Hang tough...








Scott


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## InspiringTech (Sep 9, 2002)

*Re: I'm converting to air brakes if I can't figure this out. ... (VWTattoo)*

Good to hear I'm not alone. No fluid in the booster, and I have SS lines, well kinda. We're running part SS part rubber right now cause we had some previous issues with some of the SS lines I had before and are having new ones made. Our next step other then parts hucking, is to just eliminate corners until the problem goes away. We're just going to cap one line at a time using a bleeder screw so it can still be bled, and by process of elimination figure out what section is problematic.


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## VWTattoo (Apr 25, 2001)

*Re: I'm converting to air brakes if I can't figure this out. ... (InspiringTech)*

Misery loves company, eh?















I hear you man- I was so frustrated over it, too, but something has to be the problem. I'd start with the RR and see what it gets you, since the RR and LF are on the first stage of the MC stroke, and the RR has the longest line to bleed. It also has the most PITA brake line location, too, and usually requires dropping the rear suspension to get at it in order to swap it out. 
Keep at it, man, and let me know what the F you figure out.








Scott


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## Terrible One (Apr 25, 2002)

*Re: I'm converting to air brakes if I can't figure this out. ... (InspiringTech)*

The GLI is turning into a brake parts car damn't, this is getting stupid.


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## 86Sir.Rocco (Oct 13, 2006)

hmmm at first i thought maybe the master cylinder cuz u said it slowly sank to the floor, indicating a bad seal in the cylinder, but then u said u swaped it with a good one and it did the same...


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## Terrible One (Apr 25, 2002)

*Re: I'm converting to air brakes if I can't figure this out. ... (VWTattoo)*


_Quote, originally posted by *VWTattoo* »_Throwing parts at it is *exactly* what happened on mine, bro. It took 5+ weeks to throw every part at it possible until they finally worked. Was it actually the booster?- I don't really know cause I didn't do the work. PArt of me thinks it was, the other part thinks there was more going on than they told me.








Hang tough...








Scott

Scott- Do you know if they bench bleed the master cylinder after installing the booster?


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## VWTattoo (Apr 25, 2001)

*Re: I'm converting to air brakes if I can't figure this out. ... (Terrible One)*

I think they may have, as they pulled the new MC off of the old booster before they had received the new one to get ready for it. I could try to find out tomorrow for you. I have read that you would probably want to do this, so you aren't pushing air from the MC all the way through the lines, which would take a lot of bleeding. 
Did you bench bleed your new MC?


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## Midwesterner (Sep 9, 2003)

*Re: I'm converting to air brakes if I can't figure this out. ... (VWTattoo)*

I had the same problem and I rebled the brakes several times, replaced the rear calipers (started after I did some rear brake work) and I finally figured it out.
I replaced the one way vacuum check valve and it fixed the problem.


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## InspiringTech (Sep 9, 2002)

*Re: I'm converting to air brakes if I can't figure this out. ... (Midwesterner)*

Check Valve should not cause this problem, unless installed backwards







, but I guess it IS one of the few things we haven't swapped out. It's a good thought, that's for sure







.


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## Midwesterner (Sep 9, 2003)

*Re: I'm converting to air brakes if I can't figure this out. ... (Midwesterner)*

A malfunctioning vacuum check valve at the booster could (and did for me) cause the same problem you're having. It was on my 92 GTi 16v.


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## InspiringTech (Sep 9, 2002)

*Re: I'm converting to air brakes if I can't figure this out. ... (Midwesterner)*

Heck, I'll give it a shot. We've got to rig up a stock one to make it work cause the vac. port is not in the stock location but what the heck. Like I said, I'm willing to try just about anything. Thanks.
Gerry


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## InspiringTech (Sep 9, 2002)

*Re: I'm converting to air brakes if I can't figure this out. ... (InspiringTech)*

Threw new pads on up front just for good measure. Re-bled again and no change. I did however get a chance to take it out and beat on it a little bit to get my spirits up, but with no brakes the fun doesn't last very long


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## HilF (Jan 10, 2004)

*Re: I'm converting to air brakes if I can't figure this out. ... (InspiringTech)*

i'm watching this thread. hopefully you find a resolution


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## InspiringTech (Sep 9, 2002)

*Re: I'm converting to air brakes if I can't figure this out. ... (white_r!ce)*

Haven't had a chance to get to it still, I've been working on getting my girlfriends car back on the road thanks to the lovely VW auto tranny's, but this long weekend will help. Just hoping for any new ideas?


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## red_rock_beetle (Sep 9, 2007)

*Re: I'm converting to air brakes if I can't figure this out. ... (InspiringTech)*

this may be of no help to you but...
whats wrong with air brakes on a dub?








i think it would be cool http://****************.com/smile/emthup.gif


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## InspiringTech (Sep 9, 2002)

*Re: I'm converting to air brakes if I can't figure this out. ... (red_rock_beetle)*

Air brakes would be rad on a dub, but to be honest I know little to nothing about them, and I'm sure the setups aren't exactly super light. 
However, what I do know is that my F'n brakes are back! It sat for a while because I've had other things to take care of, but we got a couple hours in last night and all is finally well. I still don't know EXACTLY what the problem was, but I can tell you that it was fixed sometime while messing with the back brakes (as most people have said, "it's probably something in the rears"). I got a local hydraulic shop to build me a little brake pressure gauge with a piece of hose on the end, so we could try to track down the problem. Whilst hooking it up and trying to get an average reading, we noticed that after bleeding the backs a couple times, there was a drastic improvement. So, we chucked the wheels on and and took it out, and whata ya know, everything was 100% once again.








So to recap: All we did is hook the gauge up on both sides once each, to get a feel for it (bleeding after each time we disconnected the gauge), and next thing you know we're golden. This was also probably some of the hardest I had ever pressed on a brake pedal (during the "gauging" process) as I was trying to find a peak number that we were reaching. The brakes were bled manually, not using my pressure bleeder, and we only did the backs.
Now the only problem is that I've still got my proportioning valve out haha







. So we'll see what comes of having to re-bleed, hopefully nothing at all.


_Modified by InspiringTech at 4:41 PM 2-27-2008_


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## [Oo=MK2=oO]macelius (Feb 1, 2006)

i was thinking vacum leak, but sounds like there was a big air bubble back there.


_Modified by [Oo=MK2=oO]macelius at 3:12 PM 2-28-2008_


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