# Brake System Diagnosis



## machschnelGTI (Jun 28, 2004)

First, a little about me to establish my credibility. I've been a professional mechanic for over 10 years, and the for the last 3, I've specialized in brake systems, as the Technical Support and Quality control director for a major brake parts manufacturer. All I do is brakes, all day, every day. 
On to the write up.
*A quick "how the system works"*
For any given vehicle, the components of the brake system are designed to work together....correctly. One must remember that when the car was new, all the components worked properly together, and generally they do an adequate job to satisfy the needs of most drivers. When a problem occurs, you cannot "upgrade" the parts of a system in hopes of a fix. 
The system worked properly before with the original spec parts, so there is no reason it shouldn't work properly again with the original spec parts. If there is a problem, diagnose it correctly, and fix it correctly, so that unnecessary parts are not replaced, and unnecessary money is not spent. Here are the common problems that I run into....and the proper diagnostic procedures to follow so that no parts will be replaced unless they can be PROVED faulty. 
*Low/spongy pedal or pedal goes to the floor:*
First, the source of the problem has to be found. Clamp off all of the rubber brake hoses, using "line locks" that be purchased cheaply at any good auto parts store. If you are using stainless steel braided lines, this procedure will not work, but I'll cover this later. By clamping off the lines, you have taken all four caliper out of the brake system. Try the pedal again....it shouldn't move more than 1/2 inch or so. If the pedal is still low, or still goes to the floor with the lines blocked off, the problem exists either in the master cylinder, or the ABS system (if equipped). If the pedal is rock solid (like it should be with the lines clamped off) skip to the next paragraph. To further isolate the problem if the pedal still sucks with the hoses clamped off, determine the thread size of the ports in the master cylinder and obtain some plugs (if plugs are not available, a bolt with the correct thread wrapped in Teflon tape, threaded in snuggly will suffice), remove the lines from the master cylinder, and plug all the ports. Try the pedal again. If the pedal still sucks, the master cylinder either has air in it, or the cup seals are worn and bypassing, possible leaking into the booster. Rebuild or replace the master cylinder. If the pedal is solid with the master clamped off, do one more test. Get a helper to loosen the plugs 1 turn each, push the pedal down 1/2 way and hold it, and have your helper tighten the plugs back up. Then try to push the pedal down further...this is to check for possible master cylinder bore damage in the middle of the pedal stroke. If the pedal sinks, replace or rebuild the master, if the pedal is still good, the problem lies between the master cylinder and the rubber hoses. Usually the only two components between the master and the rubber lines are either the ABS valve or the proportioning valve (on non ABS cars)
If, when the rubber hoses are clamped off, the pedal becomes solid, the problem exists in one or more of the wheels. Sit in the car with your foot on the pedal, and find a helper to start at one of the rear wheels, then the other rear, then one front and the other front, removing the clamps one by one. The pedal will drop when one of the clamps is removed...with the wheel removed, observe the brakes on that wheel while the pedal is depressed. If the rotor hold down screw is missing, use a couple of lug bolts with washers to secure the rotor to the hub while doing this. You should not see any movement. For example, when the pedal is released, the piston generally should not retract more than 0.5mm, usually 0.1-0.2 mm of piston retraction is considered normal. If you see the caliper, or the rotor moving more than .5mm when the brakes are applied, that is the problem, and you must determine the cause of it. Most common causes are:
*Seized slide pins:* The pins probably seized quite some time ago, holding the caliper in the position dictated by the pad wear at the time of the pin seizure, so now, after the pads have more wear, pins or pin bushings are flexing every time the caliper is actuated, and when the pedal is released, the caliper is moving back to its "relaxed" position, which will require excessive piston travel to squeeze the pads against the rotor. *FIX* = replace slide pin bushings and/or slide pins, lube properly and make sure that the caliper can float freely on the pins.
*Loose wheel bearings.* Grab the wheel and try to wiggle it, up and down, side to side. Also, check to make sure that the axle nut is tight. The axle nut holds the wheel bearing together, if the nut is loose, the wheel bearings will be lose, and may require replacement. If any play is felt when wiggling the wheel, replace the wheel bearings, adjust as necessary, and try the pedal again.....if it still sucks, look for other thing that would cause excessive piston travel on that wheel.
*Pads are not installed correctly in the caliper....*I know it sounds stupid but I've seen it. Make sure that the pads are not bent, and make sure that they are installed straight, and not hung up in the assembly. Also, make sure that there are no steps or grooves worn into the sliding surfaces of the carrier that the pad could possibly be hanging up in.
*Check to make sure that the caliper bleeder valves are pointing up, not down.* Air rises, so you can't bleed air out of the caliper if the bleeders are pointed down. Usually this occurs when the front calipers are replaced. If the bleeders are pointed down, take the calipers off the car, and install them on the opposite sides of the car.....then they will be pointed up, allowing for proper bleeding of the system.
*Check the hoses for visual bulges....*Hoses very rarely are the cause of a soft or low pedal, but a visually damaged hose needs to be replaced. 
If you still haven't figured it out, send me an IM with your phone number and I'll give you a call. 
*Brakes locking up/dragging without pedal application:*
This is easy. First, duplicate the problem. Make the wheels lock up. then pick up one side of the car with a jack, so that you can spin the wheels to quickly determine if they release though the course of these quick tests:
unbolt the master cylinder from the booster, and pull it about 1/4 inch away...check the wheels. If they released, the problem is that the booster pushrod is holding the master cylinder piston slightly depressed into the master, blocking the return port to the reservoir, so as fluid expands with heat, it pushes the pistons out in the calipers rather than expanding into the reservoir. Some booster have adjustable pushrods, in which case, back the pushrod off a couple turns and try it again. If the booster doesn't have an adjustable pushrod, check to make sure that the brake light switch on the pedal is not holding the pedal slightly depressed (adjust the brake light switch), and if not replace the booster.
If the brakes do not release when the master is unbolted from the booster, then loosen the lines to the master. If the brakes release, replace the master, if not.....read on.
If all four wheels are locked up, pic an easy wheel and concentrate on that one for the rest of this procedure, if only one, concentrate on that one.
Find the connection between the hard line and the rubber hose, and loosen it. See if the wheel releases. if it does, there is a restriction between that connection and the master cylinder, determine what lies between and inspect it. If the wheel does not release, go to the caliper or wheel cylinder bleeder valve and open it. If the wheel releases, the hose is constricted and must be replaced. If more than one wheel is affected, check the hoses on all affected wheels. You can remove them and attempt to blow through them....if you can't, replace them.
If the brakes do not release when the bleeder is opened, then there is a mechanical problem with the caliper. It must either be replaced or rebuilt/repaired. If the brakes don't release with the bleeder open, unbolt and pry the caliper off the car. If the wheel still doesn't turn...your on your own. 
If all four hoses are found to be constricted, and the car isn't 20 years old, chances are the fluid was contaminated with something that caused the EDPM rubber of the hoses to expand, in which case every seal, boot, o-ring, etc...in the system should be inspected and replaced as necessary. If contamination has occured, every piece of rubber in the hydraulic system needs to be replaced without question.

Brake pulsations will be discussed tomorrow, I'm tired. 
A couple months later....
*Brake Pulsations....*
....are mostly always the fault of the installer. There, I said it.
...going back to pad and rotor break-in, one of the main objectives is to bring the pads and rotors up to a high temperature so that friction transfer can occur. Brake pads against bare cast iron don't do much, (unless you're using hawk blues), so during break-in, the pads must transfer a thin and even layer of friction material to the surface of the brake rotor. Then you have 2 like friction materials pressed up against each other, constantly braking and recreating bonds that allow friction to be created between the pads and the rotor.
#1 cause of brake pulsations immediately after installation: coming to a complete stop while the pads are still smokin' hot during break-in, and keeping your foot hard on the pedal. This will cause excessive friction transfer to occur in the spot where the pads came to rest on the brake rotor, thus making that one spot a bit thicker than the rest of the rotor. Every time, from this point on, that this spot on the rotor passes between the pads during brake application, the piston will be pushed back into the caliper a couple thousandths of an inch, which will push fluid back into the master cylinder and cause your pedal vibration.
#1 cause of brake pulsations in 3-10K miles after installation: The installer never checked for runout in the new rotor after installation. Its very common for runout to present in a new rotor that is installed on the hub....even if the rotor is perfect when measured in a fixture, off the car. Say the hub is 5" around, and the rotor is 12" around, 0.001" of runout in the hub will turn into 0.002 or 0.003" of runout in the rotor. Any rust or dirt or even erosion after rust has been cleaned off of the hub can contribute to rotor runout. Some new rotor may have a small amount of runout machined into them due to manufacturing tolerances, which can work to your advantage. On a five lug hub, there are 5 position in which the rotor can be installed. Many times you can "phase match" the rotor to the hub to end up with ZERO runout, which is the ultimate objective. Try all 5 positions until the rotor runout cancels out the hub runout. I like to use a thin layer of high temp grease, or even spray paint the hub and inside of the rotor and button everything up before the paint dries to seal the mating surfaces and prevent rust from forming in the future and jacking the rotor off of the hub creating a runout condition. 
A runout condition will not cause a brake pulsation, because the caliper will simply float back and forth and follow the rotor....with no hydraulic feedback into the master. Over time though, since there will be a couple high spots on the rotor that contact the pads harder and more often than the rest of the rotor, excessive friction transfer will build up on these high spots resulting in Disc Thickness Variation (DTV), which WILL cause a pulsation due to the piston being pushed into the caliper and allowed to come back out at least once per revolution of the rotor. 
Most installers never check runout on new rotor because of time constraints. 
*MACHINING ROTORS:*
There is only 2 right ways to do it....
#1, use an on-car brake lathe. This machines the rotor while it is on the car, mounted to the hub in the position that it will be when in service, so regardless of hub runout or rotor runout, if done properly, the result will be a rotor with ZERO runout. 
#2, if using a bench lathe, rotor runout needs to measures before the rotor is removed from the car. The high spot, low spot, and amount of runout, and position on the hub needs to be marked on the rotor. When the rotor is chucked up on the lathe, before the assembly is tightened down on the arbor, a dial indicator must be used to verify that the rotor has been chucked up with the exact same runout in the exact same spots as when the rotor was on the hub. You can tap the rotor around with a hammer to move it slightly in the cones or chuck on the lathe to change runout. Only after the on-car conditions have been duplicated can the rotor be machined. The rotor must be installed back on the car in the same position from which it was removed, and then runout verified once again. If the result is not ZERO, a mistake was made somewhere. 
Generally, runout of .002" or less is acceptable.
_Modified by machschnelGTI at 6:22 AM 7-24-2007_
_Modified by machschnelGTI at 6:23 AM 7-24-2007_
EDIT: Tried to add some formatting to help read-a-bility.


_Modified by eggroller at 9:19 AM 10-29-2007_


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## jetta86gl (Oct 9, 2001)

*Re: Brake System Diagnosis (machschnelGTI)*

Great post......I'm looking forward to what you have to say about brake pulsations. When I apply the brakes on my '89 jetta it slows down with what seems to be a 'pulse' for a lack of a better description. I did some looking and I'm pretty sure my jetta doesn't have ABS.
I was thinking along the lines that it might be a warped front rotor but if you've got other ideas, I'm looking forward to hearing what you have to say.
Cheers.


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## phatvw (Aug 29, 2001)

*Re: Brake System Diagnosis (machschnelGTI)*

Very nice write up. Just needs some fancy bullet formatting to make it easier to read on screen. Keep adding stuff!

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


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## Banditt007 (Oct 23, 2002)

*Re: Brake System Diagnosis (phatvw)*

def a great post.
Unfortunatly i've been having all sorts of braking issues w/ the mk2...got to slooooowly figgure them all out.


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## machschnelGTI (Jun 28, 2004)

*Re: Brake System Diagnosis (Banditt007)*

I'll continue it the mods make it a sticky. I don't want to invest a bunch of time in this if it will disappear in a couple weeks


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## benA (Feb 23, 2007)

*Re: Brake System Diagnosis (machschnelGTI)*








I need information about high performance brakes. I have one, just bought through the net a few weeks ago. I'm not so familiar with it, maybe you can give me some details about it...


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## MK2 2.0 (Nov 10, 2006)

*Re: Brake System Diagnosis (benA)*

I made my rear disks swap on a mk2 jetta. 
I had a spongy pedal when bleeding the brakes. 
I clamped the rear rubber hoses and I had stiff pedal. 
I change 3 times the calipers, had spongy pedal ( to the floor ). I changed 3 times the cylinder, same thing.
now I have a mk3 master cylinder, but still have pedal to the floor. I put the rear calipers with bleeders looking down and it was better !? Now I still don't know what to do, my proportioning valve is bypassed, the hoses are in metal. I had a stiff pedal before with my drums ( not working, only front disk were working ) 
And my pushing rod in the master is loose. don't know what else to do
help ?


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## Philbert411 (Mar 31, 2003)

*Re: Brake System Diagnosis (MK2 2.0)*

Great info! 
I'm going to have to try this, my brakes seem to be dragging


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## dadsgeoisingilroy (Mar 23, 2007)

*Re: Brake System Diagnosis (machschnelGTI)*

great post patty....if it don't work out there, defenitly midas will hire you. http://****************.com/smile/emthup.gif


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## Philbert411 (Mar 31, 2003)

*Re: Brake System Diagnosis (dadsgeoisingilroy)*

again.. I HAVE to bump this!!!
not only did it direct me to the wrong master cylinder that was installed, it had also clued me in to a bad booster!


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## machschnelGTI (Jun 28, 2004)

*Re: Brake System Diagnosis (dadsgeoisingilroy)*


_Quote, originally posted by *dadsgeoisingilroy* »_great post patty....if it don't work out there, defenitly midas will hire you. http://****************.com/smile/emthup.gif









Rabbit boy thinks he's funny


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## VWsEatRice (Jan 13, 2004)

*Re: Brake System Diagnosis (machschnelGTI)*

what about how to pinch off stainless hoses?


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## machschnelGTI (Jun 28, 2004)

*Re: Brake System Diagnosis (VWsEatRice)*


_Quote, originally posted by *VWsEatRice* »_what about how to pinch off stainless hoses?

Can't pinch off stainless. Put your old hoses back on or go buy a set of cheapies.


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## brian1973 (Aug 17, 2007)

*Re: Brake System Diagnosis (machschnelGTI)*

can anyone help me to get abs codes from my mk4 gti glx? 
well i found out. i bought a obd 2 cable and downloaded VAG COM.
now i can read ABS codes.


_Modified by brian1973 at 5:59 PM 10-25-2007_


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## bengone1 (Jun 17, 2003)

*Re: Brake System Diagnosis (brian1973)*

Brian- Try cleaning the metal shavings from your ABS sensors at each wheel. The code should correct itself if it was the problem. I have seen a good power washing get it clean enough.
Just a safety reminder. If there is any rust on the hub or rotor surface remove it or the wheel can and will work itself loose while you are driving as the rust gets rubbed off and the lugbolts are suddenly not so tight. Seen it happen more than once.


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## brian1973 (Aug 17, 2007)

*Re: Brake System Diagnosis (bengone1)*

THANKS, DUDE. I WILL CLEAN THEM AROUND LUNCH TODAY AND TAKE IT FOR A DRIVE. DO YOU HAPPEN TO KNOW IF THE "VAG-COM" CABLES (ON EBAY FOR LIKE $15) CAN BE USED TO READ 
ABS CODES?










_Modified by brian1973 at 7:37 AM 9-3-2007_


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## bengone1 (Jun 17, 2003)

*Re: Brake System Diagnosis (bengone1)*

VAG-COM can diagnose ABS problems. I have no idea what the generic cable you are getting off of Ebay can do much less what you will have to invest to get software.


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## 50buckbunny50 (Jul 24, 2006)

*Re: Brake System diagnosis, no pedal return*

Been having a miserable time with my rabbit gti brakes, a pedal that wouldn't come back up. Checked the pivot on the pedal cluster and there was a lot of friction there. Anytime clutch and brakes were pushed in together the clutch would hold down the brake pedal just slightly, mimicing a stuck caliper or? Anyone seen A1 pedal cluster bushings available? Yet another thing to check in a 23 year old car that has sat for years. Anyone else see this in their old Rabbits?


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## volksrage13 (Oct 22, 2007)

*Re: Brake System diagnosis, no pedal return (50buckbunny50)*

i have a 95 jetta gl, i have the softest sponge of a pedal, and when fully depressed there is no power. when i fully depress my pedal i only have power on my front left rotor. i am a college student and do not have money to go down the line replacing parts.
help....


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## machschnelGTI (Jun 28, 2004)

*Re: Brake System diagnosis, no pedal return (volksrage13)*


_Quote, originally posted by *volksrage13* »_i have a 95 jetta gl, i have the softest sponge of a pedal, and when fully depressed there is no power. when i fully depress my pedal i only have power on my front left rotor. i am a college student and do not have money to go down the line replacing parts.
help....

Well good for you. Why don't you read through this thread then (its free) and then diagnose your problem.


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## brian1973 (Aug 17, 2007)

*Re: Brake System diagnosis, no pedal return (machschnelGTI)*

yeah, a 95 car's brakes arnt that complicated. it should only take some common sense and a repair guide.


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## bange.fur.sie (Aug 10, 2007)

*Re: Brake System Diagnosis (jetta86gl)*


_Quote, originally posted by *jetta86gl* »_Great post......I'm looking forward to what you have to say about brake pulsations. When I apply the brakes on my '89 jetta it slows down with what seems to be a 'pulse' for a lack of a better description. I did some looking and I'm pretty sure my jetta doesn't have ABS.
I was thinking along the lines that it might be a warped front rotor but if you've got other ideas, I'm looking forward to hearing what you have to say.
Cheers.

I agree, nice educational cheers!


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## nduetime (Mar 22, 2003)

*Re: Brake System diagnosis, no pedal return (50buckbunny50)*

I was thinking that they could be found here...http://www.4crawler.com/Diesel/ForSale/ but I just checked and noticed they were the accelerator pedal bushings. I don't know if they would work or not, not even sure what the brake bushing looks like but figured it was worth a look. Sorry-b.


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## briansimons (Oct 8, 2006)

i'm wondering, i just picked up a 91 GTI for CHEAP because it has brake problems, all 4 calipers are new, new brake master cylinder, new proportioning valve, new pressure regulator, and new pads, seems the only things not done yet are lines, and brake booster, they couldn't get the brakes to bleed at all, pedal is pretty soft just about all the way to the floor, they just BARELY work. does this sound like something anyone would know? i haven't even stuck it on the lift yet, all i've done is drove it a quater mile, i'd kinda like to get some insight before i dive in from someone who's smarter than me with brakes...


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## machschnelGTI (Jun 28, 2004)

*Re: (briansimons)*

calipers are on the wrong sides...bleeders pointed down.
Also, disconnect the valve and wire it open when you bleed the rears.


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## dirtymanpon (Jul 22, 2008)

*Re: Brake System Diagnosis (machschnelGTI)*

Bringing this one back. I have a 00 VR6 Jetta. Until recently everything was fine with the brakes. Unfortunately now whenever I slowly brake. Say 3mph or so and am about to fully stop I get this skipping/and groaning coming from the front brakes. It might only be the drivers side but it is hard to tell. So is it a result of hot spots or should I be looking somewhere else? Any help would greatly be appreciated.


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## dirtymanpon (Jul 22, 2008)

*Re: Brake System Diagnosis (dirtymanpon)*

Anyone?


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## HilF (Jan 10, 2004)

*Re: Brake System Diagnosis (dirtymanpon)*

way too vague.
how much meat is left on your pads?
how are the rotors?
does your car see track time?
need way mroe info


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## dirtymanpon (Jul 22, 2008)

*Re: Brake System Diagnosis (white_r!ce)*


_Quote, originally posted by *white_r!ce* »_way too vague.
how much meat is left on your pads?
how are the rotors?
does your car see track time?
need way mroe info


Pads look good. Rotors were replaced 25k ago with the pads. No track time it is my daily.


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## runes52 (Oct 31, 2003)

*Re: Brake System Diagnosis (machschnelGTI)*

I have a problem that I have not seen posted as yet.
I have a 96 Passat TDI. The inner rear brake pad on the left side started dragging.
I was on a 1000 mile road trip, and I ignored the noise (slight), other than jacking up the car and testing the drag, which was moderate. I could tell the outer pad had appropriate clearance, but the inner was dragging. 
On the way home, the pad wore to metal. On a Sunday afternoon in a remote town and 200 miles from home, I was able to find a guy who was able to disable the brake, and I made it home. The outer pad looks nearly new.
The question is: Why is just one pad dragging, engaged, pressing on the rotor, or however it may be described? What must be done to fix it, in addition to new pads and rotor.
Should I replace pads and rotor on both sides at once?
Thanks.


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## iamnobody1 (Oct 15, 2008)

*Re: Brake System Diagnosis (runes52)*

rear caliper is not self-centering
most probable cause corrosion induced piston drag/seizure followed by mech parking brake not retracting @ caliper
rear caliper is combined service caliper incorporating mechanical parking brake
best advice/lowest total cost of repair - replace both rear calipers now and also clean/re-grease (2) guide pins each caliper
edit single malt induced keyboard failure


_Modified by iamnobody1 at 6:30 PM 10-20-2008_


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## runes52 (Oct 31, 2003)

*Re: Brake System Diagnosis (iamnobody1)*

Thanks. I had a complete brake job done.


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## 92mkII (Jan 11, 2008)

*Re: Brake System Diagnosis (runes52)*

Wow am I glad I stumbled on this. My brakes were kinda bad, but suddenly went out to the point of almost no pressure at the pedal and barely being able to stop. I've done some brake work in the past, pads, rotors, calipers, bleeding, but was baffled by this one. Now I'm looking forward to getting out there tomorrow with my new-found knowledge and trying to figure this out. Thanks so much. If I have any more problems figuring it out, I'll be in touch.


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## Fastboy501 (Aug 28, 2006)

so if i have the Brake Pulsations, should i resurface the rotors and or replace the pads? i just had stainless lines installed and a brake system flush with dot 4 blue fluid. thought it would fix the problem. the car has a firm pedal feel but doesnt have any harsh initial bite when slamming on the brakes, even with the hawk hps pads heated up on the brembo slotted rotors. do i need new pads and a resurfacing? the pedal does click sometimes and i dont think its the abs system. after reading this thread, sounds like ive got a hot spot that makes the piston in the caliper hop. any help would be greatly appreciated. thanks!


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## rsalazar22 (Jun 20, 2008)

*Re: Brake System Diagnosis (machschnelGTI)*

so i bought a 85 gti last week and been workin on it. the thing runs like a beast, its only the 1.8, bu the brakes have been givin me hell. ive replace the master cylinder blead all lines and calipers made sure the calipers werent seezed and the brakes still arent workin right. the pedal is mush and the stoppin is really delayed. ive traced the lines and it seems that its missing a porportioning valve at least compared to the jetta i had and the golf at the junk yard. it has the pressure spring valve on the driver side by the rear axle but the one that is about a foot away in the line from the master cylinder the one by the front axel isnt there its just straight line. according to the all the books i have read there has to be a porportioning valve. tell me if im wrong or if i have to run new lines with a valve there
help me out man


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## Andrizzanizz (May 18, 2009)

I have been trying to locate these "line locks" or brake clamps.
i have called and looked at every local parts store around me and all i could find was a part for a mustang that was 123. I even looked on the internet and had no luck. can anybody point me in the right direction as to where i can acquire one of these.

And also just to see if you guys can help me diagnose my brake problems, i own a 90 mk2 golf. I swapped in a aba 2.0 from a jetta and i put a t04e turbo on it. After i was done i went to press the brakes and it basically had no pressure till it was almost on the ground. i saw a brake line on the fire wall that i think can be the culprit, because it was by where i put the turbo. but idk. i checked to see if theres any leaks and theres none. i filled up the mc. and bleed the two front brakes and it just kept spitting fluid and the pedal never increased in pressure.
anybody have any ideas?


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## elio (Nov 15, 2006)

*Re: Brake System Diagnosis (machschnelGTI)*

Hi machschnelGTI, I send you a question here to look for some advice.
Friend I have been looking around and searching about an issue that I have with my brakes. You can lookk my questions here in the forums, look here -- http://forums.vwvortex.com/zerothread?id=4482141.
The car is breaking quite good but with a little more pedal travel and a little soft pedal than it was before changing, rotors, pads, front caliper metal bushings, ss lines and fluid.
I have bleed my brakes twice, and last one I cycle the ABS module just after bleed the brakes without opening any bleeder. 
I have follow this steps, http://www.ross-tech.com/vag-c....html, after bleeding the brakes to cycle the abs module and my brake pedal issue still remains.
Then my question is, from your point of view and experience, the problem is more related to air in the system than any other thing? do you think that is some air still in lines or abs module?
Thanks in advance for your support.


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## elio (Nov 15, 2006)

*Re: Brake System Diagnosis (elio)*


_Quote, originally posted by *elio* »_Hi machschnelGTI, I send you a question here to look for some advice.
Friend I have been looking around and searching about an issue that I have with my brakes. You can lookk my questions here in the forums, look here -- http://forums.vwvortex.com/zerothread?id=4482141.
The car is breaking quite good but with a little more pedal travel and a little soft pedal than it was before changing, rotors, pads, front caliper metal bushings, ss lines and fluid.
I have bleed my brakes twice, and last one I cycle the ABS module just after bleed the brakes without opening any bleeder. 
I have follow this steps, http://www.ross-tech.com/vag-c....html, after bleeding the brakes to cycle the abs module and my brake pedal issue still remains.
Then my question is, from your point of view and experience, the problem is more related to air in the system than any other thing? do you think that is some air still in lines or abs module?
Thanks in advance for your support.


Any ideas or comments friends????


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## elio (Nov 15, 2006)

*Re: Brake System Diagnosis (elio)*


_Quote, originally posted by *elio* »_
Any ideas or comments friends????

Nobody have an idea???????????


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## mendonik (Aug 12, 2009)

*88 Jetta weak brakes*

My stock 88 Jetta GL has weak braking power. Even a hard application of the pedal will not skid any tires on dry pavement. It has been this way for years. The vacuum servo works. The pedal is not spongy. There's plenty of meat on the rotors. There are drum brakes on the rears.
I'm wondering if the weak stopping power is due to bad choice of brake pad material. Or possibly it's because I replaced the proportioning valve and may not have adjusted it correctly. 
Anybody got an informed opinion or suggestion? Where can I find info about relative stopping power of different friction materials?
When I look at available replacement pads I see different choices of pad material: organic, semi-metallic, metallic, ceramic. Does the choice of material affect the friction? I'm not so concerned with how long they last, just how well they stop the car.


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## filmnoire (Sep 11, 2009)

*Re: Brake System Diagnosis (machschnelGTI)*

Hey, great write up. I've been having intermittent ABS light occurrences and occassional total pedal failure. I'll use your write up as a guide to test the MC and wheel cylinders before assuming the worst (ABS Module). Thanks!








-C


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## DAVEG (Aug 14, 2001)

Mach,

Glad to see such good information...I (shop) replaced all of my brakes (84 GTI) with factory rebuilt F calipers 10.1 Scirroco on front and R discs from Scirroco also new MC, pedal cluster, proportioning valves and SS lines. Everything seemed good untill about 10 miles of driving and the brakes started dragging. The problem seemed to get better after letting the car rest and driving a little but it is definately dragging...won't coast and can't push it. I think it is the RF wheel.

Is this the caliper or MC? New MC rebuilt Caliper. Is a simple brake piston rod adjustment all that is needed? I hope.


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