Just purchased me a 1991 VW Jetta GLI 2.0 DOHC 5 speed and super clean. 
Only problem is that the abs unit is bad. 
And when i say bad i mean that it takes tons of leg power to make it stop!! Now my shop is unable to source a replacement. I guess rebuilding it is not an option either. Is removing the abs system completely an option??? Lets hear it from the pros, can i remove the abs unit i this model car? Any and all help is greatly needed.
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Oct. 5, 2011 3:33 p.m. deveous9 New Reader
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Oct. 5, 2011 3:42 p.m. AngryCorvair SuperDork
explain to me how
"it takes tons of leg power to stop" = "the abs unit is bad"
because i've only been an ABS development engineer for the last 18 years and i can't make that jump.
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Oct. 5, 2011 3:52 p.m. deveous9 New Reader
Well the car is in the shop right now and they explained to me that the abs unit is faulty. Something about not being able to read the unit and it not responding the way it should. All they said was that i need a replacement unit.
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Oct. 5, 2011 4:09 p.m. 92CelicaHalfTrac SuperDork
Sounds more like.... anything BUT the ABS unit.
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Oct. 5, 2011 4:36 p.m. Cone_Junky HalfDork
It does sound more like a booster issue.
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Oct. 5, 2011 7:58 p.m. VWguyBruce HalfDork
Check to see if the booster is filled with fluid!
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Oct. 6, 2011 1:59 p.m. deveous9 Reader
has anyone remoed the abs unit and hav had success with braking???? using an older model as a transplant vehicle?? someone help!!
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Oct. 6, 2011 3:15 p.m. Datsun1500 SuperDork
We are trying to help. We are doing that by telling you the ABS is not what the problem is. I will answer it anyway:
All brake systems are basically the same since about 1920ish. The pedal connects to a rod that pushes on the master cylinder which causes fluid in the lines to push on the pad/shoe. It is the same exact system still. There have been some improvements. Putting a booster on the system made it easier to push the pedal (power brakes). Putting an ABS module in the system made it possible to not lock the system.
You can take out the ABS module and run new lines and have regular power brakes (as in a 1985 car). You can take out or unhook the booster and have regular brakes (as in a 1965 car). Either way you will have brakes. Ones than can lock up (no abs) or ones that are hard to push (no power brakes). There are millions of cars without either that stop fine.
If you take out the ABS module and run the lines direct you will have a car that does not have abs. This means you can lock the brakes up. It does not mean the pedal is tough to push.
You have a power brake issue, not an ABS issue. Have the shop run new brake lines (bypassing the abs) and when it is still hard to push ask how it is an abs issue when there is no abs on the car. It is the same as saying a 1985 Fiero has an ABS issue because the pedal is hard to push, the car does not have abs so it must be something different....
If you had an 85 Fiero and not an 01 Jetta with a hard to push pedal, what would you think the cause was?
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Oct. 6, 2011 3:48 p.m. AngryCorvair SuperDork
deveous9 wrote:
Well the car is in the shop right now and they explained to me that the abs unit is faulty. Something about not being able to read the unit and it not responding the way it should. All they said was that i need a replacement unit.
i think you should replace your shop.
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Oct. 6, 2011 3:58 p.m. noddaz New Reader
Ok did a little digging on this and it seems that the car does not have a brake booster like a regular car... That is if I am reading the picture correctly... It wouldn't be impossible to retro fit regular brakes... but it would time consuming...
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Oct. 7, 2011 9:32 a.m. deveous9 Reader
In reply to noddaz: Yea you are correct, the 1991 jetta gli did not come with a booster. It did however run a master cylinder which is connected to the abs unit. And it seems that my shop is not willing to do the non-abs swap. I will look for a new shop once this issue is resolved. I found a place in orange county that rebuilds abs units and it going to cost me 550 bucks!!! Then i still have to pay my shop to do the install work plus bleeding of the lines, etc...
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Oct. 7, 2011 9:38 a.m. mad_machine SuperDork
It has a booster of some sort.. probably hydraulic like a Classic Saab 900.
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Oct. 7, 2011 10:16 a.m. RossD SuperDork
I had the exact car you have now, '91 Jetta GLI. When I sold it to a self proclaimed "VDub Guy" he said the first thing he was going to do was to pull off the electronic brakes. I didn't really care at the time what he was talking about; I was too excited to have money in college.
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Oct. 7, 2011 11:12 a.m. rodrammage New Reader
In reply to deveous9:
You have a faulty bomb. Replace it or replace your shop.
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Oct. 7, 2011 11:20 a.m. pigeon Dork
rodrammage wrote:
In reply to deveous9:
You have a faulty bomb. Replace it or replace your shop.
To be more clear, the large bomb-like item next to #11 is a pressure accumulator - see the hose #13 that feeds into master? That's your brake assist system - when the "bomb" fails you lost braking assist and get a hard to push pedal. ABS should have nothing to do with this.
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Oct. 7, 2011 12:14 p.m. wclark New Reader
In reply to deveous9:
Ignore all the above. Your brake system is not like what everyone seems to assume. You do not have a master cylinder, you have a brake modulator controlled by the pedal. You do not have a booster because the fluid is pressurized to about 200Bar by that motor in the drawing, held in that accumulator and released by the motion of your pedal through the modulator. The ABS part is in the modulator and controlled by an electronic controller. If the fluid pressure drops to around 0, the pedal resistance increases dramatically because you are now operating the modulator in a mode something akin to a master cylinder - all brake pressure is developed by your pedal pressure - but it is only intended as a fail-safe and is not very efficient.
You may replace the whole shebang with a non ABS system by installing a standard VW vacuum booster, master cylinder, rear brake pressure reducers, and mounting hardware from non-ABS A2 chassis cars and with suitable changes to the brake lines to reach the new master cylinder.
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Oct. 7, 2011 2:45 p.m. 16vCorey SuperDork
wclark wrote:
In reply to deveous9:
Ignore all the above. Your brake system is not like what everyone seems to assume. You do not have a master cylinder, you have a brake modulator controlled by the pedal. You do not have a booster because the fluid is pressurized to about 200Bar by that motor in the drawing, held in that accumulator and released by the motion of your pedal through the modulator. The ABS part is in the modulator and controlled by an electronic controller. If the fluid pressure drops to around 0, the pedal resistance increases dramatically because you are now operating the modulator in a mode something akin to a master cylinder - all brake pressure is developed by your pedal pressure - but it is only intended as a fail-safe and is not very efficient.
You may replace the whole shebang with a non ABS system by installing a standard VW vacuum booster, master cylinder, rear brake pressure reducers, and mounting hardware from non-ABS A2 chassis cars and with suitable changes to the brake lines to reach the new master cylinder.
Did you read the above? If so, you'd realize that most of the people that replied know exactly what kind of brake system it has, and even posted a freakin' diagram.
But yes, you can replace the ABS assembly with a traditional master cylinder and brake booster, lines, etc. Or you can replace the pressure accumulator. Either one will fix it, and it's a pretty easy job either way.
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Oct. 7, 2011 4:29 p.m. wclark New Reader
16vCorey wrote:
Did you read the above? If so, you'd realize that most of the people that replied know exactly what kind of brake system it has, and even posted a freakin' diagram.
But yes, you can replace the ABS assembly with a traditional master cylinder and brake booster, lines, etc. Or you can replace the pressure accumulator. Either one will fix it, and it's a pretty easy job either way.
You are correct. I am sorry. I should not have said ignore all.
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Oct. 12, 2011 8:30 a.m. deveous9 Reader
Thank you everyone who shared but my final option was to get the abs unit rebuilt for a fee of 550 bucks! I was only able to find one shop that rebuilds those units.
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Oct. 12, 2011 9:05 a.m. RossD SuperDork
I am sorry for your loss of a lot of beer money.
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Oct. 12, 2011 9:37 a.m. SlickDizzy SuperDork
deveous9 wrote:
Thank you everyone who shared but my final option was to get the abs unit rebuilt for a fee of 550 bucks! I was only able to find one shop that rebuilds those units.
Dayum! Wish I had seen this thread earlier. As noted, all you needed was a pressure accumulator/"brake bomb." You could have saved a hell of a lot of money...I have a '92 that I just sorted all the brake issues on for my girlfriend...
