deveous9 New Reader
Oct. 5, 2011 3:33 p.m.

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.

AngryCorvair SuperDork
Oct. 5, 2011 3:42 p.m.

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.

deveous9 New Reader
Oct. 5, 2011 3:52 p.m.

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.

92CelicaHalfTrac SuperDork
Oct. 5, 2011 4:09 p.m.

Sounds more like.... anything BUT the ABS unit.

Cone_Junky HalfDork
Oct. 5, 2011 4:36 p.m.

It does sound more like a booster issue.

VWguyBruce HalfDork
Oct. 5, 2011 7:58 p.m.

Check to see if the booster is filled with fluid!

deveous9 Reader
Oct. 6, 2011 1:59 p.m.

has anyone remoed the abs unit and hav had success with braking???? using an older model as a transplant vehicle?? someone help!!

AngryCorvair SuperDork
Oct. 6, 2011 3:48 p.m.
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.

noddaz New Reader
Oct. 6, 2011 3:58 p.m.

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...

deveous9 Reader
Oct. 7, 2011 9:32 a.m.

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...

mad_machine SuperDork
Oct. 7, 2011 9:38 a.m.

It has a booster of some sort.. probably hydraulic like a Classic Saab 900.

RossD SuperDork
Oct. 7, 2011 10:16 a.m.

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.

rodrammage New Reader
Oct. 7, 2011 11:12 a.m.

In reply to deveous9:

You have a faulty bomb. Replace it or replace your shop.

pigeon Dork
Oct. 7, 2011 11:20 a.m.
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.

wclark New Reader
Oct. 7, 2011 12:14 p.m.

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.

16vCorey SuperDork
Oct. 7, 2011 2:45 p.m.
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.

wclark New Reader
Oct. 7, 2011 4:29 p.m.
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.

deveous9 Reader
Oct. 12, 2011 8:30 a.m.

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.

RossD SuperDork
Oct. 12, 2011 9:05 a.m.

I am sorry for your loss of a lot of beer money.

SlickDizzy SuperDork
Oct. 12, 2011 9:37 a.m.
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...

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