New member with ABS issues

[teng3 0]

Hi, i'm a new Corrado VR6 owner from the states. I bought it dirt cheap and am working like crazy to make it road worthy. Issues when purchased: Passenger door handle, sun roof, heater core, radiator fan, major coolant leak, no brakes, spoiler, a tail light, fog lights cracked, no antenna, and a few dings here and there. Sounds like a lot, but i've managed to fix the door handle, radiator fan (bad harness) coolant leak, spoiler, and tail lights for close to nothing, thanks to a donor car. Right now, my biggest concern and what's holding me from putting the car on the road is brakes.

 

The symptoms are: Between key in, on -> start -> on position, the emergency brake light indicator never turns off, handbrake up or down, and the ABS light never comes on, ever. The brake pedals are very firm, it takes a LOT of effort to stop the car, and the pump under the brake fluid reservoir doesn't seem to come on during ignition.

 

Things i've checked: Brake pad wear, brake fluid level, fuse panel for broken fuses, and i've replaced the abs/emergency brake warning indicator. Everything was in check. I then went ahead and replaced the abs and hydralic pump relays (79 & 178) and checked their related 30amp fuses. Still no difference. Personally, I still believe it's an electrical issue because the ABS light isn't even coming on. I have a service manual, but I don't have diagnostic tools... The next step that was recommended that I checked was the abs control unit. Unfortunately, I don't know where it is. I was told it should be right above the hood release lever above the driver side kick panel. When I looked, what I saw on the left of the instrument cluster was this:

 

It looks as if something should be sitting on that bracket. Then I looked to the right of the instrument cluster (cluster removed) and noticed two sealed boxes back to back.

 

I believe one of those is supposed to be cruise control? But what is the other for? Finally, I was suspicious of the lonely bracket when I found a picture of an ABS control unit on ebay that looked like this:

 

 

Coincidentally, the two prongs on the control unit look like they would match up with the brackets in the first picture very well. Also, I found a fairly large dangling wire harness next to that bracket. Am I on to something? Am I missing a control unit and maybe thats why there's no activity going on? I don't know how different european spec corrados are but hopefully, not too much.

 

If no one has any idea what's going on, perhaps someone could tell me how to by-pass the abs and just ignore the whole system all together. Does traction control work in conjunction with abs and would that be affected?

 

Sorry for such a long post, I just want to be very thorough and not waste time going back and forth trying to fill in the details. Thanks for any help that can be provided.

 

~Tim

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[dr_mat 0]

First off - great posting - as you say, best to include everything up front, rather than have to answer 20 questions before people understand your question! :)

 

Second, since you're LHD, the "pump under the brake fluid reservoir" is the ABS pump and valve block unit. If this never primes, and your ABS light never comes on on the dash, chances are you've an electrical problem with those circuits. There's a separate relay for the ABS pump and for the control unit - you'll need to check both.

 

The very hard pedal *shouldn't* be effected by the faulty ABS, so it sounds like you've no vacuum assist, so you want to be looking for vacuum lines from the engine manifold to the brake servo unit (sorry I don't have a clue where it's routed!). Chances are it's broken or you have a duff brake servo unit.

 

FYI the ABS control unit is made by Teves, so if that box has Teves logos all over it, you've hit the right bit and you want to start looking for a valid 12V supply on the power lines in the big connector it attaches to. Again, sorry I can't give you any more specifics...

 

Yes, traction control is handled by the same units as the ABS, tho most people agree it's next to useless anyway, so you won't miss it.

 

But like I say, the ABS failure should NOT effect the pedal force requirement, so you should be able to get the brakes working better without having to fix it!

[Scott 0]

The ABS and EDL systems work together. It sounds to me as though you have a missing ABS unit! :shock:

 

Either way even so the brake system is designed so that if the ABS should fail then the brakes will still work perfectly but without the ABS obviously...

 

So I would suggest looking at these areas:

 

Slave Cylinder

Master Cylinder

Calipers

 

From what you say about it taking alot of effort for the brakes to work I would suggest the Master Cylinder being the culprit.....

 

With engine off...

 

Pump the brake pedal until its rock hard.

 

Keep foot applied on brake.... start car... does the pedal sink about half and inch to an inch?

 

If so your master cylinder is fine.... if not then its time for a new one...

 

I hope that helps!

 

Cheers

 

Scott

[teng3 0]

I was also wondering about that. I've seen plenty of cars with bad abs units stop just as easily as cars with good abs units. So now that you've brought up these potential culprits, i'm thinking, one of these is the reason the idiot light (e-brake) stays on constantly. I've tried previously to start the car with the foot on the brake, and yes, I have noticed that the pedal doesn't move any after the car is started. So now, I have a potential master brake cylinder issue huh? Does anyone know if a 92' Passat VR6 would have a compatible master brake assembly? I have a donor car sitting in my yard. Also, does anyone think that possibly, because the mbc is out, that is why the abs light doesn't come on at all and the pump doesn't bother coming on? If the brakes dont work, disable abs? Make sense? If the passat can be a donor, i'll replace it tonight. Thanks again and for a quick response.

 

~Tim

[dr_mat 0]

Good question - not sure what the potential implications are of trying to run the ABS pump on a car with no fluid, maybe there's a safety cut-out.

Yeah, sounds like your master cylinder is messed up...

Dunno about the Passat VR6 tho, compare the part numbers!!

[Henny 0]

I may be wrong on this, but don't the American Corrados not have a brake servo due to being Left Hand Drive? If I remember correctly, the ABS pump does the same job as the servo, so if you're missing the ECU, and the pump is never firing, you're getting NO assistance on your brakes hence the heavy/solid pedal...

 

If the ABS ECU was missing, you'd also get all sorts of oddities with brake warning lamps and ABS lights as I'm pretty sure the level warning lamp is illuminated by the ABS ECU...

 

I'm not sure if you CAN disable the ABS on a LHD car without loosing the brake assistance due to not having a servo... I think your only choice is to get hold of an ABS brain and see if it works with that... (see if ya can borrow one from someone in a local VW club?)

 

Hope this makes sense, and please tell me if I'm wrong about the servo 'cos, as I say, I could be talking utter pish if I've remembered incorrectly.... 8)

 

Oh, and Welcome to the forum... It's always nice to get some more international members on here... 8)

[teng3 0]

Yes Henny, you're right. I checked the service manual and others have agreed, there is no brake booster/servo. Without an ABS hydralic pump, I have no assist. Further forum hopping suggests I really am missing the control unit for the abs. I've just purchased an OBD I scanner in hopes of finding out specifically what is wrong but now that I think about it.... doesn't the abs control unit need to be present in order to report DTC's to my scanner?

[Henny 0]

yup... without the ABS brain, the scanner has nothing to talk to... :|

 

Looks like it's time to try and find yourself a brain, Mr.Scarecrow... ;) :lol: [/wizard of oz]

[teng3 0]

ok, found the brain. Are there any electrical tests I can do on the unit itself? How about the harness. I'll do an OBD scan on Friday when I get my scanner in the mail. I know I need to check the power line and make sure i'm getting atleast 10.5V and check the grounds, but what else?

[Henny 0]

Personally, I'd just plug it in and see what happens... but that's just my way! ;) :lol:

 

From your photos it doesn't look like the wiring's been damaged, just that the brain was missing... :?

[teng3 0]

no no, the control unit was found, in it's correct place, and connected. The pics I took were of where I thought the unit would be. After more ripping, I finally found it.

[Henny 0]

oh.... :?

 

Erm... odd... wait until the OBD scan and see what codes it throws at you in that case... :|

[teng3 0]

Alrighty, here are, from my memory, the scan results. No engine code reports at all. Most of the inlet and outlet abs valves are faulty. The main ABS valve is faulty. A few sensors are faulty (dirty). From what I can evaluate, none of that equates to why my abs system is dead. My justification is that my sister's corrado had virtually all of the same error codes and her boyfriends Passat has lots of them too but their brakes operate normally (Haven't tested actual ABS functions but pedal effort is normal). Their ABS warning light operates normally (on for 15-60 seconds, then off). Also, I did perform most of the electrical tests in the Bentley manual for the control unit. Supply voltages are all good. Grounds are good. The hydralic pump relay is good. Things that went bad.... most of the inlet and outlet abs valves. Resistance was spec'd around 1.5 to 50 ohms for various terminals but I got shorts on almost all of them. Again, i'm sure it's directly related to all of the error codes coming up, but I don't think they're essential for pump operation, as my sister has the same issues. Finally, looking more through the bentley manual, I saw that the Pressure warning switch was an easy replacement. I'm suprised no one mentioned it, but apparently, that tells the pump to turn on and off. If it's faulty, that could be a very good reason for why the Hydralic pump doesn't kick in. I'm going to rip one out of my "Parts" passat and see if it helps out. If not, I plan on replacing the entire abs system with the "parts" passat one. I'm getting desperate. I've priced out the ABS control Unit at $680USD and the hydralic pump at $1200USD!!! There's no way i'm paying as much for a pump as I did for the whole car itself! Heh, what do you think about plan of actions?

[dr_mat 0]

Sounds like a good plan!

 

Can you clear all your error codes and try again? If they all come back, you have a very sick ABS pump unit, OR you have very bad connections to the ABS controller, causing it to think that everything else is knackered.

 

If so many valves have gone in the pump, that sounds almost like it's had bad fluid put through it or something?

[Henny 0]

with you on that one dr_mat... see what happens if you clear the memory after changing that switch... I don't know too much about the ABS pump itself, it's an area I've (thankfully [touch wood] ) never had go wrong on my car, so I've yet to learn about it in depth, but there's people here who have gone in a bit deeper who may be able to help... 8)

[Bruno 4]

I'm going to rip one out of my "Parts" passat and see if it helps out. If not, I plan on replacing the entire abs system with the "parts" passat one. I'm getting desperate.

 

Its a very different setup to the UK system, hence the fault sequence is different. I'd go straight to the Passat's system. It really should be totally interchangeable. The key to your problem is in that hard pedal. The pressure is up but its not being gated. Hence could be the valves not sending their closure signal to the brain.

 

Do ensure that before you move anything, please make sure that the pressure dome is allowed to empty out gently first..... thats if you prefer going thru life in 1 piece.

Best of luck.

[teng3 0]

doods!!! :lol: I replaced the entire abs system and upon turning the ignition key, the pump pressurized!!! Soooooo, i have brakes. Hooray, in any case, i've got a bunch of tiny issues now. The brake light goes out after dropping the hand brake now, ABS light still NEVER comes on. Speed sensors must be dirty as per error codes so the wheels can be locked up on dirt roads currently. The right rear hub is near frozen (can't turn hub by hand). Not sure if that's hand brake related or caliper seizing related. Either way, my car is road worthy!!!

 

So in conclusion, my abs problem was directly related to either, a faulty $1200usd hydralic pump, or a $225usd pressure warning switch. I'm happy, and thanks to all that contributed. Much appreciation. =)

[G60Jet 1]

LHD Cs with abs have no servo, the pedal connects straight to the ABS pump. If you need and LHDS pics let me know, I´ll be happy to help.