G60 Front Brake Problem!!!

[Topaz2008 0]

My car has been in storage all winter and during this time I have been working through a long list of things including the braking system. I have replaced all my flexible hoses with the Goodrich braided type, changed the brake fluid (using a pressure bleed) and fitted new disks/pads/bearings at the back (the fronts were done in the summer). Yesterday I took the car out of storage to clean it ready for driving on Friday (1st of the month).

 

The front brakes seemed to be binding (jacked the car up and could not turn the wheel) :( so I stripped and cleaned both sides and wound the calipers back. All seamed fine :shrug: and on testing the car again a similar thing happened :mad2: . I noticed before the car went into store that the ABS sometimes cut in on firm braking (not hard) and occasionally I would hear the ABS run for a few seconds while driving :scratch:

 

Could the ABS unit cause the front brakes to stick if one of its internal valves had stuck?

Could it be air in the ABS unit?

Does anyone have any other suggestions? :mad2:

[Topaz2008 0]

BUMP.... Anyone could do with some help here :?

[Topaz2008 0]

BUMP AGAIN

[StuartFZR400 0]

Right, I doubt the ABS will do that. Make sure those slots in the abs-wheel are clear. I presumethe abs head/sensor is ok too; try not to knock it when taking stuff on/off.

 

Im puzzled as to why the abs would be coming on during normal driving too; so indicates a problem. However, you mention under braking too; were you braking a little hard really, or was it close to winter and slippy? Are your tyres naff? Any locking up and the abs will kick in.

 

You say the brakes seem to be binding, but you cannot source. Can you list what you checked?

I'd go for: piston moves well and is not rusted; then calipers slide well on the pins into the carrier, checking the tiny rubber boots are not cracked; then ensure the pads are not sticking on, which can be cause by clogged or rusty surfaces on the caliper - see where the pads should slide on those flat spots, they need to be squeaky clean. Sounds like something has ceased. You also want equal pressure to both sides - i'll think of how to check that when time allows, or someone beats me to it; maybe an extra pair of eyes will help.

[Topaz2008 0]

Thanks fro the reply Stuart :D . Please see below for details of work carried out and checks made:-

 

Front Brakes

 

1. I have taken apart both front caliper sets and wound the pistons in. The passenger side was a little harder to do than the drivers but I put that down to the fact that it is further away from the master cylinder. (Both seamed the same as other cars I have worked on)

2. The rubber boots are fine and the pins move easily.

3. The pads fit perfectly in the caliper.

4. Its all clean and free from rust etc.

5. All parts have only covered 1000 miles (motorway running in new engine)

6. ABS sensor and slotted rings are spotless and connections are clean

 

Rear brakes (no issues)

 

1. New disks pads and bearings

2. Reused slotted rings but cleaned well with a wire brush.

 

I bought the car home from where it has been in store over winter. The front brakes were dragging when I set off and after approx 6 miles I pulled over to let them cool down. Whilst driving at speeds between 20 and 50 MPH I could occasionally here the ABS pump buzzing for the occasional 2-3 second period but not applying the brakes. When I pulled up just normally I could fell the ABS trying to cut in (kicking the pedal). This was normally shortly before the car came to a halt (this was gentle "like my mum drives" braking :lol: ).

 

I was speaking to my Brother on the phone who was googleing the symptoms (without much luck) and from what we could work out the Corrado use's the ABS pump to assist the braking instead of a servo. As an experiment I unplugged both the ABS ECU and the ABS pump. The car drove the same but without the pump buzzing. It was a hell of a journey home and it took me 3 hours to cover the last 12 miles as the Police had closed the road due to an accident and at 2 MPH you don't really need brakes to stop when there dragging! Just take your foot off the gas and it stops on its own.

 

Right I finally made it home and have plugged the ABS pump back in again (not the ECU) and taken the car for a drive. When I first started the car there was a small buzz from the ABS pump and hey presto all the brake binding issues have gone away. I can jack each front wheel and the wheels will spin by hand (before I could not turn them)

 

PS tyres are nearly new too + ABS light comes on when ignition is switched on then turns off as it should

 

I can only conclude that this is something to do with either the ECU or the ABS pump (ECU or signal to ECU as its unplugged and problem has gone maybe?) but not understanding how the pump doubles up as an ABS system I am not sure which part could be at fault. I have one of each on its way but really do not want to have to change the pump. I have also got VAG.COM although my lead is a bit tempremental but have not tried that yet.

 

Any ideas where I should go from here? :shrug:

[Topaz2008 0]

UPDATE :mad2: :-

 

Took the car out the weekend and the front brakes are dragging again. Still driving with the :censored: ABS unplugged.

 

Any ideas anyone?

[Topaz2008 0]

I have plugged the ABS unit back in now and connected with VAG.COM. There were some errors (see attachment) but as the ABS light is working ok then they must be old ones (the ABS unit was from another vehicle). I have cleared all the errors and none have come back in the 10 mile test run :D . I was also advised that the ABS cutting in when the vehicle was rolling to a stop could be caused by the rear sensor rings being damaged. I have changed these now and it has made no difference :( .

 

The issue with the front brakes dragging appears to be down to the calipers as I have jacked the car up and opened each wheels bleed nipple in turn. This did not free up the wheels so its not pressure doing it. I have ordered some new units and will fit when they arrive (the car did stand on the previous owners drive for a year) . So my outstanding questions are as follows

 

1. VAG.COM has a scope function. Is it possible on the Corrado to monitor the wheel sensor signals? This would enable me to jack up and spin each wheel and monitor the sensor readings to see if the sensor was working correctly

2. Do all the faults listed bring on the ABS light if they are current faults?

3. Can VAG.COM be used while driving the car for any diagnostic funtions?

[dirtytorque 0]

1.No

 

2. Any falt with the system will bring on the ABS light.

 

3.No.

[Topaz2008 0]

Update!!!

 

New front calipers have cured the binding brake issue so thats good news :D

 

As for the ABS I still have no errors on VAG.COM, which I expected as the ABS light was out, but the :censored: ABS is still trying to come in when the car is rolling to a halt with my foot on the brake. Short of fault finding with my wallet (new ABS sensors all round) I don't know what to do. It seams that VAG.COM does not have any diagnostic functions to test the sensors etc. I have checked all the sensors and rings and they look ok.

 

1. Is there any way of diagnosing which wheel the ABS is trying to release?

2. Is there a way of testing the senors?

[Richie_t 0]

Havent read all the thread so sorry if i have missed anything, you have done the right thing new calipers

 

As for testing abs sensors thats easy

 

unplug the sensor, jack up the wheel for that sensor, contet the senor to a multimeter set to read ohms and spin the wheel, no idea what the figures whould be but the resistant of the sensor should go up and down from one value to another.

 

The proper what to test them is to plug in an asilascope to actually see its wave form.

[StuartFZR400 0]

Glad the calipers now work - see, I said to look at the piston. The internal gubbins really do rust up sometimes; the brake fluid could have been airated.

 

ABS - hate this stuff. You've done the easy bit, replace the sensors. The only other bit is to ensure the ring is in perfect shape. Thereon its going to be an electrical issue with the ECU or something; pump etc. I'd be ***ered if I can remember the reading you should get off a multi-meter when spinning the wheel, but basically you've replaced the sensor, so you should get perfectly good readings; its further up the line IMO. Im surprised the VAGcom doesnt pick it up.

 

Try tapping on the shoulder of the long-timers on here like Andy/Jim/Tempest/Henny/etc - mods.

[Toad 0]

Or use the search....

[Topaz2008 0]

Tried the search but no luck, most of the posts refer to "I have error number XXXX what does this mean" Nothing from my old friend Google either. :shrug:

 

I did however remove the top from the ABS ECU plug so that I could access the wires and rigged a small 12v bulb up to the valve outputs. When the ABS cuts in the rear valve pulses so it looks like there is an issue with the rear sensors. Shame its a shared circuit so can't tell which side. As I have already changed the rear rings it looks like its sensors next. I am waiting for another ECU so I will try that when it arrives.

[Supercharged 2]

Rear sensors connect underneath back seats - worth checking continuity as I have seen a few bodged after the looms have been broken buy exhaust fitters or garages when changing axle bushes / suspension etc.

[Topaz2008 0]

UPDATE

 

And so the Saga continues....

 

I have now replaced both rear ABS sensors and when driven the ABS still kicks in as the car rolls to a stop :epicfail: :censored: . The test lamp I rigged up to find the offending ABS valve no longer detects the rear valve but is now detecting the front left side ABS sensor, so the next job is to replace that sensor. As I am doing that one I have decided to do the other side as well.

 

We will have to see how it goes. Watch this space for the next installment of ABS repair !!

[StuartFZR400 0]

A little lazy, im not looking above; did you not already replace the front sensors? I though you got an error on those from VAGcom?

 

Yeh, replace them, and be careful as said. Dont knock those little fella's heads, they're delicate. I found getting GSF cheapo ones were tricky to get into the location-hole; I had to squeeze them in tight - the gap to the rotor needs to be correct.

[Topaz2008 0]

A little lazy, im not looking above; did you not already replace the front sensors? I though you got an error on those from VAGcom?

 

No I did n't replace the fronts. In fact I had no errors (ABS light fine) with anything on VAG.com just the ABS cutting in as I rolled to a stop. The rears were replaced as I diagnosed which valve was firing with a small bulb. The rears fine now but one of the front valves is still firing.

 

Both front sensors arrived this morning, and I have been looking in my Bentley manual but there is no mention of a particular gap betwwen the face of the senor and the rotor. It looks as though the sensor bolts up tight in the hole and the gap is not adjustable. Does that make sense?

[Topaz2008 0]

So to conclude....

 

Its all fixed :D :D :D :D

 

The final problem was the left hand front sensor. When removed it looked fine (no damage) but must have been giving an intermittent signal. I road tested the car after replacing this sensor and the ABS works as it should. :clap: :clap: :cheers:

[Supercharged 2]

Nice one,always good to know what fixes these issues...

 

The ABS system can be quite fussy with the age and makes of the front sensors and they sometimes need to be matched to work properly.