VicG

2001 1.8T

ABS kicks in upon normal braking (< 5mph) regularly. Searched on AW and found out that the wheel speed sensors can get dirty and cause this problem. I pulled the fronts and cleaned them both. Did not help the problem.

Today I tried to do the rears, but broke off the mounting bolt on the 1st one so I did not attempt to pull the sensor (I'm not ready to drill out the broken bolt & retap this just yet) so I just left it.

Figured I'd fire up Vag-com (ISO-COM/311-2) so see if there was a problem with the ABS controller, and try to use measuring blocks to see if there was weak/dead sensor.

I can log into the ABS module, shows no fault codes. If I click on Measuring Blocks, block 001 shows "Speed" "Speed" "Speed" "Speed". I assumed these were the 4 wheel sensors. So I start driving and see the KM/HR go up on each. After 1 min, I get "can't communicate with controller, Retry?" and measuring stops. If I click to retry, it fails repeatedly.

I can't seem to hold connection to the ABS module. I think it also did this with the key in the "on" position before I did the test drive.

Is there some type of problem with Vag-com hold comms with the ABS module?

Bracketracer

Once you get over a certain speed (about 5-10 mph, I think), communications will stop, so people don't do something silly like run pump cycling routines and such while driving.

2001 1.8T what?

I've run across a rash of rear axle stub reluctor wheels cracking and causing the abs to cycle at low speeds when braking.

VicG

a couple months ago.

How do I diagnose the rear axle stub reluctors?

Is this something the home mechanic can repair?

(I did not fix the wheel bearing because I don't have a press, otherwise I would have attemtped it).

I tried to look for anything that might have the appearance of a "gear tooth" but cant see much.

Bracketracer

Now there might be an issue. Sometimes...not often, but sometimes, when a rear bearing is replaced, there are two items that could get damaged during the replacement, depending on what equipment they used to replace the bearings, and how they exactly did them.

A little detail: A rear wheel bearing can be done, start to finish in 30 minutes using the right tools and knowing the right (proper) shortcuts. If the dealer has a Hubshark, and does not completely remove the rear axle, then I seriously doubt that they could have damaged anything during bearing replacement. If they go the hydraulic press route, then there is definitely a possibility of a part being damaged, since the rear hub carrier has to be completely removed, including the ABS sensor.

Anyway, yes, you can check the reluctor rings yourself, and here's how:
Hopefully, you have removable wheel center caps, and I'm assuming this for the first step. Remove center caps, and have the car in park. You'll need a 1/2" drive 14mm Allen socket with a short extension. Loosen the axle bolt a turn or so. Now jack the car up and remove your rear wheels. You will need an 18mm socket and ratchet, and 19mm wrench to take the upper control arm bolt out. Once you've gotten the control arm apart from the spindle, undo the axle nut completely. Pull the top of the spindle toward you, and you should be able to separate the axle from the hub and inspect the reluctor ring on the axle stub. Look closely for cracks. Shouldn't be hard to see if there's a problem.

VicG

replacement. It is solidly frozen in place, I cannot budge it at all. I'm using channel locks to twist the brass part of the sensor (I was going to clean them like the fronts...)

Does that kinda mean they used a hubshark, since the rear sensor was not disturbed?
I can call the dealer to confirm. I only mentioned the press because when I was researching the procedure to change a bearing I was told that's what was needed. I've changed bearings on older cars, using a drift to tap out the ring and a socket to tap in the new one (timken type bearings).

I have everything but the 14mm axle allen socket, I'll get one. Sounds like a simple enough job to do.
Thanks,
Vic

VicG

no errors, and as I said it did read the speed equal on all 4 wheels...

Bracketracer

and for some reason, most of the rear axle problems I've seen have been on B5 1.8 Avants, not 4-doors.

Often times, the glitch or spike happens way too fast for the scan tool to catch, at least in my experience. None of the cars I've done with broken rings have thrown any codes.

Bracketracer

can be an ABSOLUTE bitch to remove depending on the car's mileage, climate, etc. Most of them I've had to drill, torch, hammer, and pray out of the hole. If you've tried to twist it out, I can about guarantee the the sensor is f'd.

Now concerning the bearing replacement, most cars, yours included have the large sealed type of bearings, which look like a cylinder. No more tapered-type bearings with removable races and such. Takes a LOT of pressure to press the bearing assemblies in and out, hence the need for a hubshark (which the dealer probably has) or a 10-20 ton press.

However, like I mentioned earlier, inspecting the axle stub and abs ring is pretty easy.

VicG

sucessful.

It's weird that an Avant style vehicle would have more trouble issues than a 4dr, as I would assume the suspension components from the lower body down would essentially be the same.

Oh well. CE engine light on for the wife on way home from work tonite, read code with VAG-COM it says something about high coolent temperature - but open hood and find the "L" hose broken. Patched in a temp fix with some tubing till I can get to dealer for new part.

Arghhhh. EVERYTHING breaks after the warrenty expires.

VicG

do you know the part numbers for left/right axle stub for an 01? (in case I need to get them)