HELP - rear abs sensor broke in half!

[Carnage_uk]

Hi guys,

I'm really in need of some help, my 2004 A4 has had the abs and traction light on for the last few months, vagcom said it was rear right speed sensor. I bought a new sensor and went about replacing the old one... Nice easy job I though

The Allen bolt for the sensor was pretty badly rusted so I used heat and penetrating oil, as I was trying to loosen it SNAP the head sheared off! I thought I'll worry about that after let's get the sensor out first, it wouldn't budge so I used a chisel round the edge to free it off and SNAP the top of the sensor sheared off.

So now I'm left with a sheared bolt and half a sensor stuck in the hub. Can someone please advise me the best way off getting sensor out, I've tried drilling it from behind but there's hardly any room and I'm not making any progress, would it be better to take the brake disk off and try and attack it from the front? Also I can get the the sensor from the side (as it goes from the bracket into the dust shield, I am unsure if this is actually the sensor or a collar that the sensor goes into?

Hopefully that makes some sense, I'd be eternally grateful if someone can advise me of how to fix it =)

[zollaf]

remove whatever you need to so as you can get a punch in behind it and hammer it out. as for the snapped bolt, you can weld a nut onto the remaining stub and then turn that out. the heat from welding it will free it off.

[Carnage_uk]

remove whatever you need to so as you can get a punch in behind it and hammer it out. as for the snapped bolt, you can weld a nut onto the remaining stub and then turn that out. the heat from welding it will free it off.

thank you so much for the quick reply, just to confirm you mean hammer it from the brake disk side of the hub as to push it back out the hole it goes into?

[zollaf]

yes, remove it the way it should come out. they either pop out really easy with a twist or take ages and cause loads of grief.

[Carnage_uk]

yes, remove it the way it should come out. they either pop out really easy with a twist or take ages and cause loads of grief.

Thankyou!!

[ianlovatt]

For what it's worth here's my experiences of the same problem (sheared bolt and snapped sensor):
Rear wheel speed sensor issues

cheers
ian

[Carnage_uk]

For what it's worth here's my experiences of the same problem (sheared bolt and snapped sensor):
Rear wheel speed sensor issues

cheers
ian

Thanks Ian I'm sure the shoe lace trick will come in handy, just a few quick questions...

It sounds like you did all the work from inside the arch, am I right in thinking you didn't have to remove the brake disk?

Did you hack saw the middle of the sensor which is visible as it goes from the mount into the dust shield? I wasn't sure if that was the sensor itself of a sleeve as the surface felt metallic whereas the new sensor is plastic.

Do you think it's possible to fit the sensor securely without the bolt? I need to get it fitted for its upcoming mot and would drill/tap it when I have the time and tools, also did you drill it in situ as the space seems tight?

Thanks again

[ianlovatt]

I did all the work from inside the wheel arch and didn't remove the brakes.

There wasn't any 'sleeve' on mine - just a round hole in the mount for the sensor barrel to go through towards the brake dust shield. Hard to tell exactly what you mean regarding sawing - I cut the barrel of the sensor that was sticking in towards the brakes through the shield up into up into "slices" sawing close to the dust shield then when a chunk was cut, carefully dragging the remaining bit of sensor back out from the dust shield before cutting again. I used a punch to clear the bit of sensor that filled the mount. Shame the pictures I took are so poor but my phone's not much newer than the car!

I drove around with a couple of zip ties holding my sensor in for a day

I drilled in situ using the crappy flexible drill shaft in the link


Thought I was the only one to leave jobs to the last minute before MOT...

Good luck
ian

[Eibbor]

I've just fitted my new rear sensor last night. I too had a snapped bolt. I found removing brake disc gives you space to hit the sensor through (in pieces I may add) with a punch.

Rather than using a flexible drill shaft which to me screams injury waiting to happen lol, I removed the hub assembly (21mm allen socket - tight as ****)
This along with the disc guard removed gave me all the room I needed to drill the bolt out.

When I come to do the other side I will remember the shoelace trick. Audi do not make it easy to work on their cars I'm slowly finding out!


Sent from my iPhone using Tapatalk

[AvantGeorge]

Just swapped the NSR ABS sensor on my B6 A4 and thought I’d share my method:

1. Remove wheel
2. Remove calliper (2x13mm)
3. Remove calliper carrier top bolt only (8mm Allen key)
4. Tap calliper carrier round (pivoting on lower bolt) to allow removal of disc.
5. Remove 3 Torx holding dust shield.

Access to ABS sensor is now much easier.

6. Attempt to remove 5mm Allen Bolt holding ABS sensor, will likely shear off.
7. ABS sensor will probably be ceased in too so with good access to the front and back, use whatever means necessary to remove the sensor. (Hammer and chisel was my choice), sensor ended up in several pieces.
8. Remove ceased bolt stump. I did this using a small air drill from the back. Wiggle the drill handle somewhere in behind the shock and anti-roll bar. Aim to get a small drill through the middle of the bolt and work through the sizes. I was slightly off centre so ended up drilling a slightly oversized hole, makes no difference.
9. Clean up the sensor hole, slot new sensor back in and nut&bolt right through To hold in place. I used an m8 with nyloc. If you’re accurate with drilling you may be able to re-tap but it works perfectly fine to drill a clearance hole and nut&bolt.
10. Sensor plug is located behind the panel next to the rear seats. I removed the rear seat base and an 8mm bolt which holds the side bolster in. This provides good access to the plug and makes re-routing easier.
11.Reroute new sensor. I found that attaching string to the sensor plug when removing the old one made it much easier to pull the new one through the bodywork. A challenge without a ramp, but certainly do-able on a jack.
12.Wind brake piston back in, refit in reverse and lights should all be out!