What did I do, and how do I fix it?

[Ironwagon]

This post is in follow up to a post I had a while back regarding brake chatter after a 100 series pad swap on my 80. As I mentioned then, I had gone through the front end of the cruiser rebuilding the knuckles and swapping brake pads, I replaced the rotors as recommended, seals, etc.. The problem was described then as chatter when brakes are applied, but a more accurate and up-to-date description follows:

Here’s the problem as best I can figure. For some reason the ABS activates under normal braking conditions (when brakes are applied around 30 – 40%) typically when approaching a stop sign which causes the cruiser to pull left (drivers side). This only happens when the ABS light is OFF. However, on occasion the ABS light will come ON and while it’s on the brakes works fine, no pulsing under any conditions. Another oddity is that under very hard braking there’s no pulsing and no pulling regardless if the ABS light is on or off.

I just took the cruiser into a local shop and they ran a diagnostic on the ABS sensors. What they discovered was an intermittent, abnormal waveform on both the left and right sensors. They checked the deceleration valve and said it checked out ok. They put it back on the street for a road test and it drove fine for about 20 minutes then started acting up again. They then hooked up the scope during the test drive and the same intermittent, abnormal wave form appeared.

Their conclusion was that as unlikely as it seems, both sensors had failed at the same time (which would have been post brake swap). Their suggestion was to purchase new sensors (@ nearly $400) and that MAY fix the problem. They said may because they are as baffled by these symptoms as I am.

I’m hoping some of the more experienced folks on this board can enlighten me.

Thanks in advance for the input.
Justin

 

[ryanjl]

Were you careful in removing the sensors before you pulled the birfields and axles (assuming you pulled these when you did your rebuild)?

If you didn't, they most likely were damaged then.

If that's the case, PM cruiserdan on this board to get a better price on your sensors.

 

[Rookie2]

I assume the easy thing has been done... pull and wipe down the sensors, check for any abnormal scuffs, damage etc..

 

[Ironwagon]

I did remove the ABS sensors prior to pulling the birfs and was careful when doing so. The sensors were removed and cleaned a short time after the brake job, and they didn't look any different than they did when the break job was done. I will take another look though.

One comment the shop had when they were doing their diagnosis was the presence of grease on the ABS gear, how much I'm not sure. Could that be the issue?

 

[Rookie2]

One comment the shop had when they were doing their diagnosis was the presence of grease on the ABS gear, how much I'm not sure. Could that be the issue?

ABS Gear??

Please tell me your not referring to the ABS ring.

 

[Ironwagon]

ABS Ring is correct.

 

[ogsuv]

I removed my abs sensors and reinstalled carefully too, but experienced the same problem.

I had to take them both out , scrape the mounting surfaces spotless, reinstall sensors, and was fixed. Just a thought..........

 

[cruiserdan]

It would be impossible to have a grease-free exciter ring unless you forgot to pack the knuckle.....

Since the sensors are magnetic, it is possible that they may have picked up some stray metal bits. I would pull them and get a look at the end.


D-