ABS Sensor Replacement

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JHZR2

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I'm a bit annoyed, but my BMW ABS sensor seems to be busted.

Speedometer had a glitch, then got an ABS light. Went away when I turned the car off and restarted. Showed up about 190 miles later. Codes indicate left rear.

Got an OEM part, ready to do it. $40 or so.

An online DIY shows it's just held in with a single screw. Not much to it. But it's stated to coat with a long life grease.

That means that whatever I remove also had a long life grease.

Ive never replaced a sensor before. I'm not that concerned, but I seem to recall that the abs sensor magnets on a hub should never be touched, and that contact with them or getting dirt on them can cause them to not work. That may not be true or lost in translation/my memory.

So what should I use to clean the spot wher the sensor is mounted? Paper, popsicle stick, screwdriver, etc? Are chemicals Ok? Can you go too deep and damage the hub, magnets, bearings, etc?

Once clean, I'll coat the sensor lightly and install. How much is too much? Coat the whole thing or just the sensor shaft or top (I.e. Use the grease more as anti seize or anti-rust at the top?).

Is dielectric grease ok for the other end?

DIY that's very similar:

https://www.pelicanparts.com/BMW/techart...Replacement.htm

Thanks!
 
Usually you get info about a distance between a sensor and the hub via google/autodata/....

Use ceramic grease/paste to lubricate...or regular lithium grease you have in your garage...avoid any grease with metal parts in it (copper grease or antisieze with zinc etc) because it can interfere with sensor readings... Brakecleaner/wd40 /... For cleaning
 
Are you supposed to coat the screw with long life grease or the sensor or both?

In my 98 sienna the screw head snapped flush. Had to be drilled out. For the screw I used anti seize. Sensor was left dry.


I would make sure you use plenty of penetrating fluid before trying to remove it and use a wire brush as well to knock the corrosion off.
 
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If the car has seen winter and salt it can be a nightmare but hopefully not. Soak it down good with penetrant a couple of days before as cheap insurance.
Once the bolt is out try and wiggle it before prying on it, if it moves go ahead and pull it, if it wont move try moving it left to right with pliers and pry it up at the same time, if it breaks you have a bit of a job ahead of you. If this happens post or PM me.

On these I use marine never seize or Green Grease, the stuff is so thick and tacky and waterproof, wear nitrile gloves its a bugger to get off but it works great.

Don't worry about metal anti seize you can also use it just don't get any on the magnet tip. The sensor body is insulated and in a metal housing anyway so it doesn't make any difference.

https://www.amazon.com/Marine-Grade-Anti...&dpSrc=srch

https://shop.advanceautoparts.com/p/gree...mp;gclsrc=aw.ds
 
Originally Posted By: Kamele0N
Usually you get info about a distance between a sensor and the hub via google/autodata/....

Use ceramic grease/paste to lubricate...or regular lithium grease you have in your garage...avoid any grease with metal parts in it (copper grease or antisieze with zinc etc) because it can interfere with sensor readings... Brakecleaner/wd40 /... For cleaning


I think depth is set by the sensor body flange:

pic08.jpg


For cleaning, it's safe to assume that whatever flows through won't harm the magnets and whatnot on the other end of the hole? Id think it all has to be pretty well sealed given exposure to road water, but Ive not looked in detail yet.
 
Originally Posted By: Trav
If the car has seen winter and salt it can be a nightmare but hopefully not. Soak it down good with penetrant a couple of days before as cheap insurance.
Once the bolt is out try and wiggle it before prying on it, if it moves go ahead and pull it, if it wont move try moving it left to right with pliers and pry it up at the same time, if it breaks you have a bit of a job ahead of you. If this happens post or PM me.

On these I use marine never seize or Green Grease, the stuff is so thick and tacky and waterproof, wear nitrile gloves its a bugger to get off but it works great.

Don't worry about metal anti seize you can also use it just don't get any on the magnet tip. The sensor body is insulated and in a metal housing anyway so it doesn't make any difference.

https://www.amazon.com/Marine-Grade-Anti...&dpSrc=srch

https://shop.advanceautoparts.com/p/gree...mp;gclsrc=aw.ds




Fortunately the car is not a winter driver, and I have both moly AS and tacky waterproof grease. Planning to use Schaeffers 238 on the body and a bit of marine AS on the bolt.

Thanks!
 
Might want to check the module, but I believe the magnet is inside the module you are swapping (touch the sensor against something ferrous, like the fridge). The ABS tone ring is ferrous and is used to direct the magnetic field through the sensor--the sensor is backbiased. I have a tough time believing that grease on the sensor will do anything--it would have to be ferrous to have an impact.

I'd be more worried about the sensor sitting out from the hub (due to rust buildup) and placing too much distance between sensor and target.
 
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It should be no problem being a summer car. There is no adjustment on these where it sits on the flange is the correct distance.
 
Originally Posted By: supton
Might want to check the module, but I believe the magnet is inside the module you are swapping (touch the sensor against something ferrous, like the fridge). The ABS tone ring is ferrous and is used to direct the magnetic field through the sensor--the sensor is backbiased. I have a tough time believing that grease on the sensor will do anything--it would have to be ferrous to have an impact.

I'd be more worried about the sensor sitting out from the hub (due to rust buildup) and placing too much distance between sensor and target.


I saw a YouTube video of that exact issue .
 
Originally Posted By: WyrTwister
Originally Posted By: supton
Might want to check the module, but I believe the magnet is inside the module you are swapping (touch the sensor against something ferrous, like the fridge). The ABS tone ring is ferrous and is used to direct the magnetic field through the sensor--the sensor is backbiased. I have a tough time believing that grease on the sensor will do anything--it would have to be ferrous to have an impact.

I'd be more worried about the sensor sitting out from the hub (due to rust buildup) and placing too much distance between sensor and target.


I saw a YouTube video of that exact issue .


Want to say it was GM & some calipers on their trucks with that issue?
 
Originally Posted By: JHZR2
How much should I try to clean the hole??




Thanks!!


Just clean it up a lightly with 400 then blow it out with some brake cleaner.
 
Originally Posted By: supton
Might want to check the module, but I believe the magnet is inside the module you are swapping (touch the sensor against something ferrous, like the fridge). The ABS tone ring is ferrous and is used to direct the magnetic field through the sensor--the sensor is backbiased. I have a tough time believing that grease on the sensor will do anything--it would have to be ferrous to have an impact.

I'd be more worried about the sensor sitting out from the hub (due to rust buildup) and placing too much distance between sensor and target.


Fortunately as soon as I did about 3 mph, all lights went out. All seems well now.

I was fearful that a car that sits a lot outdoors could have had water seepage affect the bearing and shift the position of the rings on the hub. I had read of that happening.

Fortunately an easy success.
 
In the video I refereed to , I think " rust jacking " was the problem . The video also stated , in the rust / salt belt , it was common to destroy the sensor while getting it out .
 
Originally Posted By: Trav
Nice when the job goes easy. The ones I do are mostly are ones that are rotted tight in there and the bolt breaks 1/3 of the time.


Which is why this is infuriating - 21k miles on a 2011 car.

And low mileage is why I'm relieved it wasn't rust jacking...
 
That not much. I wonder if the magnet picked up any metal, that will cause it to malfunction. I would spray a little fluid film on it yearly where the bolt is and flange.
 
Originally Posted By: KrisZ
For a car that for all intents and purposes is pampered, I'm surprised how much gunk was on it. I can only imagine the ones that are driven during winter.
crazy2.gif



What is that gunk? Grease that has picked up dirt and rust?

Originally Posted By: Warstud
To late now...but I would of tried cleaning it first


IMO the real question is what is the best way to test it?

The time spent is really in jacking the car up and getting the wheel off, not swapping the sensor. I can't imaging a shop would clean and replace, for a $34 OEM part. But if it could have been due to gunk, and there was a way to test it as good, I'd consider keeping it as a spare. Otherwise I'll chuck it.
 
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