Grease on Left Front ABS sensor - is the hub shot?

sehaare · December 13, 2010

Having some ABS issues, pulled the left front sensor and found grease on it - does this mean that the hub is shot?

Thanks
Steve

OneLever · December 13, 2010

Clean it off and put it back. Then pull it a little later and see if more grease is there. If the hub isn't acting up yet (making noises) then I wouldn't jump to conclusions.

Edit:
Please keep a question limited to one thread. From your other thread.

sehaare said:
ABS problems - which wheel?
How can you tell which wheel is causing the anti-lock brake system to act up (acts like a wheel is locking up).

I think that from inside the car I hear the noise coming from the front left, but that might just be because the break pedal and ABS master cylinder is on that side.

I went ahead and did a front brake job replace the rotors and calipers were fine, but I still have the issue.

Is there anyway to tell which brake the system thinks is locking up?

Thanks
Steve

There are code readers which can read the codes thrown by the ABS system. Regular low end readers usually can not. The 4WABS control unit (HCU and ECU) sits at the left rear top side of the engine bay. If ABS kicks in you will hear it coming from there. It sounds like a whining noise from the ABS pump, and quick clicking noises from the valves opening and closing quickly. You will also feel the brake pedal pulsate.

If there is a problem with the system the dash light comes on and the ABS system stops working. So if you have a dash light on and there is some sort of locking up issue then its not the ABS system.

CDW6212R · December 13, 2010

Steve, what model, and is the truck 2WD or not? 95-01 2WD trucks should have clean ABS sensors and no grease on them.

The AWD/4WD are sealed hubs with grease and the sensor goes into it. Those should be full of grease always with no air, and sealed always. Those sensors basically never fail unless damaged. Regards,

sehaare · December 13, 2010

OneLever said:
Edit:
Please keep a question limited to one thread. From your other thread.

Sorry about the multiple threads. I'm having some front end issues that I'm not sure are related. ABS and 4WD issues. I initially put everything into one thread and that was so long that I wasn't getting any replies (I probably wouldn't have replied myself

)

So I've tried to break up the different issues into a few more manageable threads. Here I'm trying to find out if the left front hub is shot which could cause all of my problems , in the other thread I'm trying to find out if I'm even looking at the correct wheel, and there is another thread trying to get info on the 4WD system.

Sorry not trying to use up all the bandwidth or ask the same question multiple times.

Thanks for your help
Steve

PS And I am getting some front end noise which might be coming from this hub, trying to narrow down where to start looking by trying to understand what my indications are telling me.

sehaare · December 13, 2010

CDW6212R said:
Steve, what model, and is the truck 2WD or not? 95-01 2WD trucks should have clean ABS sensors and no grease on them.

The AWD/4WD are sealed hubs with grease and the sensor goes into it. Those should be full of grease always with no air, and sealed always. Those sensors basically never fail unless damaged. Regards,

Sorry there is me being a dumbass, 98 Explorer XLT V6 SOHC with 4WD.

The whole story is that I had front end noise last year when the 4WD kicked in. This year I had to replace both lower Ball joints and a tire rod end. During that I removed the sensor to remove the steering knuckle. When I put it all back together the ABS started acting up like a wheel was locking up. Took a look at the sensor and it had grease on it. I now also have noise even if the 4WD is supposedly not on.

I had read another thread where someone was having ABS issues and said it was due to the hub getting grease on the sensor and was going to have to replace the hub.

Trying to pull the string a little more.

Thanks for any help that you can give me.

Steve

CDW6212R · December 13, 2010

I'd say what you read about a front ABS sensor going bad was not accurate. They aren't affected by grease, but debris does interfere with them. In the sealed hubs, there is no debris in them, just grease. The 2WD parts are open to the air, those attract debris, magnetically.

I would be hunting the noise by checking the hub bearings, CV joints, ball joints, sway bar end links etc.

OneLever · December 14, 2010

sehaare said:
I'm having some front end issues that I'm not sure are related. ABS and 4WD issues

I just read through the third thread and I think you are indeed tracking down two different issues. Since the 4WD noise is probably not related to your ABS problems I will leave that issue for your third thread. As a side note, less than one day for responses is not much. It can take a few days

sehaare said:
the ABS started acting up like a wheel was locking up

sehaare said:
The ABS started kicking in when I braked hard or when braking while going down hill.

Can you describe exactly the circumstances when you "braked hard"? I often have ABS kick in while descending steep hills which have snow and black ice. This is a correct function of the system because the wheels are indeed locking up as the brakes overpower the traction between the tire and ice. The system monitors the angular frequency of both front wheels and the rear differential tone ring. There is also an accelerometer to measure how hard the braking is. When the angular frequency falls below some threshold the magnitude of the acceleration is checked to see if this is a hard braking event. If so the HCU is activated and the ABS system you are familiar with kicks in.

Is your check engine light on or is the ABS light in the dash on constantly? When the ABS kicks in momentarily that light should also come on for a second or two.

As far as checking hub bearings there are obvious ways such as jacking up the vehicle and checking for noise as you turn the tire. Something I have not seen mentioned is that you could turn the tire by hand and hold a mechanics stethoscope against the spindle and various points on the driveline in that area. This would help detect and track the source of any noises if they can be detected while the vehicle is jacked up.

sehaare · December 14, 2010

The ABS acts up during the last few seconds of coming to a complete stop. If I do a rolling stop and slow down greatly but don't entirely stop I don't have an issue. I get the problem right before the car stops. It seems to happen more when I'm going slightly down hill (more weight on the front brakes) or when the wheels are straight (stopping before turning). It is an intermittent problem and slamming on the brakes doesn't cause it anymore than just a firm stop.

I've been driving explorers since 1994 (3 different ones counting my relative's car) and I've got a pretty good idea how the brakes are suppose to feel under a lot of different circumstances (even the hills of Seattle) and this isn't normal.

Hope that helps some.

Thanks
Steve

OneLever · December 14, 2010

At the risk of sounding like a broken record:

OneLever said:
is the ABS light in the dash on constantly?

The problem you are describing is apparently common. If you do a forum search using some combination of the keywords "abs" "stop" "low" [speed] several similar threads come up. The most common cause of the issue appears to be the speed sensor in the rear differential. It is a small $20 plastic part that is easily replaced.

However, since the ABS sensors are sealed units that begs the question, "What caused the sensor to fail?" As CDW6212R mentioned debris would do it. But debris in a sealed hub would either lead to bearing failure or indicate that it has already occurred. Debris in the rear differential would indicate at least that the fluid should be changed. The rear sensor apparently fails from corrosion on the exterior portion of it though so that may not apply.

I have taken the liberty of linking to specific posts within threads that are more pertinent to you. After reading the post go through the rest of the thread by clicking on the link in the top right corner of that page:

Link 1

Link 2

Link 3

In addition there is a TSB related to this issue: TSB 98-14-8. A link to a copy of it can be found in this post:

Link 4

After reading the TSB the question becomes; Does the vehicle pull to one side or the other when this low speed faulty ABS activation occurs?

budwich · December 14, 2010

as mentioned, grease is probably not your problem but debris is. I suspect that you might have been "banging" around during your ball joint work which might have caused a "weak bearing" to "displace particles" around inside the housing. As mentioned, you should be able to check the bearing "movement" to see if things are "OK". I drove with a significantly noisy hub for over 10kkm before is "failed" with by rubbing on the brake caliper.

sehaare · December 14, 2010

Thanks for taking the time to link to all of those post. I'll go through them after I get off of work today (and maybe before if the boss isn't watching).

I'm 99% sure that the ABS light is not constantly on and I'm not sure if it comes on when I'm having the issues. I'll try and recreate the problem and check but that will have to wait until after work since the boss frowns on driving thru the office

Thanks again and I'll let you know what I find
Steve

budwich · December 14, 2010

onelever... I don't believe the abs slight should come on ever during "normal" operation (outside of "check bulb,etc")... not even for a "short bit". Its a system warning light that there is a problem not an indication light that your abs has "fired". IF it comes on, even momentarily, you have an issue with the system.... probably not major but an issue.

CDW6212R · December 14, 2010

Steve, the rear ABS sensor(also the VSS sensor) is often the answer to intermittent ABS pulsing at low low speeds. I would check out the front end parts well because you are hunting a noise.

Once you are fairly sure that the hubs are okay, then I'd take the chance and buy a new rear ABS/VSS sensor. That would be the first part I'd guess at and change, because many others have and it solved their problem. I haven't experienced that problem except maybe twice ever, so I'm suggesting this based on reading of it here several times. Regards,

OneLever · December 14, 2010

budwich said:
onelever... I don't believe the abs slight should come on ever during "normal" operation

You are right I was thinking of something else.

The ABS light should only come on for about 3 seconds during the ECU self test when the ignition is placed in RUN after being in the OFF position. The HCU and ABS pump are then tested when the engine is started, or if the brake pedal was being held down on engine start it is done at 4 mph. That dash light is called the 4WABS Failure warning lamp in the wiring manual.

sehaare · December 15, 2010

After reading the links, Looks like I need to do some more test driving to see if It pulls to one side.

I doubt that it is the rear sensor since I didn't have this issue until I had worked on the front end replacing the lower ball joints which did require quite a bit of pounding to break the upper ball joint free. And I'm a firm believer that the problem is usually with the last item that you worked on.

I am getting front end noise when driving without breaking. If the hub were going bad it could explain both the ABS problem and the noise. So if the car starts pulling to the passenger side when I get this issue it would be time to replace the drive side hub.

Steve

budwich · December 15, 2010

I guess the question is what do you mean by "when I get this issue"? are you referring to pulling to one side during breaking?, noise coming from the front, pulling going down the highway? Basically, all / some of those could be cause by a bad caliper. When you did your front end work, and removing the calipers, did the pistons go back in "easily" or did it take lots of force to get them to "release". My guess is that you have a "seizing" caliper and its on the side opposite the pull IF the pulling occurs during braking. IF the pulling is during driving, then its likely the side that is pulling.

sehaare · December 15, 2010

budwich said:
I guess the question is what do you mean by "when I get this issue"? are you referring to pulling to one side during breaking?, noise coming from the front, pulling going down the highway? Basically, all / some of those could be cause by a bad caliper. When you did your front end work, and removing the calipers, did the pistons go back in "easily" or did it take lots of force to get them to "release". My guess is that you have a "seizing" caliper and its on the side opposite the pull IF the pulling occurs during braking. IF the pulling is during driving, then its likely the side that is pulling.

I had thought about a bad caliper and hadn't ruled that out completely yet.

The "issue" is the ABS acting like a brake is locking up just before coming to a full stop. It happens less that 5% of the time. I haven't felt any pulling during breaking but wasn't really looking for it. So I need to go for a drive to see if I can get the ABS to act up and see if one side pulls which according to the TSB indicates that the other side is the issue (The ABS is letting up on the side opposite the pull).

There is no pulling when going down the highway (but I'll check again to be sure)

The calipers compressed normally when I used a C-clamp to make room for the new pads. If it was a seizing caliper I would think that I would get it more than 5% of the time and it wouldn't wait until I'm almost completely stopped before seizing. But I could be wrong, and bringing it up here makes me think it over again.

The windchill here has been below zero and they've got me working nights this week so I haven't gotten much done on this other than read replies here. I've got to drop off another car for an alignment and then I should be able to take this out finally this afternoon to check on this.

Thanks for you help
Steve

sehaare · December 15, 2010

Took the truck out and put it through its paces. It does not pull when going down the highway. The only way that I can get the ABS problem is when I come to a full stop while turning to the wheel to the right. Never happens when turning left and only a time or two with the wheel straight. It awful hard trying to determine if the truck is pulling when it happens with the wheel turned but I think that it is pulling somewhat to the right (but that is the same way the wheel is turned so I'm not 100% sure).

What would cause this to act up when turning right?

Thanks
Steve

OneLever · December 15, 2010

When turning right you are putting a lateral force against the left wheel bearing inside the left hub assembly. This is coincidentally the same hub your first post mentioned. I would remove the left wheel and rotate the axleshaft while listening for noises. Try the same on the right side.

Unless you hear anything on the right to contradict this hypothesis. Go ahead and remove the left hub assembly and test the bearing motion for binding and noise by hand. At that point you should be able to tell.

OneLever · December 16, 2010

In case you didn't see it. Here is another thread which is related to yours which the original poster just updated.

Grease on Left Front ABS sensor - is the hub shot?

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