replace hub assembly?

[FHfirefighter]

Ok, so my problem started with a grinding, groaning noise from my front driver's side brake, typically at low speeds just applying the brakes to come to a complete stop. I inspected the pads and rotors (both sides to be sure) and they were all in great shape. But I did notice that it looked like someone had set off a grease bomb in my (driver's side front) wheel weel; there was grease all over the hubs, breaks, suspension, etc, and slung onto the wheel well body itself. My theory is something (bearings?) failed in the hub assembly area around where the boot protecting the axel meets the hub assembly. This is/may be causing the hub move around more than usual, causing the brake shoes to press against the part of the rotor that they don't usually contact (which is rusty, thereby causing the noise). I think it only happening at low speeds works with this theory because the wheel spins like a top: when it's faster, it's going to have a tight, steady spin...but when it slows down, if there is room for it to wobble, it will wobble more as it spins more slowly.
So basically what I'm asking is does this sound like a good theory or am I off-base? I'm planning to order a new hub assembly: (http://www.1aauto.com/1A/hub_assemb...5&ovchn=OTHER&ovcpn=Froogle&ovcrn=&ovtac=CMP), but I wanted to get some opinions before I drop close to $200 and find out it's not the problem. Thanks!

 

[dogfriend]

Did you inspect the CV joint boot? I think your theory of a failed hub is plausible, but if you have that much grease slung about in the wheelwell, I'm guessing that the CV boot may be torn instead. Just a hunch.

 

[DeRocha]

A ton of grease in the wheel well is not a good sign.. I'm not sure if the bearing hub assembly contains enough grease to make that mess, or be at the right angle to fling it onto the wheel well. It sounds like the cv joint boot has torn as Dogfriend as mentioned. When the rubber boot tears it obvioulsy will throw out the grease and begin to wear.. A common sign of CV wear is that you'll begin to hear a grinding noise when making sharp turns, but no noise when going straight.. Eventually the grinding will get worse and begin to occur with any turns...

 

[FHfirefighter]

Thanks for the replies, guys. The grease is still a bit of a mystery, but it MAY be from when I changed the ball join there; I put a bunch of grease in between the hub assembly and the boot where the axel comes into the hub (nothing to do with the ball joint, I know, I just greased everything I saw while I had stuff apart). I've come to the conclusion that I really shouldn't have put the grease in there because there is no seal between that part of the boot and the hub assembly to hold grease in. The mystery part, though, is that I put all that grease in there months ago, but I didn't start comming out until about the same time I started hearing the brake noise.

Unfortunately, this new info came with a $170 price tag for a new hub assembly, and info is about the only thing I gained from it: After replacing the hub assembly, the grinding I described in the first post hasn't changed a bit . The bearings did appear to be a little worn, though, because the old hub assey was a lot looser and slooopier than the replacement...still, it did nothing for my brake problem.

My new theory is maybe one of the cylinders in the brakes is bad. Maybe one side is pushing more than the other, causing the pad to skew a little, enough to contact the rusty part of the rotor just a little. There pads are not worn unevenly like they would be if this was the case, but since this just started and I've only driven it maybe 15 miles since it started, maybe it hasn't had enough time to wear the pads unevenly. After careful inspection of the rotors, though, I'm even more sure that it's a slightly misplaced pad contacting the rusty part that's causing the sound because you can see the partially clean metal on the innermost edge of the outer rust ring where the pads have recently started contacting and wearing away the rust.

So...anyone got an opinion? Does this new theory sound plausible?

 

[dogfriend]

Not sure about what is going on but if you notice a different wear pattern on the rotor you should investigate whether the pad is broken, or you have some debris that is rubbing, etc. This is serious, you should correct it ASAP.

Another possibility is that you have a stuck or sticking caliper; the caliper should slide or "float" on the caliper pins to equalize the pressure on both sides of the rotor when you apply the brakes. If the caliper is stuck, it will continue to rub on one side even when the brakes are released. Again, you should fix ASAP.

 

[FHfirefighter]

Another possibility is that you have a stuck or sticking caliper; the caliper should slide or "float" on the caliper pins to equalize the pressure on both sides of the rotor when you apply the brakes. If the caliper is stuck, it will continue to rub on one side even when the brakes are released. Again, you should fix ASAP.

I think what you're saying is sort of along the same lines as what I said about the pads hitting the rotor unevenly due to different pressures from the cylinders, right? Any suggestion on how to check if this is the case, other than just waiting to see if the pad(s) starts wearing unevenly?

 

[FHfirefighter]

Ok, well I'm going to work on it today. I was planning to replace the caliper, thinkning it may be one of the cylinders gone bad, but what dogfriend says about the caliper pins makes me wonder, too. not really sure which direction to go right now...

 

[dogfriend]

Sorry, I didn't see your previous post; I would have replied sooner.

When you replace the caliper, you will have solved half the problem; the bore that the caliper pin goes into will be nice and clean. You should clean and inspect the caliper pin; if it is corroded or otherwise damaged you should replace it. For the pressure to be equal on both brake pads, the caliper must be able to slide freely on the caliper pins.

Also, make sure to lube the caliper pins with a thin coating of caliper pin grease. This is not regular grease, but is a high temp silicone grease. They have it at the dealer or you can get it at a good parts store like Napa.

 

[FHfirefighter]

Well it's all over, with valuable lessons learned. Most importantly, start with the simpilest solution first, even it doesn't make sense: turns out I was suspecting the wrong side all along. I sanded away all the rust that I thought the driver's side pads were contacting, but my grinding noise was unchanged. Finally, I just said F it, I'll just replace the pads and rotor in case the spot the pads are hitting is still too rough. So of course I have to replace both sides, even though I'm sure the passenger's side is ok, right? So I get to passengers side and what do I find? THERE'S NO PAD. The back part of the thing is there, just not the part that actually is supposed to contact the rotor. What was contacting the rotor was the rivets that used to hold the pad in. A (mechanic) friend said it looked like the pad had cracked and fallen out as opposed to wearing down to that point because the grinding started suddenly with no squeeking or increase in intensity over time.

So the moral is never completly trust where it sounds like it's comming from. I had 3 different people listen to it, sitting in the passengers seat as well as driver's, and standing outside on both sides as well. Everyone was sure it was the driver's side, but it was passenger's all along.

Well thanks to everyone who gave their advice. I'm a little embarrased but hopefully some people can learn from my mistake.

 

[dogfriend]

The best way to learn is by observing other's mistakes.

Glad you solved the problem.

 

[FHfirefighter]

Crap, I just re-read your post, dogfriend. I not only lubed the caliper pins with regular grease, I even wipped all the old stuff off (though since it was about the consistency of dirty chewing gum it was probably doing more harm than good anyway). Should I worry about this?