Strange noises

[Tleg93]

I am in need of help I think. I have a sound coming from my front driver side wheel area. I've had two garages look at it and they both said they couldn't find anything but acknowledged that there was a loud noise. The noise sounds like two metal surfaces smacking together. I've replaced the front struts and put new brake pads along with all of the hardware that goes with it. A buddy and I were replacing the pads when I saw that my tie rod was all screwed up. It looks like it twisted somehow. The boot was all twisted up and the tie rod looks turned when the wheels are straight. Any ideas, I'm at the end of my rope here and I'm wondering why all these mechanics didn't see the tie rod damage. I would appreciate any help here.

[Tleg93]

I feel like kicking myself right now. I just took my car to the garage to find out what the noise was and they discovered something I should have discovered. The caliper mounting bolts were hanging out of the holes. The horrible thing is that this has been looked at a couple times by different people, including me, and they never saw it. I guess when we torqued the bolts down we got a false reading due to the rusted threads.
A word to the wise: Never blindly follow torque specs. Use some common sense and make sure that the mouning bolts are nice and snug and free of corrosion.

I hope I've reproduced the post accurately.

[vrg3]

Well, I personally didn't reply to your post because I had no idea what your car's problem might be.

It's a good point you bring up, but I have to disagree strongly with the notion that mounting bolts just "need to be tight." There's an important reason behind torque specifications. When torqued properly, a bolt deforms elastically a little bit. That causes a certain desired amount of clamping force. If overtorqued, it can deform inelastically, resulting in damaged threads and many other potential problems. If undertorqued, it doesn't deform at all that way, and the clamping force is greatly reduced.

But, the trick here is this: the amount of stretching the bolt undergoes depends on how far you tighten it, and torque is an easy way to measure that, but the torque required to tighten the bolt depends heavily on the amount of friction between the internal and external threads. You're exactly right when you say you got in trouble due to the rusty threads. The specifications are (in general) written for clean dry threads.

For example, if you put anti-seize compound on a threaded fastener, you need to reduce the torque specification by about 25 to 35 percent. Conversely, if you somehow increase the friction in the threads, you need to increase the torque specification to achieve the same amount of elastic deformation and the same amount of clamping.

BUT, if you can at all avoid it, you shouldn't put a rusty bolt back in your car! Oxidation reduces the ability of the bolt to stretch elastically and it clogs the threads which can damage the mating set of threads and throw off your torque reading. It's a bad situation all around.

At the very least, always thoroughly clean off all threads on any fastener before installing it. At a minimum I use a wire brush and either brake cleaner or isopropanol or ethanol. If you're lucky enough to have a tap and die that fit the threads, it's a good idea to go over them to restore the threads more and clean them better. A poor man's tap and die can be made out of stainless steel bolts and nuts; just use a grinder or even a Dremel to cut flutes in. Never ever ever thread on a fastener when you know the threads aren't clean.

Sorry, I don't mean to rant, but threads simply don't get the respect they deserve from people working on cars, especially novices.

Thanks for posting what the problem was, Padishar. I really strongly suggest that you replace those bolts with new clean ones and give the threaded holes at least a good blast of brake cleaner. If it's the bolt I'm thinking of, the list price from Subaru is like 75 cents.

(commentary by jason: without reading Padishars initial rant, i've got to say that this is probably the perfect example of an information packed post coated with expirence and dipped in influence. I'd like to take this time to thank Vrg3 for this. It's REALLY good advice.)

[Tleg93]

You're right, I've just been so worried about the problem that I was getting upset about it. I'm really just getting started at all of this. I'm no mechanic just a curious person who wants his automobile to look and run as good as possible. My bad.

[vrg3]

Hey man, I want to apologize if I came off as condescending or anything like that. I didn't mean to offend. I just want to share knowledge. Most of us aren't experts; we're all just people who want our cars to look good and run well.

Out of curiosity, why did you erase all the stuff in your post? It would benefit future readers more to see all of it..

And let me say that I can definitely sympathize with how upset one can get because of problems with one's car. I feel downright depressed at times when something's wrong and fixing it seems insurmountable.

[Tleg93]

The reason I deleted the post was because I mentioned a name in the post and it offended that person. I didn't feel that you were condescending at all. My mounting bolts were in poor condition and so were the threads in the female end. They were rusted bad enough to give a false reading on the torque wrench. That's what I meant about having common sense when it comes to such things. I happened to have rushed through the process. If you have rusted bolts and holes I guess it is best to take your time and replace the problem area. In my case that would have to be the whole hub assembly unless there is a way to clean those bolt holes out. I tried cleaning the corrosion off of the bolt but in some areas it was bonded to the metal. The car must have sat in high water because the oil pan, Y-pipe, and rocker panels are all rusted.

[vrg3]

It may just have spent a lot of time in an area where salt is used heavily during winter. That can cause a lot of rust and corrosion.

Like I suggested before, a tap can go a long way towards cleaning a threaded hole out, especially if the hole goes all the way through to the other side (since the chips can fall out the other end). You can also get a "thread file" which is some kind of file with a tooth spacing that matches your thread's pitch. I've never seen one in person though.

Sometimes I clean out internal threads by just getting a stainless bolt that threads into them, coating it with motor oil, and slowly threading it in until it's a little difficult, then taking it out and blowing brake cleaner and/or compressed air into the hole, letting the brake cleaner dry, and repeating.

But if the threads are actually rusting apart (as opposed to just having a small layer of corrosion on the surface) you're right... you'd need to replace the part.