Corolla steering question

[Corolla 1.8]

The other day on my way home from work, my 81 Corolla liftback started to pull to the left somewhat. Not a great amount, but noticeable. Also, a sound kinda like a rumbling that sounded a lot like a tire going down. I stopped sure that I had a flat, but all tires were fine. I assumed that it was a problem with the road. This morning, the same thing happened. The pull and the rumbling. I continued on and everything went back to normal after a few seconds. Everything in the front end seems to be tight. I installed new idle and pitman arms right after I bought the car. Just wondering if anyone else has ever had a similar problem. Is this something that Corollas do sometimes?? I am thinking it might have something to do with the power steering. All comments/suggestions appreciated.

[Limnos]

Have you tried anything to pinpoint what is causing it? Does it really just start doing it on its own, or is it just when you turn, brake, start the car...? How long does it last? Does it go away on its own? I've had brake calipers go on me and this will usually cause the car to pull one way or the other. Often if you get out you can smell warm brakes. If it's the caliper though it would probably be long-term unless it's just starting to go. The rumbling doesn't sound good and doesn't mesh with a caliper. I wonder if that's the bearings, in which case you shouldn't really drive it. If it happens when you steer it could be part of the steering system. Try to provide more specific information or maybe take it by a mechanic.

[Corolla 1.8]

Well, first off, I am a mechanic. I have tried to get a handle on some sort of pattern. So far, this has happened twice. Both times I was running 55-60 mph and going straight. The light rumbling sound (doesn't sound anything a wheel bearing) seems to be coming from the front somewhere. Then the car pulls noticably to the left. Not to the point of really having to hang onto it, but would definitely change lanes if I were not holding the wheel. Then, just like it started, it goes away. I have driven the car all week and have had no problem. I put the car on the rack at work when I first bought it and checked all the front end components. This is when I found the bad idle and pitman arms. Everything is tight, tie rod ends linkages, everything. This is going to be a hard problem to find until it gets a lot worse than it is now. I am thinking some kind of problem with the PS, maybe a valve sticking or something like this. It never hurts to ask others with similar cars, as if it is a problem specific to Corollas, probably someone else has had it. The rotors do need to be turned, as there is a little shake when braking, but not so bad that it can't wait until the next brake pad replace. It sounds and acts almost exactly like a tire going flat.