Quote:
Originally Posted by radroach
Since this is a Toyota power steering unit, I wonder if there are any other car models affected, like the prius.
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The Prius certainly has a spate of power steering issues - in fact the reason I'm here is to decide what to replace my Prius with. Looks like the hachi-roku just went off the list. Maybe I'll just buy a Buick Electra 225 and have a shop restore it. Cheaper than a new car...
Anyway, the Prius unit is the "inside the steering column" type. It uses a motor-driven worm gear to turn the steering wheel, a position sensor to see where it's pointed, and a rotary strain gauge to tell how hard the user is trying to turn the wheel. Notice I said "user", not "driver". Anyway.
Two common failure modes:
One is that the car suddenly starts trying to fight the turning of the wheel, and does so in pulses of about two per second. This is probably a failure of the position sensor. It makes the car basically undrivable - it isn't a bad idea to carry some wire cutters so you can snip the wires to the motor so you can limp home. At least it won't do this below 10mph, so you can crawl home.
The second failure mode is the worm gear itself. The steel worm gear is retained by a pair of bearings held into position with springs. Over time the springs will fail and the worm is no longer positioned positively. This causes the steering wheel to "chuckle" going over the slightest bumps. Eventually it will allow so much motion that the plastic gear the worm turns against will strip. Yes, the driver's life (potentially) depends on a plastic gear in the power steering. Anyway, it's a $USD 2200 part and the labor to get to it is... non trivial. There is a workaround. If you're persistent, you can get the end cap off of the housing that holds this abomination together. Grind a wedge about 3mm thick and maybe 4-5mm thick on the other end. Hammer the wedge in between the bearing and the housing. Button it back up and drive on. I'm told it will last about 6 months. I'm wondering about a combination of The Wedge and some epoxy putty. I'll just have to be really careful to keep the epoxy out of the rotating assembly.
You know what really worries me? The Prius has two idiot lights on the dash. The standard MIL (Malfunction Indicator Lamp, quoting FMVSS, but colloquially the CEL) indicates powertrain / emissions problems. The Red Triangle indicates any other failure. The 86, on the other hand, has a special, dedicated light that means "the power steering just failed". How did Toyota know this was going to happen enough to need it's own idiot light? Some engineer had to think "this is going to fail so much we ought to at least put a special warning light in there". I assume there's no warning light for "you need new wiper blades" or "the cylinder head just cracked", but it has one for power steering failure. Curious.
(I've heard every prius joke. It gets 48 mpg with the air on, the 200V battery will run a guitar amp directly for barn parties with no hum at all, and my el camino isn't exactly a daily driver. I'll miss running the amp without a mile of extension cords, but replacing the steering servo will wipe out anything I saved on fuel. )