Noise from the power steering mechanism on uneven surfaces

[Vadim]

Want to share experience of a workaround to fix noise in the power steering mechanism.

The noise appears when driving on slightly uneven surfaces with straight position of the steering wheel. It often happens in older RX cars due to wear of the gear in the power steering worm-gear mechanism, and because the metal ring which pushes the "worm" axle to the gear is weak and has very limited travel. When the steering motor does small movements back and forth to reach the worn gear it causes the noise / vibration.

The problem can be resolved by adding a small coil spring to push the bearing of the "worm" axle to the gear a bit more.

The spring I used was 8mm external diameter from 0.8mm wire, ordered on e-bay. It only needs 2-2.5 turns of the spring. Mind that there must be a tiny bit of travel to let the "worm" go over less worn parts of the gear.

The access is very tight, and the steel cover is difficult to remove. I had to unscrew the driver's seat to move it 10cm further back (without disconnecting) to get proper access. Other than that you just need to remove the plastic cover, which holds over the gas/break pedals (two screws and a couple of clips).

To open the bearing cover I had to gently hammer a small victorinox knife blade between the cover and body. Once it moved 0.5mm, it will fall out of its place easily. You will need tiny pliers to compress the new spring and insert into the dedicated gap between the bearing and the housing. The levers of the original ring-spring may be cut to give more space (it is made of soft metal, so even if you try to mend it, chances are you'll have to revisit it).

Photos:
1) the worm-gear of the power-steering mechanism (this photo is from Prius, not the RX, but it gives a good idea what to look for; it is much more crowded there in RX)

2) removed plastic cover

3) the actual bearing of the worm and the coil spring inserted into the gap. The levers of the original ring-spring, which occupied this place were cut off. The ring-spring and the rubber ring on top of it may be removed to give better access when inserting the new spring. On this photo you can see a half of the inserted coil spring, while the other half is already covered by the rubber ring. The bearing is pressed onto the axle, so don't be afraid that it will fall off when operating near it.

4 and 5) the remainder of the coil spring

In my car it helped to kill the noise completely and 7k miles later there are no issues. If/when the noise reappears due to more wear to the gear, the steering column will have to be replaced.

If you have experience with this type of jobs, it may take about 40 min altogether with all precautions.

Mechanical skills required: above average.

 

[Barry14UK]

Useful to know - thanks for posting.  How quickly this may be needed will vary due to several things but would be interested to know approximate  mileage  need for this mod was noticed on your car. 

[Vadim]

10 hours ago, Barry14UK said:

Useful to know - thanks for posting.  How quickly this may be needed will vary due to several things but would be interested to know approximate  mileage  need for this mod was noticed on your car. 

I bought the car with this issue when it was 184k miles (2011 reg). I'm sure the steering column was not replaced or repaired before, so it is quite a mileage )

This issue may often be a reason for sale, because when the previous owner starts to worry about the noise, dealer asks over £2k for the replacement.

It is just one of the weak spots to look for in older RX.

[Barry14UK]

Thank you.  I will not be doing enough mileage in mind to encounter this problem I think but for owners who may do so might bookmark or note this fix to avoid premature sale or high cost of fixing at some point.