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de-powering a MK1 power steering rack

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de-powering a MK1 power steering rack

Postby Mxmurray » Sat Nov 18, 2017 1:43 am

Tie rod.jpg
Tie rod.jpg (305.6 KiB) Viewed 908 times
Rack lock ring.jpg
Rack lock ring.jpg (240.97 KiB) Viewed 908 times
Rotary Valve.jpg
Rotary Valve.jpg (261.24 KiB) Viewed 908 times
Pinion TIG welded.jpg
Pinion TIG welded.jpg (349.21 KiB) Viewed 908 times
Pinion detail.jpg
Pinion detail.jpg (257.28 KiB) Viewed 908 times
De-powering a Mazda MX-5 Mk1 Power steering rack

There has been plenty of articles written about the Mk1 Power steering, some say it’s too light for spirited driving, giving the car a wayward feel at speed, some say the way forward is a standard non-powered steering rack.
Other people seem to think de powering a power steering rack will give the best of both worlds, you gain more feel over the powered rack but gain the quicker action.
The power steering rack has a quicker ratio than the non-powered rack theoretically making it better for spirited driving.
I use my MX-5’s for Autosolo’s and I can cause the power steering on my MK3 MX-5 to struggle with a slalom it just won’t turn as quick as I want it to so I don’t want the same situation on my MK1.
How this works on a daily driver I don’t know, but will soon find out as that what this article is all about.
Firstly there are some decent videos on line showing the removal of the power steering rack from the car so I won’t go over that here.
A quick search shows a number of instructional videos, the rack is basically held to the body of the vehicle by two “U” shaped brackets, and the other ends are connected to the hubs via tie rods.
Mark the tie rods where they meet the balljoint to ensure on refitting you get the rods back to somewhere close, you will need to have the car aligned correctly following this work so if you have to drive the car on the road please get the measurements as close as possible before disassembly and try to get them as close as possible on reassembly.
Once the tie rods are split from the hubs, the two brackets can be removed, you will have to undo a couple of the pipes from the rack to the power steering pump before the unit is released from the car.
Once the unit is free of the car, give it a good wash; get rid of all the accumulated road grime and oil to make it nicer to work with.
Get the rack on the bench and following one of the instructional videos strip it down.
1. Remove the tie rod boots
Easy to do as they are held on with either cable ties or tie wire, if the boots are split bin them and buy a new set.

2. Remove the tie rods
Tie rod.jpg
Tie rod.jpg (305.6 KiB) Viewed 908 times

Looking at the naked steering rack you will see the tie rods are attached to the rack via a cylindrical nut with four flat surfaces, and on each of those flat surfaces a flat lock washer has been tapped over to lock the tie rod to the rack. Tap those washers out to allow you to undo the tie rod from the rack, do this on each side. Place the rods to one side as they will be reused.

Remove the adjuster nut
3. Now looking at the rack you can see where the steering column is attached to the rack by the splined end protruding from the raised pinion housing and at the bottom of that housing you will see a rather large nut with a smaller nut inside it. That is the adjusting nut for the rack, the outer nut is a locking nut which may take some getting off and then remove the smaller cap to reveal a spring, a washer and a shaped adjuster. Remember how they all came out and ensure the all go back in the same order, put all these items to one side, they will be reused.

Removing the Pinion
4. Working underneath the rack you will see a 21mm nut, undo this and remove the cap, and then you will see a 17mm nut, undo this nut and put both to one side as they will be reused.
At the other end of the pinion you may find a dust cap, pull it off the pinion and place it to one side, if it is damaged bin it and replace it with a new one, under the dust cover you will see a circlip, remove the circlip and place it to one side it will be reused if it is in good condition. Now the Pinion should pull from the housing up in the direction of the circlip.
Put the pinion to one side I will go into that more in a moment.
There is a bearing at the opposite side to the circlip, check this and you know the score, if it is fine set it to one side it will be reused, if it is knackered replace it. The bearing will almost fall out of the housing as it is not an interference fit.

Removing the Rack from the housing
5. You should now be left with a rack minus the pinion and can see both ends of the steering rack itself, to remove the rack look at the rack opposite the pinion and you will see and end cap and if you look closely you will see a small lock ring, to remove this ring Mazda kindly cut a slot in the rack to allow a small pick to be inserted which flicks the ring out, put it to one side etc etc. The rack can now be removed from the housing by gently tapping the opposite end with a “SOFT” mallet, do not use a normal hammer as you will damage the rack or pull on the rack from the end you have just removed the lock ring it should just slide out. The lock ring is located on a rather large bushing which will pull out with the rack put it to one side etc etc. You will now see one of the reasons we have delved into the rack.

Half way along the rack itself you will see a metal ring with a seal inserted, this needs to be cut off the rack, this ring is to push the power steering fluid along the housing when you operate the steering wheel, and as we won’t have fluid we don’t need the ring.
Make a few cuts in the ring at 90 degrees to the rack and the ring should fall apart and come away from the rack.
Once that is done place the rack to one side etc etc.

Now turn your attention to the pinion we removed earlier.
Looking the pinion you will see it has a rotary valve and is held on with a circlip underneath, undo the circlip and remove the rotary valve and bin it, we won’t have fluid so there is no need for the valve.
You should now be looking at a bare pinion and half way down the pinion you will see a white silicone seal, pry this out and the black “O”ring under it, these seals can be binned.

Now a lot of other de powering guides leave the pinion as it is and once the ring has been cut off the rack they build it back up and leave it at that. But if you carefully grip the pinion in a soft jawed vice and carefully grip the other end with soft faced grips and twist you will see a slight movement, this movement is to compensate for the power steering fluid when the steering is in use. As we will not have fluid we need to weld the pinion to remove that play.

If you look down the pinion shaft you will see where you removed the “O” ring this is where it needs welding to make the shaft a solid piece (it’s too late for me to make jokes).
I had mine TIG welded as I didn’t trust my own welding but I’m sure MIG welding will do just fine, just make sure no welding spatter gets into the pinion teeth.

Once all the welding has been done and the ring removed from the rack we are ready to rebuild the rack.

Everything I told you to keep can now be refitted but make sure plenty of grease is applied to the cleaned inner workings of the rack including the pinion teeth and rack teeth.
Ensure the rack adjuster is adjusted to allow smooth movement of rack and replace the tie rods and tap the lock washer back ensuring all four tabs are tapped into place.

Whilst we have the rack open if you are into drifting and want more steering angle then now is the time to place a spacer between the steering rack and tie rod ( these can be bought from various outlets) otherwise refit your new boots and lock them on using the fittings that came with them.

The only thing left to do no is seal the holes where the pipe work entered and exited the rack, this will stop any grit getting into the rack so make it last longer.
There are various methods used to seal the holes in the rack from using epoxy resin to removing the unused pipe from the fitting then welding the end of the fitting and replace those in the rack to chemical metal used to seal the hole, just ensure no chemical stuff gets into the rack and causes you problems.
Whichever route you take to seal the holes ensure they are sealed properly so no grit can get in.

The rack can now be centered by turning the rack all the way to one side then to the opposite side and once you have done that count the number of full turns the splined shaft makes from one side to the other and simply half that number for the centre of the rack and turn the splined shaft that amount, So if your lock to lock is three turns then the centre of the rack is 1.5 turns. Set the rack to centre before fitting it to the car and replace the tie rods.
Once the rods have been refitted and the boots replaced, make sure the dust seal is replaced and refit the rack to the car, drive slowly to have it aligned and then marvel at your direct steering.
Tie rod.jpg
Tie rod.jpg (305.6 KiB) Viewed 908 times
Pinion housing adjuster location.jpg
Pinion housing adjuster location.jpg (305.18 KiB) Viewed 908 times
Adjuster bush.jpg
Adjuster bush.jpg (249.31 KiB) Viewed 908 times
Left over parts.jpg
Left over parts.jpg (349.2 KiB) Viewed 908 times
Last edited by Mxmurray on Sun Nov 19, 2017 12:36 am, edited 5 times in total.
Serial Poster
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Re: de-powering a MK1 power steering rack

Postby Mxmurray » Sat Nov 18, 2017 1:44 am

I did record a video covering all the above but managed to delete it from my phone when attempting to be a clever git I will try post some pictures to go with the above.

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