Changing the Micra Macpherson struts shock absorber/spring/bearing

This car has had a really annoying knocking or rumble from the suspension ever since I got it. At first I suspected ARB drop links- a cheap and easy fix, but swapping these has made no improvement. I took the car to 2 garages to try to diagnose the fault and neither could find anything obvious. Their advice was to keep driving it until whatever is causing the noise wears sufficiently to be obvious- I'm not keen to put up with it for that long and anyway I could do with a bit more experience on a modern car.

The garages could find no faults with ball joints or wishbone bushes- or indeed the sub-frame bushes themselves but  there is a problem so it has to be somewhere, and given that its not obvious, I assume it has to be something hidden. My suspicions next fell on the struts and shocks which could be rattling inside even though they pass the bounce test and are not leaking. It could also be the ARB bushes which are hidden from sight above the front sub-frame. So moving on in my list of suspects I decided to swap the shocks and then, if still no improvement, the wishbones. Finally if that all fails I will drop the sub-frame and check the ARB bushes, but this is a job I am not keen to do.

Access to the strut top bolts requires removal of the scuttle panel in front of the windscreen and to start removing the struts I was recommended to disconnect the battery-oops I don't have the radio code! In fact there's not much danger of shorting anything so if doing it again I might not disconnect.

 The scuttle panel is held on by clips through the rubber strip at the front

Several of the clips pulled out of the rubber but they are easily reinserted.

The windscreen wipers also attach above the scuttle so these need to come off

Detach the cap and unscrew the nut

use a puller to remove the arms

The scuttle then pulls forward and can be slid sideways to  unclip the sides before coming out. This exposes the front and fragile lower edge of the windscreen but also lets you get at the third strut mounting nut

3rd strut nut now revealed each sdie

Draw around the three top nuts with a sharpie so that they can be put back in the same place and maintain camber

Jack up the car- I lifted under the front subframe each side before lowering it onto some axle stands with pinch weld slots in their pads.

Pinch weld pad on axle stands

Remove the road wheel the strut is then visible and you can see the two beefy M12 bolts holding the strut to the steering knuckle/hub carrier.

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The strut also has clips for the antilock brake wiring (2 rubber grommets) in the front and the flexible brake line at the rear

The anti-lock wiring just pulls out, it helps if you rotate the grommets a little first

The brake line clip is likely to be dirty and rusty so I wire brushed it and treated it to some penetrating lube

You can tap the clip down with a screwdriver and hammer, the brake line also looks a bit grubby so more cleaning and probably a little anti-rust treatment will be needed.

Remove the nut from the top ARB drop-link. Fairly easy as I've just changed these.

Now remove the two bolts holding the strut to the steering knuckle, noting that they are inserted from the front.

This was where I hit the buffers! All sources I can find just say remove the nuts... but the K12 has a different type of nut. At first I thought it had actually been welded in place because of the metal tabs protruding locking it to the thread. However I can see nuts like this throughout the front suspension and in fact Nissan have used here a type of all-metal self-locking nut termed a Staytight or Stiffinox. I was hoping that there is a trick to removing these, but it seems there isn't and its simply a case of using a lot of force. I'm not happy with this and even if I can shift the nuts, they obviously will not survive the process. I had therefore to call a halt at this stage whilst I investigated a source of fresh nuts and bolts.  I will probably need new wishbone mounting bolts too so I sourced those as well. Seems hard to find these from online parts suppliers. Bit disappointed here,  they are not slow to sell you the wishbones and struts but few want to be bothered with the bolts which I think is a cop-out. You can get them from Nissan but they are fairly pricey; the wishbone bolts being over £6 plus VAT each. I paid £40 for strut and wishbone bolts- which arrived without nuts, so another £12 getting 8 nuts. You may be able to get them cheaper, they are after all not magic, they are just  M12 extra fine thread (1.25 pitch) bolts and you can replace them with bolts of a suitable grade. The strut bolts and the forward wishbone mount are loaded in shear... Ie across the bolt and grade 10.9 is used here. The rear wishbone mounting is loaded in stress and a superior strength marked 11.9 is used here. You will need  grade 10 nuts from an engineering supplier obviously of the same thread, I found these were more easily available as flanged nuts.  You will need 4 x 6omm, 2 x 90mm (grade 11.9) and 2 x 130mm bolts. The original nuts and bolts were both flanged nuts so you will need 2 large washers per bolt and one spring washer to lock the nuts in place. Alternatively you could use nyloc nuts instead of the spring washer. I ordered the appropriate nuts and bolts which to my surprise aren't stock items at Nissan so I had to put the car back together whilst I waited for delivery.

When  these had arrived I was able to quickly strip down to the stage reached previously and this time I simply used a breaker bar and long-ish ratchet handle to loosen the bolts- yes it took quite a lot of force but they did unscrew and surprisingly did survive the process.

Breaker bar and long ratchet to loosen the two strut-t-knuckle bolts.

Next I loosened the three top nuts holding the strut - the outer front nut is awkward to reach as its under the headlamp bracket. Release the headlamp screws  and the bracket can be moved over to access the nut.

Loosening the front strut top bolt once the headlamp bracket is loosened.

I also loosened the strut top nut using a breaker bar. There is a tendency for the whole strut to turn although this is reduced if the strut is still fixed to the car. I found it helped to put a sharpie mark across the thread and nuts so that I could check that the nut was loosening rather than simply rotating with the strut. However its important NOT to unscrew this nut completely or you may be injured when the strut is released.

I could then remove the strut to steering knuckle bolts which were loosened above, and then remove the three strut top nuts. I started with the most awkward nuts first- removing the rear mounting bolt first and using a magnet to retrieve the bolt.

using a magnet to retrieve the rear strut top bolt

I could then remove the front right (behind the headlamp bracket) and lastly the easily accessed front right nut.
This releases the strut to hold the strut as you remove the last bolt and then fineagle it out from under the wing.

The strut as removed didnt look too bad but had clearly seen better days with corrosion well established around the lower extremes.

Strut removed from the car

I used Sealey spring compressors to compress the spring

Fitting the Sealey spring compressors

Once the spring tension was controlled I could remove the strut top nut completely. I used a through the centre socket and a Torx key inserted into the top of the strut through the socket to prevent that from turning. Since I had loosened the nut already this wasn't too tricky,

Using a Torx key through the socket to hold the strut whilst turning the nut

 I unscrewed the nut completely, and could then remove the nut and top cap/bearing assembly

Top cap bearing assembly removed.

Old and new

This is the old and new top cap/ bearings compared. I couldn't find any obvious wear ion the old ones but given I'm chasing a hidden knocking these do qualify as candidates so I intended to fit new ones anyway. Note Both shocks and strut top bearings are handed so make sure you fit to the correct side. I think the strut bearings will only fit one way round but if youve put the left hand bearing to the right hand shock...

The new shocks arrived with w wire restraint for transit. Compress the strut to loosen the restraint and remove it from the strut.

New strut transit wire

To start the reassembly process, I first selected the correct strut because these are handed. I could then prime the shock by holding it steady and vertical in the correct orientation and pump it fully up and down 3 times.

Compressing the shock absorber to prime the oil/gas

I

New strut with bumpstop rubber, compressed spring placed in position

I could then slip on the new dust cover/bumpstop, slip the still compressed spring over the strut (engaging the bottom with the spring stop cast into the support cup) and finally replace the top-cap/bearing. I could then fit the new top nut again using the Torx key to hold the strut through the through the handle socket, I didn't do it up too tightly, just enough to hold everything together.

Top cap done up loosely to control the spring before the compressors are released.

Finally I removed the compressors leaving the spring in place (again check the end of the spring does locate against the end-stop cast in the strut dish support- there is no end-stop in the top cap. 

Newly assembled strut ready to be fitted.

Refitting the strut was the reverse of disassembly and was quite straight-forward but I will make the following suggestions:

1. When you introduce the strut the brake pipe passes behind it and the anti-lock brake wire passes in front of it.. 

2. When refitting the three top bolts its necessary to make sure that their heads fit into the outlines drawn on the strut top before disassembly. This will maintain castor angle. However, these three bolts take a lot of stress during fitting and removal and their threads seem to get damaged. If they bind in their holes then tightening them will always move the strut out of alignment. I had to chase the threads on all three with a die so that I could screw them in easily. 

3. The strut top-cap will only fit in one position, align it and hold it in place loosely with the easiest of the top bolts to access first before working towards the hardest checking that the bolt heads remain in their correct position

4. I didn't tighten any bolts to their required torque until the suspension was under load. However, to preserve access I couldn't really refit the wheel and lower the car. I used a trolley jack to raise the lower wishbone and stress the suspension whilst the car was still on the axle stands before tightening any bolts. I tightened the strut-to-knuckle bolts first, followed by the drop links and then the three strut-top bolts. Finally I could re-tighten the strut top nut using the Torx-key-through-socket approach and a torque wrench to complete.

5. Checking out You-tube for this job I saw advice to check that the spring is the correct way up when you refit. That was for a K11, but as far as I can see the spring will only fit one way up in this model.

Remember to refit the anti-lock brake wire grommets and brake hose clips

Finally, I could refit the wheel and lower the car.

New strut in position

... So has it helped with my rumble?? The jury is still out, its possibly better but I will have to change the other side and possibly the rears before I can be sure that the shock absorbers were really the cause.