CAS o-ring change, and cam gasket

[Ricolas]

There's oil around the place, and the finger of doom is pointing at the CAS o-ring.

Time to replace it. Not that tricky a job, I managed it and it was the first thing I have done on the engine!

You will need sockets, 10, 12 and 14; torque wrench, pliers.

(I should add that this car is a standard UK '91 MX5 1.6)

1
Sparks out. You'll need a socket extension for this as they are buried in the head between the two camshafts! Remember to hold and pull off the cables by the rubber plug bits, not by tugging on the cables themselves! Remember where the HT leads go!

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2
Unplug the CAS and the coil pack. In the case of the 1.6 this is 3 connections.

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2a
unbolt coil. Top bolts - easy peasy

3
bottom coil bolt - not so easy! Fiddly, but doable.

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4
move coil - in the case of the 1.6 I moved it to the passenger side of the engine, and left it there tucked out of harms way

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5
remove PCV positive crankcase ventilation. Pull it, pop! out it comes.

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6
remove breather pipe from air intake pipe. Move clip using pliers to loosen and slide it up pipe.

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7
undo 11 cam cover bolts.

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8
cam cover off, care not to drip oil on timing belt. So move it across the engine bay, not forwards over the belts!

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9
Silicone off. Scrapey scrapey. Stanley blade useful here. You'll find it in the corners by the humps where the cam passed through to the timing cogs, and the CAS. If it is there, you'll see it, if not, you'll wonder what on earth I am on about...

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[Ricolas]

There are less photos here, as my phone was dying - so I hope to get a couple from elsewhere. In the meantime, this will be mainly written.

10
mark CAS. If your CAS is anything like mine, you'll need to clean it off first. Spot of degreaser, or just a decent wipe with an old rag. Permanent marker'll do. You *could* scribe the metal, but if in future you need to adjust the timing, how will you know which mark is which? So pen is easier here.

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11
undo CAS bolt underneath its body. This is also what you loosen to adjust the CAS angle and thus the timing.

12
CAS pulls out backwards. (It has been pointed out that there is another option here, which would appear to be easier, which is to undo the upper bolts of the bracket that hold the CAS in place, which is easier, and avoids pinching the new o-ring as you put the CAS back in.)

13
remove o ring where it is, or get it out and do it. Now I fiddled around and got the thing right out and gave it a bit of a clean. However it was a bugger to get back in again. So on balance doing it where it is works nicely!

14

The o-ring on mine was slightly flattened - obviously worn, obviously no longer providing a good seal. It snapped as I levered it off with a small screwdriver.

15
new o ring on. Spot of oil on the rubber to help it get in again.

16

The CAS will only fit in one way to the cam due to two different length lugs. These will move when you take it off so you have to fiddle around with it to get it to fit back on again! Some people use a mirror to see where to put o ring. Actually you might well be able to see the groove in the end of the cam where the CAS lug fits in. I was lucky and could, so did it that way! Look closely at the end of the camshaft and you will see the metal lug of the CAS a different colour

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17
push CAS on - bit stiff due to new o ring. Line up your marker. Tighten up the CAS mount bolt.

18
remove old cam cover gasket

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19

silicone sealer - your choice. I asked around here and some don't use it. I reckon that Mazda may have got it right in the first place, so don't bother. I did not do it, so have no pictures!

20

tighten up cam cover. ALUMINIUM!! You will strip the thread in a moment, so please, either be careful or use a torque wrench. And it is not tight - 8nm.

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21
high tension leads - back on in the order you took them off! If you cannot remember how to do this, take a picture on your phone first. No mistakes possible then.

[Mazda Mender]

I feel a sticky coming on again Mr mender, but you'll need to do it all over again with the lack of pic's
Well done Ric
M-m

[Ricolas]

PROBLEMS

I of course managed to nearly screw up by wiping off the marks on the CAS. However they were just visible, thank god.

The car would not start once I had finished. Cue much wailing and panicking here. However, calm calm. I checked the fault codes with BinaryPunk's marvellous reader thingy, and it said it was a code 3. Basically no signal from the CAS. So I cleaned the electrical connections with switch cleaner (servisol 10 from Maplins, keep it around for my guitars!) and bingo. Started, and running again!

[paggers]

Good write-up. One thing to add - not sure if you did it this way or not - but rather than pulling the CAS out the back if you unscrew the two bolts that hold the 'bridge' in place over the top then that lifts away and you can lift the CAS out. That also means that when replacing you don't have the fiddle of trying to push the CAS in and risking pinching the O-ring.

[Ricolas]

Sounds like a good plan, Paggers. I wonder why it is not recommended more often - is there a drawback to it I wonder?

[Mazda Mender]

Far easier to remove the bracket, i also recommend doing it this way for the very reason paggers mentioned about pinching the O'ring and damaging it which will mean replacing it again much sooner again then you need to
M-m

[Ricolas]

I will go and edit and put that in as a suggestion!

[flea]

I'll delete my post that's right in the middle of your pictures
i'll post it below so i dont get pulled up.

[flea]

[Ricolas]

Hey - it gave me heart as I was only half way through and realised the photo shortage!

[Mazda Mender]

Hey - it gave me heart as I was only half way through and realised the photo shortage!

I 'm sure one of us can add in the missing pic's, but it WILL be locked into the new how to section with your name all over it richard for others to follow and use keep them coming mender.
M-m

[Yolo]

Excellent post and a lot easier to do with the CAM cover off. I also removed the top bracket which lets you just lift out the CAS and drop it back in without any hassle. I may have a pic at home of it removed so everyone can see.

Well done deffinately another mender in the making!

[Tangoman]

Nice write up, I shall need to do this soon on mine!

[nobow]

Good write up, nice work.