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MK1 NA 1.6/1.8 89/97 CAS O'ring and rocker seal replacemnet

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MK1 NA 1.6/1.8 89/97 CAS O'ring and rocker seal replacemnet

Postby Mazda Mender » Fri Sep 23, 2016 7:36 am

This is a guide on replacing the CAS O'ring which is the same procedure for the MK 1 1.6 ( On the left hand side rear *1 ) and 1.8 ( on the right hand side rear **2) versions be it a Jap Eunos import, stateside Miata or European Mx5 from 1989 to 1997, we do recommend that you also change the Rocker seal at the same time as that will be as old and worn/dry as the CAS seal.

****** Don,t do this straight after the Mazster as been running, it needs to be done when the engine is cold ******

For this guide we will be using a MK 1 Eunos 1.6 NA....

This job should take around 45minutes...

*1....Mk 1 1.6....CAS on the left, coil packs/bracket on the right

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**2...Mk 1 1.8.... CAS on the right,coil packs/bracket on the left

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Parts needed...

1 x O'ring seal
1 x cam rocker cover seal ( please use OE Mazda seal for this as the aftermarket ones will weep oil again after a short period of time 100%)
Sealant only if you have removed all the old stuff.

Tools needed.....

1/4 drive ratchet, and extensios
1/4 drive 10mm socket
3/8 drive ratchet and extension
3/8 drive 12mm socket
1/2 drive ratchet and extension ( only if a strut brace is fitted and needs removing )
1/2 drive 14mm socket ( only if a strut brace is fitted and needs removing )
12mm flat ring spanner
paint pen or similar

*****Please note :-MK 1 1.6 NA is being used for this how to guide, 1.8 is just a mirror image *****

So to the job in hand, this is a a fairly easy straight forward job to do for the home/drive way spanner thrower, in this how to guide we will not be doing this without removing the cam rocker cover as some guides out there show, some times.... "more is less", doing this job without removing the cover is more awkward and a lot more fiddly, but the most important part is that when you are struggling to get it back in the bracket in the confined space and trying to guess where the lining up the fl wheel into the cam slots it pinches the O'ring seal. This does not make a proper seal resulting in oil weeping again with in a couple of months and you have just wasted your money and time and need to do it all over again but this time correct. Personally I am not in the habit of wasting my time and cash ( maybe the scotch blood in me)and it is a case of done once, done right forget about it for many years to come, or is it just me????

WE will assume that you have a engine strut brace just for this guide so get you 1/2 " ratchet/extension and 14mm socket to undo the 4 x 14mm suspensions top mount holding nuts..

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Once the strut brace is removed if fitted, you now need to remove the coil pack frame from the rocker cover by way of the 3x 12mm that hold it in place 2 at the top and one you will love below but hidden, it makes no difference if it is a 1.6 or 1.8 version they both are held in place by 3 bolts, what Iwill say is once you remove the botom back 12mm bolt ,you don't need to put it back, so get your 12mm ring spanner( don't try it with a open flat) it will be tight so watch those knuckles, a knuckle ratchet spanner will help once you have cracked it as it is all touch, once removed get the 3/8 ratchet, extension and 12mm socket to remove the two 12mm head bolts holding the top of the bracket to the rocker cover, once they are removed unplug the HT leads from the spark plug wells only and just push the coils and pack to the back, there is no need to remove it from the Mazster for this job...

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Pull the hose off the breath valve and from the air trunking that runs to the rocker cover..

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Unplug all the electric plugs and leave them to one side...Clean the CAS bracket and body of the CAS while the rocker cover is still in place which will stop and dirt falling into the top of the engine and mark it up in 3 places, both sides and dead top, this will give you the timing marks for when you refit it so everything still runs sweet.

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Now you will need the 1/4 drive ratchet, extension and 10mm socket to crack and remove the 11 x 10mm head bolts that hold the rocker cover in place ( use a lid of one of the spray lubes to act as a "keep safe")..

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Crack and remove all the bolts and keep them safe...

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Once removed, lift the rocker cover off,( lift and twist sharpish as oil will drip from underneath) rest it out of the way somewhere safe on something upside down, and put a piece of plastic over the underside to stop and kind of dirt blowing into it.

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Now we need the 12mm ring spanner and 3/8 ratchet, extension and 12mm socket again...crack the 12mm on the back first and remove, then the 2 x 12mm bolts that hold the bracket, put the bolts in the lube lid safe ;0)....

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Once the bolts are removed, take the holding bracket off and put it somewhere safe and remove the CAS from the cam shaft and head,,,give everything a wipe down....

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Get yourself a pick etc to remove the old O'ring from the CAS, in 95% on doing this it will be so old and dry that it will just crack into pieces as you try any way, throw the old seal away and clean the rest of the CAS up read for the new seal, now some put the seal on dry and some wipe a bit of fresh oil on where the seal sits...personal choice here on that one,,,put the new seal on ready for fitting....

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And then it is just down to refitting, slot the butterfly lugs into the back of the cam shaft, put the holding bracket back in place and the 2 x 12mm bolts but only finger tight for the minute, put the rear 12mm adjuster bolt back in finger tight, move the CAS until it lines up with the timing marks you have added, push the CAS at the back so it becomes flush with the head and bracket and tighten down the top 2 12mm bolts and then once tight, tighten up the 12mm adjuster bolt too.

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Now it is just a case of removing the old rocker seal while it is upside down again using the pick if needed, if like the one of this roadster it was that old and dry it was snapping for fun, replace only with a OE rocker seal as the aftermarket ones are rubbish....

Old and new...

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Re fit everything back together as removal...as for the rocker cover bolts, there is a routine on tightening up, do not go off the torque settings on line or in the haynes manual....otherwise you will snap bolts from that info and advice...

There is also a big who cares about automotive sealant in the corners,,,,,IF you have removed all the old factory blobs on the head then it is recommended to apply fresh before putting the cover back on, ,,,if it is still there and you are using a OE Mazda rocker seal then you will not need to remove the old and replace with new...Drop the the cover on the head, drop all 11 x 10mm bolts in the correct holes, start them off by hand, get you 1/4 drive extension and 10mm socket and turn them all in with just hand pressure , snap in you 1/4 ratchet and start to tighten up following the sequence below to just "tight" once you have reached the end of the sequence go back to the beginning and run over them again...our torque setting is.... tight, baby grr(Nip up) and that is all it needs...

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Put your pipe for the breather valve back on and at the the inlet trunking, coil pack back on, HT leads in , electric plugs and sockets back together, strut brace if fitted, start her up and get out in her.
As always anything you are unsure of, please just ask, it's what we are here for.
The Disclaimer:-
This post is a natural product made from recycled electrons. The slight variations in spelling and grammar enhance its individual character and beauty and in no way are to be considered flaws or defects, the articles/answers/comments are provided for information purposes and they are not intended to substitute informed professional advice, I or mazdamenders.net cannot personally be hold responsible for any damage occurred from following this procedure or any injuries from it. Proceed at your own risk.

Mk 1 Eunos 93 black V.S II 1.8 fettling,
Mk 2 .1/4 Roadster 99 black & gold V.S 1.8 being rebuilt,
Mk 1 Eunos 90 1.6 (claimed by daughter)
Mk 1 Eunos 96 1.8 blue B2...being fettled
Mk1 Eunos 93 1.6 black S special **gone**
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Re: MK1 NA 1.6/1.8 89/97 CAS O'ring and rocker seal replacemnet

Postby storm » Thu Sep 29, 2016 9:24 pm

Made the mistake of thinking that i could do the CAS seal on its own by just pulling the CAS,... 2 months later it's leaking. When fitting it back (even with a dab of oil on tbe ring) the ring gets pinched just enough to start leaking.

This is the only way to do it right.

Thanks Wayne
1. A car is only worth what someone is willing to pay for it, 2. Resale wont save your life in an accident, 3. Genius has limits, stupidity has none, 4. Never argue with an idiot, they will bring you down to their level & beat you with experience, 5. Growing old beats the alternative -- dying young!

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