Mazda MX-5 Miata banner
Status
Not open for further replies.
1 - 6 of 6 Posts

·
Oh, hai!
Joined
·
5,001 Posts
How to: Change the Cam/timing belt

Please read this guide in its entirety before picking up any spanners. Skipping ahead or rushing could cause you problems further down the line.
Please also note that this was carried out on a '95 1.8 Eunos. Items may differ from earlier 1.6s or later Mk2/2.5s, although the actual cambelt should be identical.
Where possible, I have commented on possible differences.

When does it need doing?
Every 60,000 miles. If you don't do much mileage, replacing it every few years or so would be wise. Some owners change theirs earlier for peace of mind, although the MX-5 engine is non-interference and the pistons won't touch the valves unless you're at the redline when it lets go and incredibly unlucky.

What do I need?
Cambelt kit (Cheapest place I found was MX5parts, but shop around)
Sockets/spanners - 10mm, 12mm, 14mm, 21mm
Phillips/flat head screwdrivers

Torque Settings (Source: Haynes manual)
Spark plugs - 15-22Nm/11-16lb.ft
Cam cover bolts - 6-8Nm/3.5-6.5lb.ft
Cam belt cover - hand tight
Water pump pulley bolts - 8-11Nm/6-8lb.ft
Cambelt tensioner/idler bolts - 38-51Nm/28-38lb.ft
Crankshaft pulley bolt (early short nose 1.6) - 108-118Nm/80-87lb.ft
Crankshaft pulley bolt (Post '91 long nose 1.6 and all 1.8) - 157-166Nm/116-122lb.ft

How do I do it?
Firstly, the auxillary belts have to come off. If you don't know how to do this, have a read of my auxillary belt guide. Before you steam off and do that though, slacken off the 10mm bolts holding the water pump pulley on. It is so much easier doing this with the aux belt fitted and tensioned.

Here's what they look like...


After you've slackened the pulley bolts and removed both auxillary belts, finish undoing the pulley bolts and remove the pulley...


Next, undo the small spring clips securing the two water hoses to the thermostat t-piece. The spring clips are a little fragile so having some spare or some small jubilee clips would be wise. Note that if your coolant system is full you will get some coolant loss doing this so remember to top it up later when you're done.




Next up, the cam cover. Undo the two bolts closest to you holding the metal breather pipe on. Unclip the rubber end from the cover.

Remove the HT leads, marking them if necessary to ensure they go back into the same place. Removal of the spark plugs isn't strictly necessary but will make turning the engine easier later on. You can also remove the remaining 10 bolts securing the rocker cover (they're all shown below) but don't remove the cover yet.




Unclip and remove the rubber hose on the PCV valve. It's about halfway down the left of the cover and leads into the inlet plenum.


Before the cover comes off, the coil pack will need to be removed. They are held on by a pair of 12mm bolts that are a pain in the arse to get to and undo.

Here's the left one with spanner on it...




And the right...




Once undone, the coilpack can be pushed out of the way and the cam cover removed.

Wooo, oily bits!






You can see here that the cam cover gasket is fucked. This will need scraping off and replacing. You can do that now or later, it doesn't make a difference.


Next item for removal is the upper cambelt cover. It is secured with 4 12mm bolts indicated...








Make a note of the position of the cable/pipe clips attached to the right two bolts as they'll need to go back into the correct position. The easiest way to do this is to put the bolts back into the cover in their original position once it's off and store it somewhere out of the way.


Next, the cambelt mid cover. There is a single bolt for this that is located in a recess on the left side of the cover. I couldn't get the camera in there very well though...




At this point, the crank pulley needs to be removed. The nut is a 21mm one and it will be on tight so you'll need a decent breaker bar. As there is no real method of locking the engine to prevent it turning over, you will need an assistant to sit in the car with it in gear (5th) and their foot jammed on the footbrake. You might get away with it without a helper if your handbrake is epic, but I suspect not. You might also need to move the car back or forth to give you as much leverage as possible. Note that once you have stackened the nut with the breaker bar, it can be removed using a ratched but be aware that you won't be able to undo it all the way with the ratchet fitted without fouling the antiroll bar. Once the nut is undone, remove the pulley. On short-nose cranked 1.6s, wear would be indicated by a wobbly bolt or the small woodruff key falling out when the pulley is removed. If you have a worn crank nose, you need to read the guides on here as to what to do (I'll link to one when I find it!). It is also recommended to replace the woodruff key and bolt whenever they are removed (not necessary on long-nose cranked 1.6s or 1.8s).

Once the pulley is off, you can undo the remaining bolts on the lower cambelt cover and remove it. The keen eyed amongst will you will have already noticed that I did this arse backwards. It doesn't really matter, although the cover won't come out until the crank pulley is removed.

Lower cover bolt locations






Now for the fun part. Using a 14mm spanner on one of the cam sprocket retaining nuts, turn them until the timing marks are lined up as shown below. It is easier to see them if they are marked with something like Tipex or a paint pen. Be warned: Not doing this correctly will lead to timing problems later on if not corrected.



You should also note that the woodruff key on the lower pulley should also be lined up with the marking on the case behind it (excuse the brown-ness, Yuki has been leaking!)


The engine is now at Top Dead Centre (TDC).

Now, slacken off the bolt holding the cambelt tensioner pulley. This is the left one with the spring attached.


Using a screwdriver or flat bar, prise the pulley out as far to the left (towards the inlet cam) as possible, then re-tighten the bolt. This will remove the tension from the timing belt allowing for its removal. Remove the belt.

Once the belt is off, remove the tensioner pulley and the idler pulley on the other side. This is the idler prior to belt removal...


If you're replacing the water pump, you now need to read my guide on water pump removal (Link soon!). If not, continue reading...

This, unfortunately, is where the pictures stop, although you're now at the point where things start to go back together. Here is a step-by-step guide. Refer to earlier pictures if you need to know how it was before you pulled it apart.

1) Replace the tensioner and idler. Remember to keep the tensioner as far left as possible before tightening the bolt and torque the idler bolt to the specified settings.
2) Ensure the timing marks still line up. Check the pictures if necessary. It is imperative you get them right!
3) Starting at the lower pulley, place the new cambelt around it. Keeping it as taught as possible. Run is to the left side of the idler pulley then around the exhaust cam sprocket. The teeth should line up perfectly.
4) Maintaining the tension in the belt, run it across to the inlet cam sprocket. Turning the sprocket a few degrees clockwise should help to line up the teeth before turning it back. Be aware that tension in the valve springs can cause the pulley to snap around, which could injure you and fling your spanner into the ether!
5) Once the belt is around the inlet pulley, feed it around the right side of the tensioner pulley. It should now be correctly fitted.
6) Check the timing marks line up correctly. Turn the engine two full revolutions and check again. The marks should still line up as before. The easiest way to turn the engine is to put the car into 5th and pull it. You'll need about 10ft to get a full revolution. If you're lacking space, pull it as far as possible, slip it out of gear and push it back, then back into gear and pull again. Repeat until the engine has done two revolutions then check the markings. You can also turn the engine by using a breaker bar on the crank. You'll need to refit the nut and I would suggest refitting the crank pulley as well as the woodruff key was being pushed in when I was trying it. The pulley will have to come back off if you refit it.
7) Slacken off the tensioner bolt. The spring will tension the belt to the required level. Re-tighten the bolt to the specified torque settings.
8) Once you're happy the belt is fitted and timed correctly, start putting everything back together by reversing the steps above. Remember to refer back to my auxillary belt guide for correct refitting of the auxillary belts.

Remember...
- Thoroughly clean the old seal off the cam cover before fitting the new one. Don't overtighten the bolts, it'll leak.
- Torque required bolts to the correct settings. See above.

Now, get yourself a cuppa or a beer, you've earned it!

If there are any errors or details missing, please feel free to comment.
 

·
Any colour, as long as its black.
Joined
·
1,641 Posts
Excellent write up there fella, I'm sure it will prove extremely useful to many!

Would it not be easier to spin the engine with a breaker bar on the crank pulley? Rather than having to move the car?
 

·
Oh, hai!
Joined
·
5,001 Posts
Excellent write up there fella, I'm sure it will prove extremely useful to many! Would it not be easier to spin the engine with a breaker bar on the crank pulley? Rather than having to move the car?
Cheers. You can spin the engine with a breaker bar on the crank pulley, although I noticed that when doing up the crank pulley bolt it was pushing in the woodruff key. I didn't want to push it in too far so opted to pull the car in gear. I suppose in hindsight you could just refit the crank pulley then take it off to check that the woodruff still lines up with the marking on the case. Personal preference really. The Mk1 is fairly easy to push/pull on a flat surface. Not sure about the portly Mk2s though.


I've made some updates anyway. Reading back through it when I'm not tired I spotted some minor errors and bits I'd missed.
 

·
Super Moderator
Joined
·
10,116 Posts
if you take the auxillary pulley off first (4 m6 bolts) you can buy or make a tool to hold the crank so not stressing the gearbox for loosening/tightening of the crank bolt and also correctly reset the torque on retightening

tom
 
1 - 6 of 6 Posts
Status
Not open for further replies.
Top