Hi. I’m in the process of replacing my timing belt and other related items. I have got the four bolt out that hold the pulley to the crank however I can’t get the pulley off. I have now tried to release the larger central 21mm bolt. The car is in 5th gear and I have a cam lock key between the two toothed cams pulleys.
When I try to release the 21mm bolt, using a lot of force, I am rewarded with a loud clunk and the crank pullys and timing plate move.
So the equation is, is this expected and what I want? Is the 21mm bolt loosening and the clunk is just it grinding against its socket or am I possibly buggering something else up that I’m ultimately going to regret.
I don’t think you have read the instructions on this job sufficiently well as to be honest, making what appear to be basic errors. Not meaning to sound patronising, just pointing out what appears to be the case here in order to advise you.
The crank pulley will not separate on your car so I advise refitting the four small bolts and hopefully no damage done. You need to free up that 21mm bolt which will require a breaker bar at least 2 feet long. From memory car needs to be in 5th gear with an assistant stamping hard on the brake. If you are doing this right nothing will move apart from the bolt. If anything else is moving you are doing something wrong.
Thanks Rhino.
However I have done a lot of research on this, and there is a lot if chatter about it.
On the 99 MK2 1.8 those four bolts are what hold the pulley to the crank.
This is not my only resource but pictured here. https://did-it-myself.com/miata-motor-timing-belt-water-pump-seals/
Yes, the 4 10mm bolts do hold the aux belt pulley to the crank pulley boss but chances are the aux bet pulley will be rusted to the boss making removal of it in situ almost impossible. You need to remove the 21mm bolt in order to remove the pulley boss and enable removal of the timing belt. The timing plate and aux pulley are on a small dowel pin so they shouldn’t move independently of the pulley boss. Have you seen the guide in the Downloads section?
Thanks Robbie, I didn’t find the guide in the downloads; I have now. Even with the brakes on, car in 4/5 gear and the cams locked I am still getting this clunk when attempting to loosen the 21mm. If I try to re-attach the four screws they are finding the thread. This suggests to me that the crank is turning. Any more thoughts on that, what am I damaging if that is the case?
Rhino, thanks for the input, I do appreciate it, but I am not sure I am following you. I do not see how those four screws in anyway ‘lock’ the crank. You can attach a tool to the crank with those bolts to secure the crank but without the tool I don’t see how they serve any purpose in removing the 21mm bolt. As above I am trying the car in gear and brakes on approach. Perhaps I need to bolt a tool to the crank to lock it, but that is going to be hard with the aux pulleys still attached.
Crankshaft locking tool I am thinking of is held in place by the four small bolts. Those bolts also hold the auxiliary pulley to the crank pulley.
I thought you had tried to undo the main bolt with the four smaller removed so the crank pulley could have rotated within the auxiliary pulley.
Unfortunately without being beside you I cannot see where the movement has occured but it definitely seems it has. Ideally the crank is solid and the mian bolt loosens.
Look up ‘MX5 crank locking tool’ and you will see what I mean - perhaps an idea at this stage to borrow one of these?
Not sure if you are a member or not as cannot see whilst typing but the club does lend out tools to members and I believe they may have one of these.
Thanks. I am a member. So far all the crank locking tools I have seen will require that the aux pulleys are removed before they can be attached to the crank.
As I can’t get the aux pulleys off this puts me in a bit of a bind.
I am thinking now that the clank I heard (which came close from the crank not gearbox side) may have been the belt slipping on the crank?
The car is in gear and the cams are locked with a toothed tool. I can’t think of what else there is that could ‘slip’ and make this noise.
I think I need to find a way to lock the crank, the way that the crank locking tools work, whilst still allowing for the fact that the aux pulleys are still attached.
If I could get the aux pulleys off I would be happy but I don’t think I can try to ‘wedge’ them off without damaging the timing plate.
Just a random thought. You say you have the ‘cam locking’ tool in place. I would not put this in at this point in the proceedings. Is there some excess ‘strain’ on it which is making the noise? Once the bolt is lose I would pop it in then.
You need to get the idea of separating the pulleys out of your head as in my opinion this is not the way to go.
Perhaps others would care to comment as I have only done this job three times before and until today the write ups of the job all advise removing long nose crank pulleys MK1 - MK2.5 as one unit.
One of the ways to stop the engine rotating is to drop a length of rope through the spark plug hole so that when the crank is rotated it can go over centre. You need to ensure what ever piston you chose is on the compression stroke so that the vales are closed or you will bend them and only do it if you are confident you understand what you are doing.
Not done it on an MX5, but in the distant past I had problems with an extremely tight crank pulley bolt (Triumph Spitfire, I recall). I think it had been fitted with Loctite at some time and it was so tight using the transmission didn’t work because the clutch slipped - honestly. In the end we removed the starter and locked the flywheel ring gear teeth against the bell housing with a large screwdriver blade.
Thanks all. I’ll arrange to borrow the cam lock tool from the OC. Clearly the right way to go. My desire to separate was only so I could use a locking tool. If this can be used with the aux pulleys attached so much the better.
I had exactly the same problem with my 1970 Mk3 Spitfire. I gave up on the job but I still have the timing cover gasket and crankshaft oil seal that I had intended to replace.
I’ve just realised that was in 1979!
At least that car made me learn how to replace UJ couplings (one was failed when I bought the car in 1977 and they used to fail quite regularly).
If I’m reading this correctly you are trying to unlock the crankshaft bolt by locking the cams. The crank bolt can be incredibly hard to free off and you need to use the correct crank lock tool or as mentioned put the car in 5th gear, brakes on hard with a helpful assistant, and then undo it accepting there will be a fait bit of backlash through the drivetrain. Trying to do it by locking the cams means you are using the toothed belt to lock the crank which I don’t think will work - there will be a massive amount of backlash and the clunk you are hearing and movement of the crank pulley is almost certainly the timing belt jumping on the toothed crank pulley. I’d take the cam locks off and try the gear and brake method.
Hi Merlindriver. Thanks for your input. You are correct, initially I tried by locking the cams and as you stated I believe that the belt slipped. I then put it in gear as you describe, hard on the brakes, and still I could not get it to budge. I now have some rust penetrating oil on order and have borrowed the crank locking tool from the OC. This should all arrive this week so hopefully I’ll get some success at the weekend.
:-). I have a good solid six sided socket and a reasonable bar…hopefully I will be able to find a friendly mobile mechanic in my area who will help me for a few pints if the bar is not man enough.