Early turbo'd cars and reliability ?
Discussion
Mine is a '90 with 230,000km and a turbo, it's been perfectly reliable bar a failed ECU. I'm not certain if the crank issue was resolved when the conversion was done, however.
The condition is more important than the mileage. If you go ahead, do a proper job and service regularly, I do an oil change every 3-4k miles and use high heat NGK plugs. 200BHP engines will be quite happy, 250+ will start pushing the limits of the engine.
Alternatively, particularly if you're going for 200+BHP, have a 1.8 engine prepared and dropped in; they're relatively cheap to pickup and have more potential for further gains.
The condition is more important than the mileage. If you go ahead, do a proper job and service regularly, I do an oil change every 3-4k miles and use high heat NGK plugs. 200BHP engines will be quite happy, 250+ will start pushing the limits of the engine.
Alternatively, particularly if you're going for 200+BHP, have a 1.8 engine prepared and dropped in; they're relatively cheap to pickup and have more potential for further gains.
AFAIK its more of an 'internet problem' than a real issue, just make sure that whoever changed/changes the cambelt knew/knows MX5s as the crank problems are most often caused by poor workmanship. I heard from one MX5 specialist that he'd seen as many failures from long nose MX5 cranks as he had short nosed cranks - I expect if it was going to let go it would have by now anyway.
Mine is a '90 with 155,000km and 255rwhp, though the engine was stripped and rebuilt with GTX rods when the turbo conversion was done.
Mine is a '90 with 155,000km and 255rwhp, though the engine was stripped and rebuilt with GTX rods when the turbo conversion was done.
Edited by GravelBen on Friday 4th February 11:58
I had the "short nose crank pulley blah blah" failure on my 90 G' Eunos.. (still bitter about it TBH as I didn't have the time/money/inclination to repair it at the time and let it go for a song..)
It does happen, but, as people have said, as long as people know what they're doing when changing belts, all should be fine..
It does happen, but, as people have said, as long as people know what they're doing when changing belts, all should be fine..
It really isn't an 'internet' problem. It happened to me just last year on my 1990 1.6 150k miler. Certainly wasn't down to servicing either. It was a design fault on the first years run of cranks. More here: http://www.miata.net/garage/crankshaft.html
I'd disagree with that. The problem is usually caused by incorrect fitting of the crank pulley and/or torquing of the crank bolt allowing a tiny bit of movement of the pulley on the crank. This movement will slowly wear the woodruff key & keyway which, if left too long is pretty terminal. If everything is fitted properly then there is no movement so no wear and no damage.
Looked into this at length as there is a ton of misinformation around which has passed from web page to web page and is often spoken as gospel.
Poor design and or dodgy servicing led to problems on earlier models.
Later redesigned models only really had problems due to sloppy servicing.
To put your mind at rest, pop the bonnet with the engine running and look at the bottom pulley.If it is wobbling about like a trainee plate spinners collection, you could be in trouble down the line.If they are wobbling, as a rule, further down the line, performance will start to slide as apposed to an instant disaster scenario (unless of course the pulley falls off)
It's also worth adding that if not too far gone, the later models can often be repaired with very few ill effects, but earlier cars become a bit of a lottery.Some repairs may last an age, some may not.
Poor design and or dodgy servicing led to problems on earlier models.
Later redesigned models only really had problems due to sloppy servicing.
To put your mind at rest, pop the bonnet with the engine running and look at the bottom pulley.If it is wobbling about like a trainee plate spinners collection, you could be in trouble down the line.If they are wobbling, as a rule, further down the line, performance will start to slide as apposed to an instant disaster scenario (unless of course the pulley falls off)
It's also worth adding that if not too far gone, the later models can often be repaired with very few ill effects, but earlier cars become a bit of a lottery.Some repairs may last an age, some may not.
Edited by Digby on Friday 4th February 18:55
I'm happy to be wrong on this one but the only ones I've seen go are where either the bolt wasn't torqued up correctly (Mk2.5) or where the incorrect woodruff key was fitted or the key wasn't fitted correctly (early Mk1). In the case of the Mk2.5 the failure was within a month of cam belt service but the Mk1s it was a long time later i.e. well over a year.
Well chaps, you can talk about dodgy servicing, new bolts, use of voodoo etc. But it is a marginal design (why do you think Mazda went to the expense of a long nose crank after a few years?)
I noticed mine had started to go a few years ago when I had my head off, I'd put my No.1 piston at TDC, and was scratching my head as to why the timing mark on the pulley was out.
It had moved and hammered out the keyway. With the help of a very good friend, who has a mill in his garage, I put on a new pulley and a stepped key we made up, using bearing fit and the 'Loctite' trick. Been fine for the 15k it's travelled since.
If it's okay now I wouldn't worry about it. I think had the car supercharged on a short nose crank I'd view it as more risky, but on a turbo there's no extra load on the crank pulley.
I think if I wanted to do some preventative maintenance I'd have the pulley off and 'Loctite/bearing fit it back on. Looking at the timing belt change, I think that could be done by just removing the three bolts that hold the pulley itself in place, not disturbing the timing belt pulley which is held on with the infamous bolt.
I noticed mine had started to go a few years ago when I had my head off, I'd put my No.1 piston at TDC, and was scratching my head as to why the timing mark on the pulley was out.
It had moved and hammered out the keyway. With the help of a very good friend, who has a mill in his garage, I put on a new pulley and a stepped key we made up, using bearing fit and the 'Loctite' trick. Been fine for the 15k it's travelled since.
If it's okay now I wouldn't worry about it. I think had the car supercharged on a short nose crank I'd view it as more risky, but on a turbo there's no extra load on the crank pulley.
I think if I wanted to do some preventative maintenance I'd have the pulley off and 'Loctite/bearing fit it back on. Looking at the timing belt change, I think that could be done by just removing the three bolts that hold the pulley itself in place, not disturbing the timing belt pulley which is held on with the infamous bolt.
Definately a real issue and there were examples of failiure at very young age before cambelts were changed so its not just a servicing issue- Older brother was service receptionist for Mazda at the time. And yes mine went last year after 105k its easy to diagnose though just look for a wobble to the pulley and count the number of slots in the front early ones had 8 slots later less susceptible were 4 IIRC . when it goes it gets worse over time until you have no power below 4k revs. The loctite fix works very well though and was designed with cooperation from Mazda US.
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