I currently have a crankshaft pulley problem (wobble, tears up PS belt) in my MK1 MX-5. I know for sure I need to replace the pulley since it has a chunk out of it.
My 5 is a 1996 1.8 UK model.
The part number for my model is BPD3-11-401A, but a new one is expensive and I want to find a used one.
I’m unable to find any decently priced used ones, but I can find pulleys for the MK2 (1998-2002).
I am wondering if the pulleys and interchangeable and whether it is possible to put a MK2 pulley on a MK1 mx-5, and whether I would use a MK1 or MK2 pulley boss.
To be quite honest I’m unsure at the moment.
I haven’t had the car for long and don’t have the tools myself to take anything related to the pulley myself to check if the key-way is damaged.
The wobble is very subtle, my main problem is that it is throwing the power steering belt. The pulley has a chunk out of it and seems to be shredding the belt.
I bought a new belt and 2 weeks later the edge of it had been ripped and it would just slip instantly.
I think it could quite honestly be a problem with the harmonic balancer buy I’m not very knowledgeable.
Key way may be damaged ,most likely from previous timing belt change and the garage not knowing that the key itself has very minor taper on one side/end thats barely noticable unless you are familar with it.Other than that the crank bolt may not have been tightened up enough.Are you sure the actual power steering pump is aligned correctly with the crank pulley as th pump is adjustable front to back (on sliding sleeve with long bolt through it)
I am not trying to be nasty here or condescending as not everyone can know everything but!
It appears to me that you need someone with more mechanical knowledge than you appear to have to look at this problem rather than just trying stuff in case it may work.
Further to our communication and to assist others…
The outer pulley for the MK1 / Eunos 1.8 is not the same as that fitted to the MK2(1998 - 2005). The later cars have a timing trigger plate fitted behind the pulley.
The Boss is also different.
Woodruff key, bolt and timing belt pulley are the same for all cars (1990 - 2005) - the only cars that have different parts are the early short nosed crank 1.6 cars(1989 - 1990)
I have a Mk2 crankshaft pulley fitted to my Mk1 1.8 engine, with PAS. I did remove the timing trigger plate and everything fitted and aligned perfectly.
The Mk2 pulley had the harmonic balancer while the original MK1 pulley did not.
Thanks for this information, it’s very helpful to know this is possible. However, depending on whether I can find a good used one, I think I will end up getting a MK1 pulley.
If you don’t mind me asking, I have a few questions about this.
Does the harmonic balancer help the longevity or performance of the pulley at all, will using the MK2 one be beneficial?
And most importantly, what is the timing trigger plate and how can it/how easy is it to be removed?
I have seen pictures of the backs of the MK1 and MK2 pulleys, and the MK2 is flat while the MK1 isn’t.
The timing trigger plate is just a thin metal plate that is fitted to the rear (inner) edge of the pulley and is used for the Mk2 timing system. It must come off easily, but it is so long ago that I did the change, that I can’t remember how I did it. It can’t have been difficult.
The harmonic balancer is built into the Mk2 pulley. As to its advantages, you will have to ask Mazda’s designers as to why they thought the MK2 needed this (or somebody else on the forum might know the answer to that question).
The harmonic balancer helps to prevent broken crankshafts!
The first time I came across one of these was on the brand new E-Type of our (independently wealthy) Maths master, and on the front of the straight six engine there was this little extra flywheel/pulley that the manual called a Torsional Vibration Damper.
This was of great interest because another one of us sixth formers had just broken the crankshaft on his Dad’s Mk3 Zodiac (Derrington branched exhaust and triple SUs to double its power) by over-revving it. The maths master was able to work out how much extra rotational mass/inertia was needed on the front end of Zodiac’s straight six to stop the crank resonating. This was incorporated into a new fan belt pulley made in the metal-workshop. After that the Zodiac’s rev limit was because of the valve springs bouncing…
NM - There are apparently two outer pulleys on the MK2 - a cast one on some of the MK2s(1998 - 2000) and the trigger plated steel version fitted to the MK2.5 and some MK2s I believe. It sounds like you used the steel one with trigger plate. Did you use the MK2 boss, woodruff key and bolt?
Interesting read about the harmonic balancer Richard. Mazda must have had their reasons for developing this for the MK2 but I have not heard of an MX5 crankshaft breaking. We have all heard of the keyway problems with the early short nosed crank 1.6 engines(1989 - 1990). Keyway problems can also be a problem with later cars where the pulley is not replaced correctly. Other than that the only crank damage I hear of regularly is oil starve mainly on the 1.8 cars damaging the crank.
Lots of mods made to the MX5 for various reasons but not heard of anyone replacing their MK1 pulley with a MK2 version before. Always good to know what is possible and what actually works.
The good thing here is that I am sourcing a part for Harvey and there is a choice of original MK1 fitment or MK2.5 if preferred.