Mk2.5 engine progress

The crank pulley bolt was the target of today. I borrowed an electric impact gun from a fellow Westfield owner and set to work. This one apparently turns out a maximum of 450nm (331 lb/ft) and as the bolt should have been torqued to 116-122lb/ft (apologies for mixing my units) it shouldn’t have presented a problem. Of course, you knew where this was going and the bolt did indeed stay put. Lots of orange dust, but not movement on the bolt. I gave it a soaking in penetrating fluid and got to work again but still with no joy. I sprayed on some more fluid then whilst it was doing it’s thing consulted the internet to see if it was a left handed thread or something. I was sure I’d have remembered if it was, but it just didn’t make sense why the bolt still wasn’t moving.

After confirming that there was nothing unusual about the thread, I gave it another go. Still no movement… Even extended goes of 30 seconds or so only produced a ringing in my ears. I was just about to give up when I noticed at the end of the go there may have been slight movement in the bolt. It could also just have been the crank turning a little bit (though I had locked it off), but gave it another attempt just in case. Nothing for the first few seconds, then it started to move again and off it came. Phew! With the bolt removed I could also dispatch the crank drive belt pulley, crank cambelt pulley and the lower cambelt cover.

Crank pulley bolt removed

I was quite surprised to see the oil seal wasn’t leaking. I should probably replace it anyway, of course.

Next up I tackled a spare bracket that I wouldn’t need – I think it’s the air con pump bracket.

Air con pump bracket

This only had one bolt left holding it on… which wasn’t particularly easy to get to.


It was hidden behind this bit sticking out here, but unfortunately you couldn’t get an open ended spanner on it either because of the rest of the bracket.

Air con bracket bolt

I had a look in the manual to see how it was removed but the car they used didn’t have air con. It looked like the bit covering it was pressed into the bracket and could possibly have been drifted back out. Unfortunately due to the front of the bracket I couldn’t get a punch straight on there so couldn’t use too much force.

Then I noticed that as that was the only bolt left, the whole bracket could pivot on it. It wasn’t particularly professional, but I just tapped the front of the bracket with a hammer until it had rotated enough to get a spanner on it. Whilst I was doing this, the bolt lost whatever friction was holding it in so rotating the bracket back and forth soon became enough to undo the bolt by hand. Not particularly elegant, but surprisingly effective!

Air con bracket removed

Last to come out was the waterpump. It wasn’t leaking but I remember how much of a pain it was changing it on the original MX5 – much easier to do with the engine out of the car. Only 4 bolts holding that bad boy on.

Water pump removed

Not that pretty in there – looks like someone may have used plain water at some point. Coupled with that and the headgasket failure I’ll be sure to give it all a good flushing anyway.

So I now need to reconsider my plans for this engine. Originally, I just wanted to bolt the top half of the mk2 engine onto the bottom half of the mk2.5, and it was supposed to be a relatively cheap project. However, whilst I’m here it would make sense to rebuild the engine to ensure longetivity in the long run. And whilst you’re at it, what parts could be upgraded… then balance all that against the fact that MX5 engines are pretty cheap so there’s a strong argument for sticking with the original plan. If something goes wrong it’s not going to be that difficult to build again. I suspect I’ll just carry on with gasket replacement, but part of me thinks it would be nice to get the block decked to increase the compression ratio a bit… whilst I’m here…

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1 Response to Mk2.5 engine progress

  1. Whilst you’re there 🙂 …

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