Tuesday, January 26, 2016

Crankshaft Endfloat

If you look back in this post here, you'll see that I had yet another failed attempt at installing the crankshaft. (Read here and here for previous failures!!). This time there were two things that I wasn't happy with; One was the fact that I'd not measured the running clearance and the other was that after measuring the crankshaft endfloat, it wasn't within specifications.

As the previous post successfully addresses the running clearance issue, this post will concentrate on that pesky endfloat problem and get it to where it should be.



The last time I installed the crankshaft, I used feeler gauges between the thrust washers and the crank to get a 'feel' (pardon the pun) of the endfloat. Although this method is what they use in the Haynes manual, everyone I talk to advises that to measure the endfloat accurately, you're best using a dial gauge.

As I have dial gauge, I did just that and low and behold, I got a different measurement than when I used the feeler gauges. Using the feelers, (which I've covered in this post here) I 'guessed' the endfloat to be in the region of 0.05mm (about 2 thou), which although at the lower end, was just within spec. However 'guessing' can be wrong as when I used the dial gauge, I barely manage to register 0.02mm (less that 1 thou) of endfloat which is too small.



I wondered if the difference was maybe down to a problem with the thrust washers themselves, so when I was at Mini Spares, I picked up a new set of standard sized thrusts in the hope it would fix the problem. Although installing them did give a little improvement as it took the endfloat up to 0.03mm, it's still below the specified minimum of 0.051mm (2 thou) of endfloat. Not the result I was hoping for!




After a little research on the subject, I read a few accounts where other people had suffered the same issue and used some fine 'wet and dry' paper on a flat surface to linish the back of the thrust washers to get the necessary running clearance. As I only needed to remove a tiny 0.01mm from each of the thrust washers, it seemed like a good idea, so I thought I would give it a try.

Measuring each of the thrust washers, they were all measuring a very consistent 2.35mm no matter where I measured them. So that gave me a target of 2.34mm to aim for.


I decided to use some 1000 grit and take it very slowly as I didn't want to over do it and end up at 2.33mm. So I found a nice flat surface and set about rubbing the back of the thrust washers on the sand paper and took them from this ..



To this...


Yeah, almost the same I admit, except a little shinier, but after rubbing and measuring and rubbing and measuring, I eventually hit my target on all four thrust washers. Result.



And as if by magic, after they were cleaned and slotted back into place, the endfloat was absolutely bang on where I would have wanted it at just over 0.05mm (2 thou)




So there you have it, a 'Have a go Hooligan' story that didn't end in disaster! In fact, it actually went quiet well, making it two successes in a row! Maybe after the recent run of bad luck, things are starting to look up. Let's hope it continues as I move on to measure the big end running clearances...



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1 comment:

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    Engine Codes: N47 D20 A, N47 D20 C, N47 D20 B, N47 D20 D, M47 D20 (204D4), B47 D20 A
    Part Number: BMWCRSN47
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