Auto To Manual

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There are many people who have far more mechanical knowledge then I do. However, a few people stated a rough guide on what to do when converting from auto to manual (typically an M40-M42 swap) would be useful, so I have documented my attempt. It may not be best practice, I might have some glaring omissions, but I thought for anyone else who is trying to get all the facts together before jumping in this may be useful. My experience of engine swapping is not that great and probably worthless but forewarned is forearmed. Lets hope someone else tackling this will at least glance at this first and avoid some of the pitfalls I fell into.

1. Depressurise fuel system by removing fuse no 11 and then starting the car. Wait for it to die then remove filler cap. Remove the bonnet.

2. Remove all ancillaries from old engine (airbox leads etc).

3. Drain fluids oil, gearbox, radiator.

4. Remove all hoses, ie radiator hoses, fuel hoses, PAS hoses from steering rack ensuring you have something to catch the ATF in. Remove wiring loom also.

5. Unbolt and remove exhaust pipes from the exhaust manifold and along length of body, unless its shot, then get mr angle grinder out.

6. Remove heat shielding or splash guard which runs length of transmission tunnel.

7. Unbolt Propshaft at the differential and gearbox end and centre bearing. If you don't plan re-using or selling on, removal can be made easier by splitting it in the middle by separating the splines.

8. Unbolt the gearbox from the crossmember but not the crossmember from the body of the car.

9. From the inside of the car remove all the trim surrounding the gear lever selector. The gear knob should remove from underneath with an allen key, then move it into neutral. Underneath the car you need disconnect the selector lever, then back in the top, unscrew the metal plate with selector rod sticking through then lift this clear.

10. If reusing the radiator remove it anyway along with the shroud to prevent damage and increase working space.

11. Undo the bolts that go through the mounting arms into the rubber mounts and undo the the dampeners as well.

12. Undo the gearbox crossmember also and lift then engine clear.

13. With the engine out remove drivers side lower trim panel and remove the ECU.

14. While there remove the pedal box. This is a bloody fiddly job not helped by the fact your working in a footwell. Be careful when removing the brass rod connecting the brake pedal to the brake servo. Make sure you remove it at the pedal end, but not at the end behind the glovebox or you will have the biggest of jobs to reattach it. This is quite difficult to achieve as the threads on this brass rod run in opposite directions so as you loosen it at the pedal end, it loosens at the servo end and vice versa. If possible try to spin the pedal box once removed from the bulkhead rather than the other way round. It may seem like doing it the wrong way round, but trust me, you will save yourself work in the long run. I fell into this mistake and reattached it, it was with the help of a 2nd person. Not a job to be tackled alone because you cant see what your doing so avoid having to do it.

15. Look at the firewall and you will see an area which is already marked out for the clutch master to go through. This is an especially thin piece of metal which should just pop out. Using something like an old breaker bar or summat and apply some gentle persuasion with a hammer, this will pop the punch out and this is where the master cylinder goes through.

16. Refit the manual pedal box, reattaching the brass rod to the brake pedal. Do not bother raising the brake pedal too high at this moment as you will want to see where the accelerator and the clutch pedal will sit and raise it to about the same height. Bolt the clutch master cylinder to the clutch pedal at the same time.

You may choose to change the differential, as with, in particular the M40 auto diff being 4.45 it leaves the IS engine with an incredibly short 1st and 2nd gear as well as giving 60mph at 3000rpm. I did not do this on mine at the time as thought I would see what it is like, so have not tackled this yet. Diff changing should be able to be located elsewhere on the zone.

17. Replace the rubber engine mounts. I used E34 M50 solid rubber mounts as I did not have the money for new IS ones (approx £100). I may look to change these as time goes by. Either way, IS ones or otherwise. Replace them. Do not attempt to use the M40 ones.

18. Strap up your donor engine/box and lift into place. Line up the mount arms with the rubber mounts, lower into place but do not take the weight off the hoist without first supporting the box. A trolley jack would be ideal for this.

19. Using the manual box crossmember, bolt it loosely to the car, slide it into place, then gently lower the box onto the cross member. Make sure the higher side of the crossmember is on the nearside of the car or this will happen.


20. Under the car, in the transmission tunnel.


On the extreme right of that shot is 2 holes, and 2 prongs next to it. These are where the manual link arm support goes. You might as well buy a new one as the are inexpensive and Cotswolds BMW can get hold of them easily for you. Bolt the support in place having first slotted it over the end of the link arm. 21. If you have already, remove the old M40 loom from the bay and pull it out where it goes through the bulkhead. Feed the M42 loom through. Make sure your M42 ECU comes with a cage to mount it as mine did not. It is currently held in place with gaffer tape. Mount up your ecu and begin to reassemble the loom in the footwell. Reassemble the loom in the engine bay. It fits up more or less the same as the M40 one.

22. Next up are your fuel hoses. There are 3. One should be tucked away inside the bulkhead and is the breather hose. The next two are intake and return. Real OEM is not THAT helpful here, and shows that the top one is intake and bottom is return. However my engine was the reverse as I found out when it would not start and ended up with petrol in my mouth from the pressure built up meeting the FPR from the wrong direction.


It is worth noting that the M40 filter is different to M42 filter on all but the latest M40 engined cars. While this may not cause an issue, I am not 100% sure so for the sake of a couple of quid for a new fuel filter you might as well put the right one on. Standard M40 fuel filter is about coke can size and shape (short and dumpy), M42 filter is red bull can size (taller and slimmer) The one from your filter is intake and runs to the Fuel Rail. The return runs from your Fuel Pressure Regulator. If you are struggling, as I did to work out which is which as that is how you work it out.

23. The clutch fluid reservoir can be bolted somewhere to the battery tray (if you have one left, a common E30 fault), and there should be 2 lines from this. The first goes down to the clutch master and the second which is a solid line routes across the bulkhead of the engine bay (there should be white plastic guide clips already in situ) to the offside of the car, down underneath to where the clutch slave is. Fit this to the slave cylinder, fill the system then bleed it from the bleed nipple on the slave.

24. Next thing to do is refit the radiator and hoses. Make sure you don't forget to attach the hoses to the heater matrix as I did, losing 17 quids worth of antifreeze in the process. Refill radiator with a mix of about 60% water to 40% anti freeze is recommended. While you are there, refill and bleed the braking system as well.

25. Get back under the car, fit the manual prop at both ends (automatic one is longer and therefore cant be used) and in the centre at the centre bearing).

26. Check all bolts are torqued up as specified or at least as tight as possible, ie gearbox crossmember and engine mount bolts and any others you can think of.

27. While the car is engineless if you are handy with a welder or know a welder, weld in the bracket for the individual coilpacks. Rather then shift paint however, I have merely held the coil pack in place with zip ties and am planning on doing a coil on plug conversion. There is information around the zone about this.

28. Hook up HT leads to coilpack and plugs. Make sure you get the order right or it will run like a pig or not at all.

29. Reconnect the battery negative cable. Refit fuse 11. Hold breath, turn key. Hope it works. Enjoy.

Either way, just to pad out this post and slow everyone's bandwidth I will post up pictures from my swap.

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