M40 to M20 swap - couple of questions

[IainB]

Bit of background on this one, recently purchased a 318 Touring as a stop gap car (previous car ran out of MOT and TAX, and rather then get an MOT....bought this one ) anyway - it had an idle issue which gave a brilliant kangaro effect when sitting at lights / junctions etc etc (its an auto btw....this gets better and better!!). Finally tracked down the issue to a leaking inlet gasket, after getting 'annoyed' at the idle control valve - then find it now smokes like buggery...... yes another top buy

Thats the history out the way - I had decided to pull the engine and re-build but now Ive seen the cost of a top end kit + bearings + everything else, im thinking it will be easier to get another complete donor and swap engines straight across, so, to get to the reasoning behind my first post over here, what will I need? Im thinking of only going to the 2.0 as I have another car for my 'speed issues' so, I would guess at, engine, ECU, engine wiring loom?

Is it a case of engine bay loom to car loom, or will I need the complete loom from the donnor car, will I have to change radiators etc and have I missed anything else? Are there any issues swapping from auto to manual as well, or indeed will the M20 bolt to the autobox that sat behind the M40?

Thanks for any assistance - hope to spend a lot more time over here - something else to modify
Iain

edit - just been out having a further play with what im now affectionatley calling 'the smaller money pit' and my idea on the loom looks like Ive confused myself - is this a complete engine only loom? in which case is this as easy as old engine, loom & ECU out - new in?

Couple of further questions as this is the tourer - do I need to do anything suspension, brake wise?

[Andyboy]

You need;

Engine and gearbox and possibly a prop too. The Tourings have got 6 cylinder front struts and the diff will be okay with a 2 olitre. The engine look plugs into the C101 (round) connector on the bulkhead and goes through the bulkhead to connect to the ECU. The radiator is no good - you'll need a 320i/325i radiator. It is possible to use the 318i M40 rad by extending the pipe that goes to the remote M20 heaqder tank down to the M40 rad but you can have terrible problems with air locks. You'll also need to change the coding chip in the rev counter and swap the power steering pump pipes. Basically - forget it. Just go and buy an decent old M40, they are still about for peanuts (but avoid the E36 one).

[IainB]

Thanks,
Had done a bit more searching and it doesnt look as easy as first thought (well relatively speaking anyway!), thanks for confirming it though, appreciated

[jmc330i]

The swap is easy, especially if you get a complete donor car - you will have everything needed.

I did my M40 to M20 swap in a couple days from jacking the car up, to driving it up the road (minus the bonnet) to see how the 2.5 went

The M20 engine loom plugs into the C101 (round plug) and the ECU plug goes through the bulkhead (which can be a bit tricky).
The only bits the 318i doesnt have are the mounts for the header tank on the passenger side inner wing and the AFM mounts are slightly in the wrong place. If you can swap the engine, box etc, those little bits are no worries.

[IainB]

Started this today after picking up a complete donor car (320SE with all the goodies), managed to strip the engine bay and gearbox, though only after forgetting 1 of the manifold bolts, lifting the engine half out... realising, going back underneath (you know whats coming now, dont you) undid it then watched the auto box make a graceful arc down onto my chest - leaving a nice gearbox imprint bruise, ooooh havent had this much fun in ages
Tomorrow will be the continuation of ripping the loom out, then starting on the donor, wish I had spent the money on something half decent now!!

[Brianmoooore]

There's an easy way of doing things and a hard way.
Engine and gearbox come out together, and the engine wiring loom should remain attached to the relevant matching engine.
Although the touring will have all the right suspension bits, you should probably swap the front springs for the 320 ones, because of the considerably heavier weight of the six pot.

[jmc330i]

Exactly what I did Brian.

And yes, definitely fit the 6pot front springs - I know from experience!

[IainB]

Cheers Guys,
Havent stripped either loom out the car yet, but from what I can see it all looks interjoined with the normal loom? Am I missing something (I hate electrics, give me a BBC on carbs with MSD anyday!! )
Will swap the springs over also - Thanks (well until I can afford new struts and lowered springs!!)

[jmc330i]

The engine loom unplugs at the C101 (big round plug) by the fusebox - thats where the engine loom joins to the car loom. The only bit that goes into the car is for the ECU - pull the ECU plug back through the bulkhead into the engine bay and the engine and loom comes out as one.

The fusebox etc stays in the car.

[Brianmoooore]

Engine loom is completely seperate from the body looms. Only connections are the C101 plug and socket, and 12V+ and earth at the front battery position. As JMC330i says, the engine loom goes into the cabin, but only because that's where the ECU lives in the dry and warm.

[IainB]

Dammit - just came in to edit my post, but too late now
All sorted, I had followed an incorrect lead to the fuesebox....shouldnt have admitted that should I!!
Loom, ECU all out now - at least im making the mistakes on the wrong engine
Thanks for your help guys, appreciated
Iain

[jmc330i]

Good point. It doesnt matter how the M40 comes out, as long as the M20 comes out all in one it will be easy to put back in the other car.