Replacing BMW 520i engine with 523i

Laurcan

I was just wondering whether anyone knows whether I could replace my 520i engine with a 523i one? The engine is wrecked so I need to replace it. It's a 2000 E39 engine and the replacement one is from a 1996 e39. My other question is whether (presuming i can replace it) do I need to replace the ECU too? Sorry; I'm totally clueless when it comes to engines.

Captain Slow IRL

Short answer, no - it would be more trouble than it's worth.
The older engine is totally different (M52) to the engine in your car (M52TU) - try ebay, traynors, donedeal or specialist sites like bmw-driver.net for someone breaking a 520 with a suitable engine.

Owen

It's an electrical nightmare. I know a guy who fitted a 328 engine into a 323 (e36), and even after a BMW Master Technician and him sitting down weekend after weekend it would only fire if they turned the ignition on, waited 8 seconds for one of the ECU's to give up waiting for a signal it was supposed to get from the other engine, then put another wire to 12v, and then it would start.

Seth Brundle

Which 2000 520i engine is it (2.0 or 2.2)?
The M54 2.2 electrics would doubtfully be compatible with the earlier M52 powered E39.
If the 2000 520i is an M52 the it should be ok to change but would require an ECU swap also.
You would also need to nmotify your insurance company (which may require an engineers report) and also the motor tax office.

Stevie Dakota

Replace like with like or find a new car, anything else is just looking for expensive trouble.

ShiresV2

Captain Slow IRL wrote: »

Short answer, no - it would be more trouble than it's worth.
The older engine is totally different (M52) to the engine in your car (M52TU) - try ebay, traynors, donedeal or specialist sites like bmw-driver.net for someone breaking a 520 with a suitable engine.

What he said. If the 523i engine was an M52TU like yours you could probably drop it in fairly easily. The gearboxes are the same. It'd run lean on your 520i ECU. The ECU would need remapping for the 2.5 engine. I believe that if you change the ECU then you need to start messing about with the immboliser and keys and stuff, which is why I mention remap/reflash. All very costly especially when you consider telling your insurance company..

unkel

kbannon wrote: »

Which 2000 520i engine is it (2.0 or 2.2)?
The M54 2.2 electrics would doubtfully be compatible with the earlier M52 powered E39.
If the 2000 520i is an M52 the it should be ok to change but would require an ECU swap also.

I know of a (UK import) car where the knackered (nikasil linings ruined by the cheap dirty UK petrol) M52 2l was replaced with an M52 2.8l. I don't know the details, but it was pretty straight forward from what I've heard. The car was auto BTW and I'm not sure if he physically changed the ECU or just flashed it or did nothing at all. I'll ask him next time I see him...