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Z3 N62 Swap Wiring, Cooling & Fueling

The cooling system on this car was pretty simple to route - the hookup points are almost all in the same location and the N62 water pump has a feed port on both sides. One side was plugged, the other had a hose ran from expansion tank to the expansion tank.


I liked the way this line sort of contoured around the shock tower.

The coolant bleeder line was made with a factory BMW part from another model, paired to a custom bent line at the expansion tank and from the engine heads.

Wiring was extremely difficult and I am not going to get too into specifics because I've had quite a few people asking me about this and there are too many differences between different chassis and engine variations and all sorts of things - it's easy to mess up, so if you are following this with the idea to do this swap yourself you need to be comfortable doing the wiring yourself. You can reach out and I will help but there is a lot to it. This is a small fraction of the amount of diagrams and pinouts I had to look at.

It's a mess.

This is what a normal starter diagram looks like on most BMW"s.

This is what the N62 starter diagram to give you some idea of what all goes into this. Most of the diagrams on the N62 are equally as complicated.

Part of the reason I did this swap is I thought it'd be easy since this Z3 used the same DME plugs as this N62. What I was not counting on was the IVM, a separate fuse/relay box the N62 uses for powering various systems. I originally anticipated having to move ~10 wires. I ended up having to move, add, remove, change or modify about 100 wires.


This is part of the wiring harness I made for the IVM and various other assemblies.

And here are just some other miscellaneous pictures of the wiring process.

I later did get it cleaned up, wires were shortened where possible and overall just organized a bit, It ended up fitting neatly in the DME box when I was done.


I did also have to add a DBW pedal, but that was trivial compared to the rest of it.

Fueling was pretty simple. This car was origianlly an M52TU so it used a supply line and return line from the engine fuel rail. The N62 only uses a supply line, so I just converted to the M54 style fuel filter which only sent a supply line to the engine. The M54 and N62 run the same fuel pressure and the stock fuel pumps support ~450hp or so, so the fuel pump is still stock.

A custom fuel line from the filter to engine was later bent and installed.


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