I started work on the 2001. When I first looked at it, I still hoped that the engine would be repairable – maybe a bad AOS. The initial inspection of the oil filter showed plenty of metal and hopes of an easy fix died. A deeper look showed a valve and most of at least one piston sitting in the sump. At that point, to me, the engine is trash other than some salvageable parts.
I decided to try out a 2.5L 1997 engine that I have had sitting outside under a tarp for a couple years. Really not a wise choice, but there it was right next to the garage, waiting to be used or scrapped. It had been in a 2000 S before, where it never ran right and just dumped coolant and ran hot when I tried to kill it on the track at Hallett. I had offered to give it away, but the logistics never worked out. I wasn't even sure it would run anymore after sitting outside for so long. Knowing that it could be a waste of time, I went ahead and swapped it in. If it failed, I could use the engine from the '99 or just do the V8 swap in this car.
There are differences between the 1997 2.5L and the 2001 2.7L engines. There are enough similarities though that the swap can be worked out. I took all of the intake, fuel, wiring, and vacuum parts from the top of the 2.7 and put them on the 2.5. The 2.7 intake runners would not bolt to the 2.5 without 'adjusting' some of the mounting holes a few millimeters from their original location. The intake ports on the 2.5 engine are significantly smaller than the 2.7, but the seals still met the machined metal.
Other differences were the coolant purge line on the 2.5 goes to the front of the engine under the AC compressor, where on all the later engines, it connects to the top of the oil cooler. The oil cooler has a different mounting base on the 1997 engine and will need an adapter to use a later unit. I had to swap a coolant temp sensor on the front of the engine to fit the harness. Otherwise, the wires, hoses, nuts and bolts all seem to have worked out.
I started to replace the oil cooler, but found that it wasn't going to work without an adapter plate and put the old cooler back on with new o-rings. I still want to replace it. Now I'm curious: will a Tiptronic transmission oil cooler fit? Looking at diagrams of the 'Nissens' brand at Rock Auto, it looks like a good fit. Why not just get a correct 1997 oil cooler? Why not get the adapter plate and use the “S” oil cooler I bought? Sometimes I just like to make things a little more difficult for myself. ...curiosity. Anyone have an extra adapter plate or Tiptronic cooler???