But would it work?
The answer is no, at least not as a direct drop in. Here are the things to watch out for:
1. Upper and lower intake
The throttle body on the 03 is in the upper collector and comes from the side, the 06+ is on the lower collector and feeds from the front
2. Throttle body
The 06 one is larger and is fully electronic
3. Oil pan + oil pickup tube + dipstick
The 06 one is deeper, but holds relatively the same amount of oil. The dipstick then has to go deeper to read accurately, while the pickup tube goes deeper to suck up the oil
Along with a different side profile, the oil drain plugs are in different locations
4. Water Pump
The 03 pump also carries the solenoid that controls the hydraulic fan. I'm sure you could use the 03 in an 06 in a pinch, but I'd plug or just loop the hydraulic ports.
5. Thermostat housing
There's a single fitting that faces down on the M45 and up on the other engine. Get creative if you have to
The entire filler neck is also offset to the right to accommodate the 06 intake elbow at the front of the manifold.
6. Some water hoses on the back of the engine heads
Just check before it goes back in the car
7. Vacuum hoses around the valve covers and intake
The hoses are molded differently, so when replacing the VC gaskets just take a careful look.
8. Electrical harness
Different style ECU or ECM
The transmissions also use different harnesses. Click this link for pictures
9. Motor mounts
The 06 ones are larger and the mount-to-mount spacing is different on the subframe, so the mount brackets are different sizes too
10. Exhaust manifolds
Slight differences in the head stud patterns, but the ports will match. Move the studs around the 03 and you can use the 06 manifolds on them. Also, the mating flange between the primary and secondary catalytic converters is rotated 90 degrees
11. Starter location
Ultimately, this is the biggest wrench in the works. The 03 one is on the right side while the 06 one is on the left side. This is important because it means the 03 engine will not mate to the 06 transmission
Can you make it work physically? Yes, if you transfer the trans bellhousing between transmissions so that they mate. What I foresee, is having to do some custom wiring for the 03 engine as the starter moves closer to the 06 battery.
You could do that, but I decided to take a gamble on a JDM engine. They are an interesting combination of an 03 intake, an 06 block (hence starter location) and an 03 oil pan
I bought a 60k mile JDM engine for a little over $1,000 so it made perfect business sense to to me.
If you go the JDM route for your replacement, reuse your accessories, as they bolt into the same locations:
- Power steering pump
- A/C compressor
- Tensioners and idler pulleys and belts. These are actually exactly the same
- Starter is the same physically, but different part numbers.
- Ring gear with flex plate, and bellhousing (hence transmission) bolt right up
- All the relevant sensors and respective connectors are the same, so no need to change anything after you change the wiring harness. (except that fan solenoid on the water pump, of course)
You probably want to see pictures for proof. I have videos