I just wanted to share for posterity my experience replacing the Coolant Temperature Sensor on my 86 240. This car had been sitting for years when I bought it and have replaced just about every fuel and fuel injection component in the car except the ECT, which I just couldn't reach.

I finally decided that I had to replace it to cure some driveability issues, and I approached it from the top. I removed the air intake accordian hose, then the eight nuts holding the intake manifold to the head. Then I just pulled the manifold up and back enough to get a 12pt 19mm deep socket behind there. Unplugging the harness was the hardest part. Once it's unplugged, the manifold can be moved for more clearance. The sensor came out with little effort and a little coolant. As others have said, have the replacement sensor ready. Also have a replacement manifold gasket ready. I trimmed the gasket that I got from FCP to match the one I removed. I didn't have to scape any of the old gasket off of the head, but be sure both surfaces are clean.

There's no mention of torque for the manifold nuts. I tightened them in stages so it would be even across the manifold.

Double check that everything is hooked back up, in case any hoses came loose in the process.

The whole job took less than an hour.