Tracking and repairing a coolant leak

Miata nerds will know all about the water plug on the back of the cylinder head, and how difficult it allegedly is to reach. Follow this link and scroll on down to the Troubleshooting section; you'll see what I mean.

I saw that cap when I rebuilt my engine, but decided to leave it alone. Because I was lazy, and because I already had enough to do. Running to the parts store to replace something that wasn't broken when I already had enough problems to deal with, well, that was a low priority.

Once I reached Florida, however, it decided to finally break and leak. I noticed when the coolant temperature started to creep up, and water would leak from somewhere at the back of the engine when I refilled the radiator. When I discovered the source of the problem, I feared what could be a job so distasteful as to warrant spending several hundred dollars at a repair shop. I was, very thankfully, wrong.

I was able to reach the spring clamp with one of the two pliers pictured above. For the replacement, I stacked two caps from the cap assortment pictured (stacked so they were thick enough to make use of the clamp) and reinstalled the OEM spring clamp with the same pliers. A worm clamp would be nearly impossible to install. With the engine cold, it was a pretty easy job. You can see what remains of the old cap at the bottom of the picture.

Conclusion: this job is not nearly as difficult as I previously thought.