_DSC5424On the weekend before last I started getting the Miata on the road to better health with multiple coolant flushes. The system was quite dirty, so the first step was draining the radiator. Simple enough, it’s just removing a plastic plug from the center of the radiator. What could go wrong?

The great thing about the first generation Miata is that it’s a simple machine. Made before the current “let’s cover everything in plastic” phase of automotive engineering, for the most part everything is right there for you to see.



That doesn’t look good…

After seeing the first flush, some friends of mine were rightfully concerned that there might be oil in there. Oil could mean trouble, because that would likely mean that the head gasket was blown, but it was going to take some more cleaning and a compression test to really get to the bottom of that. For now, I wasn’t going to worry about that. My plan was to just focus on one thing at a time. My main attention was on getting that cooling system clean, getting as much rust out of it as possible.


Gatorade bottles make great drain bottles. The only downside was that I had to fill every pitcher in the house with the Gatorade.

Things got a bit trickier from there, when after the second flush, I realized that the radiator drain plug was stuck in the bottom of the radiator, and in the process of trying to free it, I stripped it’s plastic head. Fantastic! Getting it out didn’t cost me much time. It was as simple as drilling through the plug and then pulling it out with an extractor. Unfortunately, after that a simple one or two day job turned into a week long search for a radiator drain plug.


The unfortunately stripped drain plug.

I bought one at NAPA first, since they had one in stock, then found that to be 2mm smaller in diameter than what had come out of the radiator (M10x1.25 versus M12x1.25). Later on I stopped in at their Mazda dealer to see if maybe they could pull up the specs of the factory plug (to see whose was wrong, mine or NAPA’s), but no luck, just part numbers and nothing in stock. They offered to order me one if I didn’t find it back at NAPA. I went back to NAPA and exchanged the plug I had bought for one of the right diameter and of slightly different design (it didn’t fit the countersunk area of the radiator) to see if I could get that to work. It ended up not sealing quite right.


Eventually I wised up and put some gloves on.

Over that first weekend, I found another Mazda dealership closer to my house, so I stopped by there to see if they’d order a plug for me. They would, however only if I paid for it in advance and if I did, it would be non-returnable. If this were $2-$5 I probably would have done that without a second thought, but the plug was something like $13 and a little more if I wanted to order an earlier plug that would have come in a 1.6 liter Miata (in case for whatever reason the previous owner had changed the original with an earlier radiator). So, I just went home, discouraged and feeling a bit defeated.


Dremel-ed new drain plug with the o-ring from the previous one. Notice the slight taper just at the bottom of the butterfly handle.

A few days later, I got my father in-law’s Dremel and ground the second plug that I had gotten from NAPA, into the right dimensions to fit down into the groove of the radiator. I threw away the new rubber grommet that came with it and just used the previous one, since I didn’t really have a way to precisely cut a rubber grommet. There was nothing really wrong with the old one anyway. Blown head gasket or not, the bottom of the radiator was now sealed, so I considered that a small victory. Since this entire job had taken almost two weeks, I decided to quit while I was ahead. With the head gasket now questionable, I would forego the new thermostat and radiator cap for now to just fill it back up with new water and coolant to get it back on the ground and to a shop to have the compression checked. No sense in dirtying new parts.

Despite all of the trouble, it sure cleans up nice.

And that’s roughly where I’m at now. After two weeks of being on the jack stands in my garage, it’s back on the ground. This weekend, I gave it it’s first wash since I bought it three weeks ago and it looks great. The dirty old steelies now look a little less dirty and old, and I may be painting them very soon just as an inexpensive way of sprucing the car up until I can afford some proper wheels. I have not made it to a shop yet, but I’m thinking I may have VSR do it. We’ll see how high the estimate is. I figure that if I try to do it, it may go okay, but then again if there is piston ring damage, I don’t know the first thing about honing cylinders, lapping valves, or installing new rings. If I can afford it, it may be worth it to have pros do the work so that I won’t have to worry about it further down the line. For now, I leave you with the pleasant sight of my now-clean car finally resting back on planet Earth.



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