In my last post, I said that I was done with adventures in the Miata for the rest of the year. It was going to be used only for occasional drives on dry days just so that it did not sit until spring without running at all. I thought I would have nothing else to say. Then I uncovered a leaking valve cover gasket, requiring replacement, so I put on my wrenching pants again and got to work.
(Interestingly, the leak was causing oil in the area of the spark plugs, which I noticed on the old plugs when I replaced them. At first, I wasn’t sure about the problem, so I posted a question on miata.net and received some very helpful answers by some very well-informed owners. They assured me that the problem was the engine running too rich, most likely due to a faulty oxygen sensor that I had already replaced. Then I thought about it a little bit more and realized that I had shown them a picture of the least oily spark plug. Looking at the other three plugs and keeping in mind the slight smell of burning oil after shutting off the car, I decided to go ahead with a gasket replacement.)
If you’re going to take off your valve cover, there’s a few other things you should probably do while you’re in there. Of course I should check the wear-and-tear on the timing belt, not that I was too worried about that since I’d already had it replaced. However, since I had to take them off anyway, I decided to replace the coil plug boots because I didn’t know I should have done that when I did the spark plug wires. Also, the PCV valve needed to be replaced since the car has passed 60,000 miles and, since it literally only cost me an extra $1.85, I decided to also replace the PCV valve grommet (more on that later). And of course, since I had to take it off, I figured might as well wash the valve cover and paint it bright red so that it looked the business when I put it back on.
So armed with my tools, my trusty shop manual, and a few helpful YouTube videos, I got to work. Like most wrenching jobs, everything started out pretty easy. I labeled the spark plug wires and ignition coils and then took lots of pictures from all angles so that I could get everything back together again. The bolts holding the valve cover on came off easily, without the need for any penetrating oil. (And can we just step back for to appreciate again the brilliance of the engineers at Mazda? Just about every bolt in the valve cover is 10 mm. You can use the same socket almost the whole time. If this was my Ford Focus that I daily, each bolt would probably be a different size and one of them would require a special hex-head wrench they only sell in Canada.)
Then I hit the snag. There’s always that clamp that won’t come off or the bolt that won’t loosen. In this case, I got buggered by the fact that I have an NB2 with variable valve timing, which requires a separate oil line through the valve cover.
You see, on NA and non-VVT NB Miatas, removing the valve cover is a piece of cake: all you need to do is remove about three hoses and then take out the bolts. If you want that modest improvement in torque that you can only get on NB2 Miatas, there are 3 additional sensors and that pesky oil line that must come off before the valve cover will lift out of place. Luckily, I found this excellent post over on revlimter.net about changing the timing belt on an NB2 that describes how to disconnect that oil line. Spoiler alert: it’s a pain in the ass. There’s a 13-mm bolt hidden behind the engine with barely enough room to fit a wrench and even less room to turn it. Eventually I ended up removing some of the brackets that held a few of the lines to the back of the engine bay so that I could turn my wrench far enough to break it loose.
But once that was accomplished, the valve cover came right off and I took it inside to clean it.
Once cleaned, the old valve gasket kind of fell apart as I tried to take it out. Next, I took everything off of the valve cover that I could and masked everything I didn’t want to paint. Here I got to use one of my old model-building trick: stick some tissue into a hole and then wet it with a paint brush. The water make the tissue expand and fill the hole so that no paint gets inside. (Bonus: when you take out the tissues after painting, it looks like you’ve had a series of bloody noses.)
After that, I applied some primer and then some red paint that promised a crinkle finish once it cured. The directions said to let it dry for 3 days before handling unless you cure it in an oven. Since the only oven I have is the same one I use to cook my food, I opted to wait the 3 days. Paint dry, I put in the new gasket and reassembled everything.
Reassembly was mostly pretty easy. More 10-mm bolts, most of which went in without a hitch since the paint couldn’t get into the holes. But there was that PCV valve grommet… I did notice that the hole for the valve in the new one was quite a bit smaller than the old one. I’m not sure if that’s because the old one had expanded over time or if they were manufactured differently, but putting the new PCV valve through the new grommet felt like trying to push a watermelon down my sink drain. And I’ve got the bruises on the inside of my hand to prove it.
And of course then there was that other thing… The thing where the bolt snapped in half inside of the valve cover. If I ever write a memoir about my adventures with the Miata I should call it “Everything Went Fine Except for One Thing.”
So yes, even though I was using a torque wrench, one of the bolts broke right off when I was tightening it. Maybe it was cross-threaded. Or maybe it was because I was operating at the low end of the range for my torque wrench and so it was probably less accurate. Or it could have been because it was just old and had been through a lot of heat cycles. Whatever the cause, it broke and I had to take it to a local mechanic, the same one who did the timing belt and who refers to the Miata as my “midlife crisis car”).
It’s not the best paint job I’ve ever done, but it’s certainly good enough for the engine bay of my car. Sure, I probably could have prepped the surface a little better and smoothed out the red paint a bit, but I don’t think anyone will notice. I was disappointed that the words, “MAZDA” and “DOHC 16-VALVE” are recessed into the surface instead of raised like on an NA or NB1 valve cover. If they had been raised, I could have easily masked them with tape so that they would stay gray instead of getting painted red.
Either way, I think it’s a nice edition and I’m looking forward to not smelling any more burning oil. *crosses fingers*
Published December 21, 2016.