NB Miata timing belt change

Car maintenance as art. Click for a larger version.

I’m an NA Miata owner. For those not hip to the language, that’s the first generation of the cars. We have NA, NB, and NC so far. Anyway, I’m an NA Miata owner. I love pop up headlights. I love the simplicity. I love everything about them. They really appeal to me and I’ll likely always own one. I’ve done nearly everything you can with an NA Miata, maintenance-wise. I don’t need manuals anymore, except for torque specs. I’m one with the NA.

So when it came time to change the timing belt on Sarah’s new-fangled NB Miata, I started to research the differences and how to do it. See, there’s this wacky cam timing thing over the intake cam. A lot of searching on miata.net forums didn’t turn up a single how-to in easy language on changing a timing belt on an NB2. I *did* find a dozen little separate snippets of info and tried to piece them together. So here you go, an NB2-specific timing belt change.

The before shot.

You might notice the engine bay is a little yucky. Poor Bucky doesn’t get quite the obsessive treatment that Sharka does. But we’ll have a cleaner engine bay in just a few paragraphs…

Before you start, you’ll need an NB timing belt kit. Mine came with one smaller cam seals and one larger cam seal. The larger one goes on the intake cam. I also got a front crank seal, a timing belt, an NB2 valve cover gasket, and a timing belt tension spring. I also ordered the alternator and a/c accessory belts and a water pump kit that came with the pump and two gaskets.

Things that did NOT come with my kit that I didn’t need but was worried about: The little copper washers for the oil line on the back of the valve cover (pictured later) and any extra gaskets for the timing control system. Don’t worry about this stuff! You’re fine reusing parts.

I also did a fuel filter change. This way-annoying job did NOT get photographed, but here’s a few tips. Order two spare quick-connect clips. They’re Mazda part number T032-42-694 and don’t come with the replacement fuel filter (BP4W-13-4809U). Apply those to your new fuel filter before starting the job and you’ll not lose much fuel at all. If you have to switch the clips from the old filter to the new, you get a stream of fuel piddling out for how ever long it takes. But back to the timing belt change.

NB coil-over-plug spark packs

The first thing to take off is the cam cover. To do that, you have to remove the coil packs. They’re kinda difficult to mix up, but I labeled them anyway. Also remove the associated wires and small acorn bolts from around the cam cover.

Variable timing control oil supply

This is the only difference between the NA/NB and the NB2 cam cover removal. You have this bolt in the back with a 19mm head to remove and two copper washers on either side. It’s easy to drop one when you remove the bolt. Try not to.

Bolt in hand

There’s no need to remove any of the other timing control stuff from atop the intake cam. Just this one bolt. You *will* lose some oil when this comes off, so be prepared with a couple paper towels.

The 2-wrench timing belt trick

The intake cam has three Torx head screws of the T-25 size. Once you remove those, you have access to the 17mm bolt head holding that cam pulley on there. I fortunately had the correct size torx socket.

From here, you can follow the standard NA timing belt change instructions and have no problems. I’ll add a few tips that make life a little nicer. Above, we have the 2-wrench trick. Before taking off your old timing belt, put a wrench on each cam (there’s a spot on each that’s meant for this) and figure out a way to keep those wrenches together. I like my big C-clamp. Make sure to have your timing marks aligned and your crank at Top Dead Center before doing this, or it’s kind of pointless.

The FM Big Snout

Here’s another tool that makes life nice, the FM Big Snout. It sure beats trying to hammer the crank seal in with a cardboard tube or large bolt. You just pop this bad boy on there and screw down the center crank bolt until it bottoms out. Ta-da! Seal installed. Also, dropping the swaybar really helps.

Water Pumpless

Every time I change a Miata water pump, I always forget exactly how much stuff you have to remove, so I shot a photo this time. You can remove basically everything. Power steering? Yes. Outlet neck? Yes. It’s not so bad, but it is annoying when you think everything’s out and there’s still *one* more part to unbolt.

Timing belt alignment – you can click on all of these pix for larger versions, but this one really benefits from the larger view.

It’s really hard to take a shot of good timing belt alignment. If you’re too high, the marks on the back plate look unaligned. If you’re too low, you can’t see the 19 teeth between the two marks on the top of the cam pulleys (note that the NB intake cam has no upper mark and barely any bottom mark). You shouldn’t have too much slack in the belt between the cams. If you have some, grab that intake cam with your big wrench and rotate it backwards just a bit to eat up the slack and then tighten the idler pulley below the intake cam. Spin the crank around twice and re-check belt alignment and tension.

Shiny.

While the cam cover was off, I took the time to polish it up a bit with a poly brush. It’s not exactly “polished” but it does look very clean and purposeful now. The rest of the engine bay got a good cleaning as well.

Don’t forget to burp your radiators!