NB Miata timing belt change

Car maintenance as art

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.

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

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

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

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 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

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

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

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.

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!

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  • Bryan says:

    Adam,

    This is EXACTLY what I was looking for before I do The Tick’s TB next year. Thanks!

  • revlimiter says:

    Glad to help, Bryan!

  • Sarah says:

    YOU took the time to polish the cam cover? You did the easy part with power tools. I donated elbow grease to that thing.

  • Sarah says:

    (Also thank you for doing the timing belt! You’re the bestest.)

  • This is an extremely high-quality guide, I am impressed. And I’m sure her elbow grease didn’t hurt 😉

  • guy that needs help says:

    You mention the VVT bolt on the back of the NB valve cover but you never mention what torque spec is should be set to. ??? Help anyone? For future reference at least I’m sure someone down the road would read this and be enlightened. Thanks.

    • revlimiter says:

      Hmmm… I honestly don’t know. Banjo bolts don’t require a ton of torque. I used a 3/8″ ratchet and just tightened it till it was “tight”.

      I’m not sure a torque wrench COULD fit back there anyway.

  • 1stTimerMiataGuy says:

    Great info – very helpful. Other sites did not reveal the cam gear alignment as well as you. Since its a non interference motor I’m not going to worry so much about moving the cams around, particularly with your description. Wouldn’t mind knowing any tricks about removing the lower crank timing gear as mine is stuck on pretty good & I want to change the crank seal & fix a loose crank pulley. Same timing gear as you pictured (I have a 91 1/2 and the crank pulley sheared off ’cause the guy before me didn’t torque it down right). Cant get a puller on it….

  • Chris Evans says:

    Did you use a OEM timing belt? I saw a Gates racing belt is this worth the additional cost or just stick with a OEM one?

    Thanks

  • Richard says:

    I used the information on your site to help with changing the timing belt, idlers and water pump on my 99 Miata excellent information and the site is well done. I also used the Miata factory manual to guide me through. This was a first for me with a dual cam engine.
    So I thought I’d share a problem I ran into to maybe save some one time and money. I changed out everything, by following instructions , but car would not start and sounded like it was out of time. I took it apart and rechecked everything with the same results. After a day of contemplation and research, I took the front of the engine a part for a third time looking for what was wrong rechecked everything again. I re-assembled the engine with the same results, researched the internet again for more clues to no avail. Bewildered, I had the car towed to a garage to have them look at it. The mechanic got it running the next day.
    One hundred and sixty eight dollars later, I found out the problem was the crankshaft position sensor plate. I had installed it backwards not knowing it had anything to do with the crank position sensor simply because since I could not find it because, the crank sensor was covered with heavy grease from the leaking cam seal, nowhere in the manual does it give the location, and the blow up page from the manual labels the crank position plate as just plate, which could have given me a clue. I had assumed since I had not come across it and had no idea it was in the area it was not an issue.
    One more thing, I noticed oil spots on the garage floor, the valve cover gasket was leaking along the rear in front of the coil packs. You could see the oil on the edge of the head where it was not sealing. I removed the valve cover and used some hi-temp silicone along the back between the gasket and the head. I have not seen any leak as of now. It would not hurt to seal it when putting it back together.
    So anyway everything is working fine and the car runs better than before. Hope this helps someone.

    • revlimiter says:

      Ouch. heh.

      Yeah, the little plate behind the crank damper is directional. Miatas have worn these little plates since 1996. I got one backwards once years ago. Took me a little head scratching to figure out. Ever since, I’ve placed those parts (crank pulley, sensor plate, crank damper) in a very careful pile.

      Thanks for the comment! I’m sure it’ll help someone.

  • Nic Smith says:

    WOW!!! this has been the most helpful link I have come across in the 8 collective hours of internet searching I have spent on this problem trying my dambdest not to pay someone to set my timing after my rebuild (which I did myself minus block boring and crank balancing to properly weighted pistons and rods) first time rebuilding a motor and I was not going to let the timing push me into a mechanics shop THANK YOU!!! the picture on the cam position setting IS ACE!! PROPS MY NEWLY FOUND UNCONFIRMED FRIEND.
    Why cant this be the first link that BING claims they will produce minus all the BS you dont want or need?!
    once again THANKS 1,000,000!

  • Mike Jones says:

    Thanks again for the writeup and excellent pictures. I’ve got the factory manual for my car (2004 Mazdaspeed Miata) and the Fanatics guide…neither of which go into much detail about tensioning and aligning the belt, so your picture of the two cam pulleys was invaluable.

    Thanks again!

    Mike

  • julie says:

    when does a timing belt need to be changed? I have a 2000 with 117,000 miles. what do mechanics charge?

    • Adam says:

      Timing belts are 60,000 mile items. Except in California where they’re 100,000 mile items. So, you’re coming up on a change.

      No idea what you might be charged. I’ve not visited a mechanic for this sort of work in 15 years.

  • John says:

    When you said you used an NB timing belt kit, where did you purchase this kit? I was looking at the FM kit but I doubt they use OEM equipment.

    On my previous cars I went 60k on the belts and 120k on the pumps. Is this fine for the miata’s as well? I don’t mind a bit of labor but I am cheap.

    FYI this for for a 2002 non turbo. Thanks for all your help!

  • Devan says:

    Hi,
    I was wondering if you could help me. I wanted to know what size the 3 Torx screws are that are used to secure the cover plate on the VVT cam.
    Thanks,
    D

  • art says:

    Can someone tell me how the round plate plate that goes in front of the boss pulley on the crankshaft has little dimple that triggers a signal. its not flat and is either closer to the engine or farther because it has an offset.

  • art says:

    finished time belt replacement. used ebay kit, the left cam seal came from mazda because the ebay kit is not for VVT. everything else fit just fine.
    replaced thermostat and hoses.
    the crankshaft bolt required an impact wrench to take off

  • Buck Mickell says:

    Most of what you assert is supprisingly precise and it makes me wonder the reason why I had not looked at this with this light before. This article truly did switch the light on for me as far as this specific topic goes. However there is actually 1 factor I am not necessarily too comfortable with and while I attempt to reconcile that with the central theme of your point, permit me see just what the rest of your subscribers have to point out.Nicely done.

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