1994 Mazda MX-5 Miata Long Term Road Test - Maintenance

1994 Mazda MX-5 Miata Long-Term Road Test

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1994 Mazda MX-5 Miata: Thermostat Walkaround

September 07, 2010

tstat old new.jpg

This won't be nearly as cool as one of Dan's Suspension Walkarounds, but what the heck. I had both of Project Miata's thermostats (the old and the new one) in hand during my cooling system festival and saw some notable differences.

Maybe you'll learn something from this. Perhaps not. In any case, here goes.

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1994 Mazda MX-5 Miata: The Bonehead Rule

September 06, 2010


Recall a while back Project Miata's cooling fan was operating erratically. It's now fixed (I'm pretty sure).

The short explanation: replacing the coolant thermosensor at the back of the head did the trick, as expected.

For those curious / bored readers, the resolution entailed some other cooling system shenanigans as well. Okay, the whole process sort of turned into a goat rodeo. Click on to read the long and twisted saga.

After replacing the relay, my next plan of action was to replace the thermosensor. I should have kept my eye on the ball and just done that. Instead, I got distracted.

A friend had a fancypants aluminum race radiator left over from a customer's Miata project car. It was removed simply because the customer is one of those bigger-is-better guys that always wants the latest thing. Whatever, he didn't need it and gave it to me. Used for only a short time, the radiator was in surprisingly good shape, plus was made by a reputable big-name manufacturer and not some chintzy Chinese off brand.

Perfect, I thought. We'll be adding power, so some extra thermal capacity is a must. I threw it in Project Miata and even sealed it up nice with a bunch of foam strips so that all incoming air goes through the radiator (and fans) rather than around it.

The next day while commuting to the office, the temp gauge started to climb.

Now, if you're familiar with factory temp gauges, you know that they are essentially worthless. They're highly nonlinear, meaning they sit in one happy place over an absurdly wide temperature range. This is because most automotive consumers suck -- when they see a temp gauge move around, they freak out.

In response, manufacturers have over the years "deadened" their temp gauges so that their needles hardly budge even as coolant temp varies widely. This comforts the lowest common denominator customer into thinking that everything is just peachy but makes for a less-than-useful gauge. This, of course, sort of defeats the purpose of the gauge.

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1994 Mazda MX-5 Miata: Drinking Problem

September 03, 2010

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One quart every 1000 miles. That's the rate of Project Miata's oil consumption.

Judging by the extra glossy block, accessories, splashpan, subframe and steering rack, some of it leaks out the cam seals. The rest is being burned off in the catalytic converter.

This engine is not long for this world.

Jason Kavanagh, Engineering Editor @ a lot of miles.

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1994 Mazda MX-5 Miata: Erratic Fan

August 02, 2010

1994 miata fan relay.jpg

The other week I noticed that Project Miata's radiator fan was cycling on and off erratically. Opened the hood. I put a finger on the fan relay. It was clicking over indecisively as if possessed -- so the fan was doing what it was being told, but it was being told wrong.

There isn't much to the cooling circuit. The ECU commands the fan relay based on advice from a coolant thermosensor.

Of those three components, the relay is the most likely to crap out. I theorized that the sporadic clicking is the relay in its death throes, and that soon it wouldn't function at all. If/when that happens then the fan won't run and engine go boom.

Short of time and feeling frisky, I ordered a new relay and popped it into the fuse box this morning. At five bucks, the stakes were low. Went for a quick spin and... no difference. Time to find my multimeter.

Jason Kavanagh, Engineering Editor @ 178,xxx miles.

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1994 Mazda Miata: Bringing Balance To The Force

July 07, 2010


In last week's post about driving our Mazda Miata on the highway, I mentioned that I thought a tire was out of balance because of a vibration coming through the steering wheel. We had the new tires balanced when we had them mounted, but apparently Miatas are very sensitive to even slightly imbalanced tires. So editor Jay Kavanagh (who's overseeing the Miata project) suggested getting a "road force" balance. A few commenters on that post also suggested the same thing.

So I tracked down a shop (my local Tire Pros) with a road force balancer by using this site. As the description reads for the Hunter GSP9700: "[It] solves wheel vibration and tire pull problems that other balancers and aligners can't fix."

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1994 Mazda MX-5 Miata: Vital Fluid

June 30, 2010

miata oil add.jpg

Just checked the old Miata's oil and it was down a quart. So it seems to be using/losing a quart every 1,400 miles or so. Granted, it's got nearly 180k on the clock so I'm sure it's burning a little (though we see no smoke out the tailpipe) and Jay Kav told me it has a nasty front cam seal leak. Of course, this malady will be taken care of as we continue to improve this scrappy little go kart.

John DiPietro, Automotive Editor at 177,800 miles.

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1994 Mazda Miata: Suspension Walkaround

June 25, 2010


A lot of car people really admire the original Mazda Miata because it's such a simple and well-executed design. But there are also those who'll never get it. I heard one myself last week while I was driving our '94 Miata with the top down: "Look at that. That car is so bleeping blay."

Whatever, dude. I call I can say is you're missing out. He probably assumes it's front-wheel drive, too.

Let's move along. I'll point out Jay's bolt-on mods along the way.

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1994 Mazda Miata: T35 Torx, Round Two

June 24, 2010


I know how much you like my pink striped beach towel as a backdrop for Mazda Miata component photographs, so I'm pressing it into service once more. I like it so much that it's in my rag bag, the place I go when I need to sop up spilled motor oil.

The above bolt is one of four that holds a pair of convertible top clips to the top of the Miata's windshield header. But this one is not from our 1994 Miata project car. No, it's a spare I had lying around in my garage.

Why does this matter? Our '94 has worn header clips. The grooves that the convertible top latches fit into are worn, and that means the top is hard to latch down properly. In fact, it recently came loose at speed.

So I figured I'd swap the worn latches out for my pair of "barely used" spares. But the bolts in question take a T35 Torx bit and I can't get them loose. T30 is too small, and T40 won't fit. I have no idea how I removed this one 19 years ago, but its mates are thoroughly stripped out so it must have been sketchy.

If this sounds familiar, it is. Our Ford Flex's front brake rotors need a T35 Torx bit (Ford swears we're wrong, but my ill-fitting T30 and non-fitting T40 bits say otherwise). The Flex rotor replacement wasn't critical, so I hadn't yet bought this inexplicably hard-to-find tool while I waited for a hole in my schedule.

Eazypower.com has tons of T35 Torx bits listed on-line, but their security certificate has expired and my browser throws up huge warnings. Sorry guys, but I'm not going there.

So I ordered one from someone else on Ebay. I'll fix the Miata and the Flex as soon as the stars align and I receive this much-needed tool. Stay tuned.

Dan Edmunds, Director of Vehicle Testing @ 177,361 miles

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1994 Mazda Miata: Refused

June 22, 2010


Our 1994 Mazda Miata started going mildly haywire a few days ago. All of the gauges went kaput, save for the cable-driven speedometer. The turn signals ceased signaling. Michael Jordan resorted to using the trip odometer to decide when to add fuel over the weekend.

This morning I crawled down by the pedals to have a look at the interior fuse box--the one that's located on the kick panel in the neighborhood of the hood release lever and the driver's left foot.

But the cover and it's all important fuse diagram were missing, so I referred instead to the one on my own personal 1991 Miata, currently in a state of partial disassembly in my garage.

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1994 Mazda MX-5 Miata: DIY Floppy Mirror Fix

June 04, 2010


Project cars aren't just about mods and going fast and having fun. Sometimes you're simply dealing with the idiosyncracies of an old car.

Since the day we picked up Project Miata, its driver's mirror has been loose. Not flopping around, but enough play to where it shakes annoyingly at speed. The screws at the mirror "base" were tight as can be, though, necessitating a deeper look into the situation which didn't happen straight away. The issue was minor enough that we just lived with it. Until now.

Over the weekend I decided to fix it. Pretty simple, really. Unbolted the mirror. Saw that between the base and the door is a rubber gasket. Aha, there's the culprit. That gasket was old and flattened, giving the mirror leeway to wobble.

I just trimmed up a piece of 1/8"-thick sticky-back foam pipe wrap I found collecting dust in my garage, stuck it to the gasket -- being careful not to block the little cutout that allows water drainage -- and reassembled. Voila! Rock solid now.

Next up in Rattle Patrol -- something is loose behind the dash on the passenger side, and it rattles obnoxiously... sometimes. Can't locate it even after removing the glovebox and poking around under there. Drives me crazy.

Jason Kavanagh, Engineering Editor @ 176,532 miles.

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1994 Mazda MX-5 Miata: Preventative Maintenance

June 01, 2010

1994 mazda mx-5 miata beatdown tie rod end.jpg

Not unexpectedly, Project Miata has some worn-out underpinnings. Old cars are like that.

It could be argued that this oozing tie rod end is still serviceable -- hey, there's no real play in the joint, and the grease is... well, there's still grease left. But we'll use this image as a good excuse to swap 'em out with new tie rod ends from the LE / R-package cars. Slightly longer (and a whole lot fresher) than the stock Miata tie rod ends, these will reduce bump steer somewhat on our lowered car and lower the blood pressure of our Risk Management department staff.

Other preventative maintenance we'll tackle at the same time: upper control arms and new wheel bearings.

What's up with the control arms? During the suspension overhaul, I noticed that one of this car's front upper balljoints has about 1/16" of axial play. And you can hear it rattling when you drive it over rough pavement. Since Miatas have their upper front balljoint integrated into the control arm, they're not serviced separately -- you simply buy new control arms when the balljoints go bad. On the plus side, the new control arms also come with fresh bushings.

A sticky-tired Miata that's driven hard (particularly on a track) will go through wheel bearings faster than do many other cars. As such Spec Miata guys are fastidious about their replacement even though they repack their bearings with high-temp synthetic grease.

Our bearings are very likely original and if so have 176,000 miles on them. They're not roaring, but Miata wheel bearings can be totally shot and not make noise. Also, determining a bearing's health using the ol' grab-and-shake-the-tire technique doesn't always work on a Miata for some reason. What you do get just before the bearings are ready to completely self-destruct is crummy turn-in and accelerated tire wear. So, while we're in there...

Jason Kavanagh, Engineering Editor at 176,429 miles.

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1994 Mazda MX-5 Miata: Under The Knife

May 03, 2010

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What's that? Shut the heck up and start spinning some wrenches on Project Miata? Right, then.

Here, our longterm Miata is under the knife at MD Automotive in Westminster, CA, where the owner was kind enough to let us use his lift, tools and sage advice. Lots to talk about in the coming days. In the meantime, you should be able to spot what we're up to here.

Jason Kavanagh, Engineering Editor @ 175,310 miles.

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1994 Mazda MX-5 Miata: A Good Starting Point

March 29, 2010

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You know those images you saw of Project Miata in its intro article? Well, that photo shoot was literally the first time any of us had driven our new old 1994 Mazda Miata with any kind of spirit.

And in those few hours we learned a lot about what's good about it and what needs work.

Hit the jump for those early impressions and the reason for the above image.

The Good:

First, the car has an immersive quality. Even this many years on, the first-gen Miata's inherent appeal shines through. And despite this particular car's neglected state, it's just plain fun to drive.

Its quick and linear steering responds to your inputs faithfully and without delay.

The spryness that results from its low curb weight cannot be synthesized any other way. It simply exudes fun.

It's quite easy to work on, too.

What Needs Attention:

It lacks suspension travel. Especially the rear suspension. Any kind of bump has the suspension working against the bump stops. Boing, boing. Not good for grip or ride comfort.

The lack of chassis stiffness is really noticeable too. The thing shudders over bumps as if its structure was made largely of crepe paper.

Wide open throttle throttle results in hilariously gradual progress. All noise and very little actual movement. The canyon road we were on creeps uphill ever so gently, and this was enough to keep the car's ass end chained to the pavement. It was impossible to induce any detectable oversteer at corner exits, even when getting all rowdy with it. A sports car that cannot powerslide is no bueno in my book. We'll definitely have to address that too.

What's Leaking:

Oh, and during said photo shoot, the shift action got stickier and stickier. As the lead photo suggests, afterwards we swapped in some fresh synthetic trans (and diff) juice. Yes, its underside is a murky mess.

The gearchanges still get a bit stiff with heat (esp 2nd gear), though, so chances are good that the clutch hydraulics are tired.

So, with that out of the way, what do you want to see from Project Miata?

Jason Kavanagh, Engineering Editor

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Past Long-Term Road Tests