Buyers guide or new owners? A few things you should know about the NC.

This is a bit of a (sometimes) tongue-in-cheek article about people who don’t do research and when online forums and FB pages become boring and repetitive, don’t take that too seriously, everyone has their place in the community and new people are coming on board all the time. Do take the facts seriously though, they are very real. It isn’t a ‘How to’ guide, there are plenty of those already out there if you take time to look, but most people can’t be arsed, it’s just easier to post up and bore the pants off everyone else with repetitive mundane questions, but never mind, this guide is here to save you 🙂

So you’re searching for or you’ve already you’ve got your newly purchased NC, you didn’t do any research so it’s likely to be rusting away merrily underneath and the engine is due to run out of oil due to the pistons rings being gummed up. Here are the things which everyone in the community knows and is fed up with talking about, but you don’t….

Rust.

Car manufacturers are far from stupid, yet some people think they are. On the one hand they need to keep selling new cars, on the other they do not want to see their old ones driving around with visible rust all over them. So what do they do? Up to a certain time don’t allow them to rust on top whilst letting them rot away unseen underneath. Take note of that, it’s important yet very few take any notice of the consequences and buy simply by what they see on top.

It’s an old MX5, 2006 cars are 10 a penny, 13 yrs old at the time of writing and will have rust – somewhere. They were never wax injected at the factory and the underseal was patchy. In my experience mileage tends not to matter where corrosion is concerned, it’s the age of the car and how or where it’s been used. It often starts at the base of the inner rear wheel arch where it meets the cill, this is visible from the outside, even more so when you get behind the cill with the car lifted up or by using your (phone) camera with flash to see it. Often it just looks a bit rusty, but hit it with a screwdriver and sometimes it’ll go straight through. On the positive side it’s quite easily repairable and shouldn’t cost too much either. The later the car, the less chance of it going too far. If you intend on stopping it you need to act now.

The bit you don’t normally see, but really you should.
These were for anchoring down the cars when shipped., They have no underseal around them, were often not capped off, rust like buggery and let water into the cill cavities.

Under the bootlid often looks like this, unsightly, but in the grand scheme of things not a big problem.

Rear wheel arch lips rust eventually because the arch liners hold dirt and soil against them in big clumps. What happens is these clods of earth or road debris get soaked with water (often salt water) and retain it like a sponge. Hours or days later they are still wet and holding it against the metalwork of the car. Solution? Get down and dirty, clean them out. Initially run your gloved fingers carefully around the inner lip and see how much is still there and push it out. Often it’s enough to grow some potatoes in, then get a hosepipe and point it outwards from inside the arch and wash them clean.

Rear subframes rust, not usually to the point of perforation, but sometimes on really bad ones. There are two brace bars which bolt on to the floor pan and subframe to stabilise it, they can rot away completely on top.

Not as bad as it looks as they’re still doing the job and easily repaired or replaced.
Out with the old, in with the new.

They tend not to rust much at the front, the subframe will a little, but like the rear one, it’s made from thick steel and the engine heat dries it out, wheel arches and around the wing indicator and (aluminium) bonnet sometimes corrode, but it’s rarer. Also where the glass divider in the door meets the doorskin is very common on earlier cars – easily treatable in the grand scheme of things. If the rear wheel arches are bubbling then it’s quite advanced and bad news, a proper repair job there will be a lot of money, mainly because paintwork is needed, in some cases it can be much of what the car is worth. We’ll talk about corrosion in more detail in another blog later.

Electrical

This electrical plug (bottom left) in the fusebox has brown grease around it, it’s supposed to look like that, don’t worry about it.

Engine Oil

The actual grade isn’t as important as you might think, but for general road use a 5/30 or 5/40 fully synthetic will do. If your oil changes coincide with Winter and Summer you can use a slightly thinner (0/30, 0/40) in Winter and thicker in Summer, just open a manual and take a look for heavens sake. If you do a lot of track work or have a boosted car then 5/50 will do a better job. Mazda were more interested in economy than anything else, both with MPG and oil changes, this leads us onto:

Engine.

‘Just because it say OXO on the side of a bus doesn’t mean the sell them there’ I was told as an apprentice.

The engine is a Duratec AKA MZR, it was designed by Mazda, not Ford, it isn’t a Ford engine, they just happened to be in partnership at the time so Ford used it in their cars too. If you want to upset a Ford Fanboi who has one tell him he’s got a Jap engine under the bonnet, when he says it isn’t ask him why it’s got a Mazda bellhousing pattern and no Ford ‘boxes fit it…..

It’s generally a very well designed and strong unit, it’s only when humans intervene (or don’t when they should!) that it can break and given you’ve probably bought a second hand old motor there is little you can do, apart from choose wisely and just hope, although if it’s smoking run a mile or expect an engine rebuild.

Read here about a very specific engine problem you need to know about: http://www.duratecnc.co.uk/?p=146

There is a second reason for rod bearing failure and it’s less well known. If the ECU has had a bad aftermarket map put in it then something called ‘Detonation’ will occur in the combustion chamber, this is more prevalent with forced induction and engines which are burning oil. These are uncontrolled explosions in the combustion chamber which send shock waves through the pistons and rods. It squeezes the oil out of the rod bearings (top and bottom) so they come into contact with the crank damages them.

An engine burning oil will not be a healthy one. Your engine is designed to run on petrol and air, not oil! When oil is introduced the combustion chambers and exhaust ports will coke up, the engine will run into detonation territory as per above. The factory ECU will detect this and pull the timing meaning it will be down on power, if it can’t stop the detonation by doing that or everytime it does it before the engine detects it the bearings will take a hammering – and that’s before it completely runs out of oil.

So after digesting all of that what do you think the value of a car with ‘Full service history’ or even ‘Full dealer service history’? Well i’m sat here looking at the records of a car in the workshop, it has full dealer service history and had it’s oil changed with semi synthetic every 12,000 miles or so. I’m rebuilding the engine because the rings are stuck together and it ran out of oil….

My carpets are wet.

‘Oh God not wet carpets again’, is the usual retort when the subject comes up for the third time that day. It’s an MX5, it will leak at some time or another, the cures are very simple though and widely documented online. The first one is a drip from behind or under the dashboard: Externally beneath the plastic scuttle cover at the base of the windscreen are two square plastic grommets for screws to go into (one on each side), pull out the stupid dried up foam washer, clean it out carefully then put some silicone sealant around and under them, job done. The other main leak is from the drains behind the seats outside the car at waist level being blocked, shove something down to clear it after reading or watching an online guide on how to do it and the pitfalls of internal flaps and so on. Currently I’m investigating a theory that when the drains block it can overflow into the boot so bare that in mind. Trying to dry out a piss wet through car in the middle of Winter is going to be very difficult, particularly as the water is now under the carpet, has soaked the underlay and is sat against the floor pan. Prevention is better than cure, DO NOT think it won’t happen to your car, it will, they all leak at the front.

My gearbox is difficult to use when cold

If you pushed me out of bed, outside the door and told me to run to work i’d be pretty cranky too, maybe I was a gearbox in a previous life, I need to be treated carefully and introduced to the World slowly on a morning with copious amounts of coffee and reading about wet carpets again. The answer is simple, just slow down your changes, feel it through and wait for it to warm up, don’t put coffee in it though. If it still persists when hot and you have other issues then take it to a specialist, in these instances changing the oil usually does very little as there is something fundamentally wrong with it. We have our own special blend of oils here which do combat some issues (clunky, crunchy and synchromesh issues), it isn’t for resale sadly as its a trade secret and is only put in here at the workshop, sorry.

If you have a six speed then the gearchange collar/bush at the base of the gear lever never fitted properly from the factory. Take note of that fact, it is not worn, it was just never manufactured very precisely. Put the car in gear, wobble gear lever left to right, a bit too much play for your liking? MX5 Parts supply a brass replacement, I can attest that theirs is obscenely accurate, I can’t speak about any others. It sits in what is known as the ‘gearbox turret’, this is a reservoir which contains its own oil separate to the main gearbox.

I put lowering springs on and the car hasn’t gone fully down.

The suspension arm bushes on the front upper arm have not been slackened off to reset them to the new ride height and are twisted, holding the car up. To some (lesser) degree this does happen at the rear too, especially when the bushes are seized onto the through bolts and have been twisted to set the geometry or the car lowered. The cure is simple at the front; slacken off the offending upper bolts and with the car sat on its wheels, the bushes will rotate, then tighten them up. To explain a bit more of what is happening: The inner bushes front and rear are of the torsion type, so are locked in place by the through bolts, when the arm moves up naturally and down it twists the bush which contributes to roll stiffness.

I can’t read my dipstick.

If you can’t put a metal rod into a pool of oil and read off the level you need help, but it won’t be long before electric cars will save you so don’t worry. Mazda are very clever, they will sell you an overpriced ‘Special needs’ dipstick which suffers from the same problems, or you can just learn how to use your existing dipstick, you dipstick. A handy guide here on what you may be doing wrong and how do do it right: http://www.duratecnc.co.uk/?p=165

The ‘oil pressure gauge’ does weird things.

No it doesn’t, there is just a misunderstanding about oil pressure. When oil is cold it’s thick so the gauge will read higher (and vice versa), when the engine revolutions are higher the oil pump revolves quicker so the oil pressure goes up (and again, vice versa), are you with me on this? Ah now here is where it gets interesting, the OP gauge in an NC is actually fake, it isn’t actually reading oil pressure at all, but mimics it perfectly for a normal healthy engine. What the ECU does is take a signal from the engine water temp sender and also reads engine RPM, it blends these together to make the gauge work exactly as an OP gauge should if the engine is healthy.

Whilst we’re on the topic of gauges the water temp gauge lies like a Pikey. You might wonder what the heck this is all about. All manufacturers do it, the average motorist has very little idea what is going on under the bonnet so has to be insulated from it. If people saw the temp going over 100’c when stood in traffic they would worry something was wrong and the driving experience would be spoiled. It’s possible they would take the car back to the dealer and ask ‘What is wrong with my car mofo? The gauge needle is all over the place!” The fact is an engine will see over 100’c stood in traffic and it does it no harm, once on the move it will come down to about 80 odd or so, but the gauge will still be midway. In reality engine temp is up and own and all over the place, it’s quite normal.

Whilst we’re on the topic of oil, or lack of it, the engine is fitted with a low oil warning pressure switch and i’m not sure why yet! I’m sat in a car which is clearly knocking very loudly and there are no warning lights on the dash board. I wonder if the warning light comes on when you’re sat on the hard shoulder and your pistons are back on the motorway somewhere.

If you do require a proper working oil pressure gauge then check out the store, we do sell kits.

A lot of peoples relationships with cars is psychosomatic, when they’ve spent money on pointless braces, Delrin door blocks, new dipsticks, ‘performance’ air filters, loud exhaust, changed the oils etc then naturally they get a feel-good-factor, the car is of course now handling much better, the gearbox is smoother and it’s much more powerful. The aftermarket sellers know this, the car manufacturers know this. Another ‘trick’ Mazda use on their later NCs is piping engine noise into the cabin, seriously they do. If you look under the bonnet of these models you’ll see a pipe and valve arrangement taking ‘induction roar’ from the engine inlet to somewhere under the dashboard. As you can imagine being a miserable git, on my road car it’s blocked off.

It will have a fancy marketing name, but the large pipe at the bottom there is simply carrying engine noise into the car.

The clutch biting point is too low or early

On some cars it certainly is, it’s not uncommon to have the clutch biting when the pedal has barely left the carpet, these cars are terrible to drive and you’ll wonder (like me) how it got so far on in its life without anyone doing anything about it! There is a fix however and its simple. If you look under the dash up at the pedal box you’ll see the clutch pedal has a nut and bolt pushrod adjuster on the back of it, loosen the lock nut and turn it clockwise until the biting point is better. Please note DO NOT go too far and have the biting point halfway up the pedal stroke, you only need a little bit extra. When you’re done you have to get hold of the clutch lever sticking out of the side of the gearbox box and make sure it’s loose and still has some forward and backwards movement, if not the release bearing can run against the clutch diaphragm all the time which will wear it out prematurely and could cause clutch slip problems..

The battery goes flat

The batteries are small to keep the weight down, also the battery could be past its best. With the obvious out of the way, then yes these cars do have a battery drain issue fitted as standard. The earlier cars seem to be better in this respect and will last roughly a month, whilst the newer ones closer to two weeks if left unused for that length of time. There are various remedies for this, but if you take disconnect the battery it will cause a couple of very minor issues when it’s reconnected: The engine warning light may come on (turn it on and off again usually clears it), the idle speed will be a little erratic for a short while (it’ll sort itself out) and the traction control light will illuminate too. This latter one will go out when the steering is used fully from lock to lock and the ignition turned off and on again. None of these are anything to worry about and quite normal. Radios are rarely coded, but if they are hopefully someone wrote the code in the handbook or paperwork somewhere…..

Sticking brake calipers

Very common on daily driven cars. Either front or rear especially during or just after Winter. If you don’t notice it pulling to one side a bit, one of the discs not as clean as the others then maybe you will when it overheats, you feel a vibration on the motorway or when it finally fails its MOT. Sometimes the sliders have seized, sometimes the pistons themselves.

16 Replies to “Buyers guide or new owners? A few things you should know about the NC.”

  1. Great article. Thankyou. I have an early NC 1.8 soft top. I must be very lucky as I don’t seem to have any of the issues mentioned. Maybe yet to come. Hope not. Current mileage by the way 79000.Look after car as best I can and try to emulate exactly what you say. One comment I would like to say is I change engine oil and filter twice yearly even with average mileage of 2500. This to keep timing gears and chain clean an well lubricated. No dreaded cam belt to worry about!!! Cheers.

    1. I’m sure you are right. Once a year more then adequate but I was in the motor industry for 45 or more years so tend to over do things to be over sure!!!

    2. Thank you. That’s some great info!

      I’ve got a 1.8 with around 130k miles. My oil consumption is around a quart per 1000 miles and hasn’t changed for the past 10k miles since I got the car. There’s no leak nor smoke. Should I be worried, and is there anything I can do about that?

  2. great article, have a 2011 Kendo, looks incredibly clean and tidy, I’ll be getting gt in the air for a good look under!

  3. Hi I live in Birkenshaw I’m looking for advice etc as my nc has a few of the issues you mention
    Are you a business please could you forward you’re details so I could come & see you many thanks John

    1. We can fix your car, but don’t really want to just discuss it as time is money. There is a contact form on the website.

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