An often talked about subject in the NC community, especially in Autumn/Winter.
They tend to last roughly about 40k miles, that’s very, very roughly as there is no exact point where they fail, the rubber seals distort, go hard or shrink and begin to pass a bit of water when they shouldn’t and gradually get worse over time.
I think most people realise that the ‘stat is an important part of the engine, it ensures it gets up to temperature quickly and that is stays at that ideal (minimum) temp too. Don’t ever think a cool engine is a happy engine, it is certainly not – but then neither is an overheated one either. Engines are happy at around 85 to 95’c. This where the oil viscosity is at its best and economy is good due to ideal fuel burn characteristics. Engine oil contains contaminants such as moisture, fuel and other byproducts, when the oil gets hot they evaporate off and are sucked out. This is one of the reasons why cars which are only used for short journeys need their oil changing more regularly.
Deciding whether your car’s ‘stat is faulty is relatively simple, even though the temperature gauge (as previously discussed) isn’t very accurate and in warmer weather we don’t use the heater so it often only gets diagnosed in Autumn and Winter.
Using an OBD reader which measures the real temperature will help, but also take a look at your gauge before you start the engine for the first time that day, the needle should move from there within 3 (Summer) to 5 (Winter) minutes of driving it. When the engine has been running for at least 10 mins the heater should be blowing warm, after 20 mins fully hot, if you’re driving down the motorway on a cold day with the heater on and it starts to blow a bit cooler than it was then that’s a sure sign it’s failing. Don’t perform any tests with it idling.
Changing it is fiddly, but easy enough with the correct tools. There were two types, long hose fitting (later models) and short hose fitting (early models), it doesn’t matter which you buy, they both fit as the rubber hoses move to take up the difference. We sell high quality Mahle brand for £20.
In defence of the cheap MX-5 as a base for a track car…..
I suppose this also could be about thinking you can buy and run a cheap MX5 and not spending anything on it.
Many people think it’s better to spend £6k on a £10k car, rather than £6k on a £2k car. So our two examples for this article are at two extremes – the modified £8k ’06 and the equally modified £16k 2012 car.
We hear and read “I’m not spending that on it! it’s only worth £xxx” all the time, I guess that’s one way of looking at it, here is another.
Whilst there are very good reasons to start with the best and latest example you can find, If you’re building a track car there is also a strong case to start with something cheap – as long as the rust hasn’t taken it’s toll on the external upper bodywork or gone too far underneath.
With any serious track car, you’re going to throw out so much stuff that (snobbery aside) it often doesn’t really matter what you started out with. They’re both going to need the engine, the suspension bushes, original coilovers, wheels, air-con and various other bits throwing out and replacing.
“Aha!” Says £16k man, “but my car has the later stronger engine!” It is a very good point too, lets look at that in detail. The pistons are essentially the same strength (and CR), the rods are ‘proper’ traditionally forged steel, the crank is steel as opposed to the earlier cast iron one and it has improved valve springs fitted which will cope better at high rpm. Ultimately it is the better engine up to a point. Did anyone ever say ‘Hey I broke my cast iron NC crank?’ No, they never did, also as cast iron is less dense than forged steel it’s actually 1.4 kg lighter too. That is a big saving in a place like that.
The valve springs and rods were also a worthwhile mod and we sell the springs for a few quid, if you’re putting big high lift cams in you’ll need different extra higher lift springs anyhow. If you’re ditching the engine for a bigger one, none of this matters.
There are a few reasons why the later models got a forged crank:
1. The main and the most interesting one is that an engine with a steel crank is slightly smoother and quieter – it has less NVH (Noise, vibration & harshness). Whether noticeable or not to your average driver I don’t know, but it is there and engine designers do site it as a reason.
2. Every new model has to be better than the last to get people to buy it. Selling cars is about making money, end of story. If Mazda bought in a job lot of different spec engine parts which added £200 to the cost of the car, they could charge the customer another £2k for them.
3. As the model got older, racing series were springing up to accommodate the NC, racers want racer parts…..
As discussed previously if there is rust showing on the upper bodywork then just walk away. The favourite starting spot underneath is the rear of the cill where it meets the wheel arch and this is easily remedied. If you buy a late model (previously stored outside) NC then you’ll still have to do some kind of remedial work underneath to prevent it getting worse as it’ll have surface rust all over it.
So we take our two equally modified cars to the trackday or even a road trip; the £8k ’06 and the £16k 2012. Who will be going the quickest? Well theoretically they’ll be both the same as they’ve both had the same mods done to them.
However in practice maybe the older car will be going faster, the reason for this is the £8k guy has less to lose so is pushing the limits further. His car is also lighter due to the rust, no I can’t write that. The £8k guy also has more money to spend on further modifications so a couple of grand more and he’ll be going even quicker, still for less money. He’ll also have a warm glow all over and be sniggering like Muttley as he keeps up with, or beats £16k guy with his £8k car.
If you do have an accident which is repairable then NC1 parts are much cheaper and plentiful than NC2 and 3. These later models are only ever scrapped if they’ve been in an accident meaning lots of damaged panels, early cars are sold off cheap or broken up due to engine failures or corrosion.
It’s not all about where you start, it’s more about where you end up. All our track and test cars are based on the cheapest, but solid cars I can find. As long as i’m fast and safe I don’t care what the snobs say, as long as I can snigger like Muttley when i’m overtaking you 🙂