The 2018 season has Started so lets GO4IT!
MX5 City sponsor Go4itracing in the championship this year comprising of 3 drivers Martin Tolley, Jack Warry and Stephen Foden.
In case you aren’t even remotely familiar with how internal combustion engines work, you should know that cam belt (also called timing belt) is one of the most important parts that regulate engine operation. It synchronises rotations of camshaft (or camshafts) and crankshaft of an engine. Moreover, rotation of the camshafts also regulates the opening and closing of the intake and exhaust valves, whose perfect timing is essential for optimal operation of the engine. Lastly, some engines also use the cam belt to drive things like water and oil pumps
This is why the breaking of a cam belt causes havoc for the car. Whichever car you’re driving, if the cam belt breaks, you’re getting stranded where you are and believe it or not but this is the best-case scenario. For most engines a broken cam belt also leads to serious damage since pistons usually destroy the valves.
This last thing is not something that will happen to your Mazda MX5, because it’s engine is a rather non-common non-interference and its pistons won’t damage the valves even if the cam belt breaks. However, having in mind all the issues, it’s easy to see why a timely replacement of the cam belt is a great idea.
On a side note, some manufacturers use timing chain instead of the belt. This is so mainly due to the fact that they are more durable, but timing belts have their advantages as well – they are far more cost effective, lighter and quieter, all of which seem like a must for a car such as the Mazda MX5. Moreover, the only downside to the cam belt is it’s lower durability, but a timely replacement does away with this issue completely, so let’s see when you should do this and what should come with it.
This is where things get a bit confusing. Even though most parts are basically the same in different markets, replacement intervals vary greatly. Now, it is common for manufacturers to have some differences for vastly different markets, but with the MX5’s recommendations, things do get a bit weird.
For example, in some markets there is no time limit for the cam belt’s functionality, it being dependent only on the mileage. However, in Canada, for example, the MX5 service manual states that you should replace it after every five years (60 months), provided you haven’t replaced it in the meantime due to high mileage. This is the most conservative time regulation, most others stating six years’ replacement schedule.
Speaking of the mileage aspect, the strictest one we’ve encountered states that the replacement is necessary after 54,000 miles. Most service manuals will stretch to 60,000 miles, but there are those that will go even further.
Due to the earlier explanations stating that a broken cam belt will not cause major breakdowns of the engine on the MX5, many owners opt to test its durability, or at least stretch it. This is where we get the info that is lacking with interference engines. Namely, risking a broken cam belt on one of those is almost unheard of, since it is not worth a dead engine, but on the MX5 we have seen loads of cam belts going strong for more than 100,000 miles. Judging by experience-based reports, 80,000 miles should keep your car safe with a single cam belt, although we would not dare recommend skipping periods that the manufacturer states.
In all honesty, cam belt life mostly depends on how much you abuse your car and how hard you drive it. This is exactly what leaves the room for the stretched replacement intervals. 60,000 miles that the manufacturer most commonly states should be a safe margin for almost any MX5, regardless of the market and the level of abuse, which means that most drivers who do not torture their cars shouldn’t experience any problems even if they go a bit over the stated mileage.
I know there are owners out there who are still stuck on that won’t-do-loads-of-damage-even-if-it-breaks part, feeling that it simply means they can drive it until the cam belt breaks and then replace it. So, is that a good idea? NO, IT IS NOT! If being left stranded god knows where is not enough of a reason for you to replace the cam belt before it breaks, you should know that there are other things to consider.
First of all, a worn belt (so, a still functional one) can cause problems with timing accuracy. We have spoken of how cam belts control synchronisation of the camshafts and crankshafts and why this is essential, so a problem with timing due to a worn cam belt can hinder the operation of your engine.
Secondly, when replacing the cam belt, some other things should be replaced as well. These include things like water pump, pulleys, tensioners, loads of seals, heating and cooling hoses, accessory belts and more. Some of these are a must, some depend on the condition, but each and every one of them is essential for proper engine operation, so replacing your cam belt after a certain mileage can also prevent other malfunctions of the mentioned parts.
Lastly, there is a pretty practical side of the sliding replacement schedule. If the service time is approaching close to the winter when most MX5s are driven far less, you can opt to postpone it for a few months and thus save money and make the next replacement later.
MX5 City now have three features in the Modern Classics Magazine where Joe Vollan's talks about his experience with us restoring his Mk2.