Whilst Mazdas range of vehicles are normally extraordinary the CX7 seems to be the only exception to this . Unfortunately the CX7 is not much chop with the most common mechanical fault being the failure of the turn chargers on the 2.3 petrol engines. There are two factors here to consider why does this happen and how much fun is the task of replacing it.
The reason for the turbo failure is nearly always lack of lubrication to the bearing inside the turbo. This its caused by a combination of several faults compounding. This first in my humble option is Mazda own stupid fault. Advising that customers only carry out oil changes every 12,000kms is an idea on par with that of taking a canoe across the bass strait. Long service intervals allow engines to build up carbon deposits and in some cases even sludge up. This is a problem for several internal engine components in any engine but the key issue for the CX7 is the diameter of the oil supply line to the turbo, once the engine starts to carbon up or sludge up this reduces the amount of oil flow and pressure getting to the turbo. The end result is oil starvation to the centre bearing which in turn can cause complete failure of the turbo and in extreme cases can cause pretty little flakes of turbo to go through your engine. The long story short are is its completely avoidable if you change your engine oil more frequently.
Once this failure has occurred there are some very important steps you must take to avoid this happening again.
- Always replace the oil supply pipe for the turbo charger. Replacing the turbo and using the same oil supply line will only starve it of oil again and cause the exact same fault to occur.
- It is advised to remove the sump and clean it out when doing this repair. If the turbo has failed its more than likely because of the carbon and sludge build up previously mentioned. It is advised to remove the sump and clean out all the build up to avoid any risk of it dislodging and finding its way into the narrow pipe that is the oil supply pipe.
- Avoid Hot stops. This means after longer trips of rives where the engine has worked at a higher than normal Rpm. allow the car to idle for several minutes before turning it off. Done simply turn the car off after driving up steep hills or racing to work because your running late.
Problem two. How much fun is this job to do. The short answer is its not even close to fun. It would be more pleasurable to have a mid winter swim in the Volga River in speedos than it would be to carry out this job. It is located on the back of the motor and requires the intercooler removal and most of the components fitted to the passenger side of the engine to come off. If you own four wheel drive model the job is even worse as you have very limited access to the turbo supply lines from underneath. The long and the short ion this is I do not feel the is the sort of job for an enthusiast to get involved in. Unless you are an experienced mechanic I would not advise avoiding doing this job yourself.
Cost of repair. There are a few variables when pricing this job up. Removing and cleaning the sump adds several hours of labour to the job (even more in a four wheel drive model) Other factors affecting the price also include the quality of the replacement turbo, oil supply line and the gaskets used. Using GCG turbos the parts alone come in at $2400. Cheaper eBay specials can bring this price down as low as $660 but if you are willing to buy a part one with the price of a non reputable product I doubt you will find a mechanic willing to fit it. Note: most mechanics won’t fit customers supplied parts, nor should they. Labour costs will also vary depending on 4Wd or 2WD and your mechanics labour. This job at best is worth eight hours labour but a workshop can easily charge up to sixteen if exhaust studs break, oxygen sensors seize or any other complications arise from heat related damage to exhaust systems (these issues are not uncommon)
Sadly this problem is completely avoidable with regular more frequent servicing but if your reading this it is probably to late.
