How to Service the Engine on a MX5 EUNOS MIATA Mk2 / NB (1998-2005). The following procedures are also very similar to those required to service earlier Mk1 / NA models (>1990).
The service kit (See: MX5 Service Preparation) arrived earlier than expected today, so I took the rest of the day to conduct the first service of my new MX5 1.8S. This is where I will uncover any nasty problems with the engine, and I am happy to report that apart from a couple of concerns (as noted below) the outcome was positive.
The plan today was to;
- Replace the Engine Oil and Filter.
- Replace the Spark Plugs and HT Leads.
- Replace the Air Filter.
- Replace the Coolant & Antifreeze.
- Clean the Air Intake Valve.
- Replace the Fuel Filter.
- Check Brake, Clutch, and Steering fluids.
Engine Oil and Filter Replacement
Warm up the engine until it reaches normal operating temperature and then switch off the engine. Allow to cool for a further 20 mins. Heating up the oil makes it flow easier when draining.
Jack up the front of the car and support on axle stands.
Place a suitable container to catch the oil under the engine drain plug. Using a 17mm spanner or socket, undo the drain plug and remove. Now remove the oil dipstick and oil filler cap.
Once the oil has stopped draining, reach in between the inlet manifold and the fuel lines (as shown below) and unscrew the oil filter, using a tool if required. My old filter was easily removed by hand.
Fit the new filter, having first smeared a little new engine oil around the rubber seal. Screw back onto the side of the engine, and do it up as tight as you can by hand.
Refit the oil drain plug, replacing the sealing washer. Refit the engine oil dipstick and then lower the car back to the ground, after removing the oil container.
Add 3.8L of the recommended engine oil and refit the oil filler cap. Restart the engine and allow to warm up. Turn off the engine and wait five mins. Now check for leaks around the drain plug and filter, followed by checking the oil level using the dipstick.
Jack up the front of the car and support on axle stands.
Place a suitable container to catch the oil under the engine drain plug. Using a 17mm spanner or socket, undo the drain plug and remove. Now remove the oil dipstick and oil filler cap.
Once the oil has stopped draining, reach in between the inlet manifold and the fuel lines (as shown below) and unscrew the oil filter, using a tool if required. My old filter was easily removed by hand.
Fit the new filter, having first smeared a little new engine oil around the rubber seal. Screw back onto the side of the engine, and do it up as tight as you can by hand.
Refit the oil drain plug, replacing the sealing washer. Refit the engine oil dipstick and then lower the car back to the ground, after removing the oil container.
Add 3.8L of the recommended engine oil and refit the oil filler cap. Restart the engine and allow to warm up. Turn off the engine and wait five mins. Now check for leaks around the drain plug and filter, followed by checking the oil level using the dipstick.
Spark Plugs and HT Lead Replacement
Replace each spark plug in turn, using a 10mm Spark Plug socket and extension bar. Use the recommended spark plugs, which should come with the gap preset to 1.1mm. When fitting new plugs, screw them down until they are seated and then turn an extra half turn. Inspect each spark plug after removal for signs of engine problems. Each plug should ideally be a sand colour at the electrodes.
When replacing HT ignition leads, note the plastic heat shield located on the shortest lead (as shown below) and transfer it to the appropriate new HT lead.
Replace each HT lead in turn, making sure both ends are fully seated onto the spark plug, and especially the ignition coil end by pressing downwards once the lead is in place.
While changing my spark plugs it was noted that the body of one spark plug was covered in engine oil. The spark plug electrode seemed a good sand colour, and so I ruled out oil making its way into the combustion chamber. The most likely cause of the oil is the rocker cover gasket allowing oil to seep into the spark plug recess. Having checked the retaining bolts for the rocker cover it was discovered that many of these bolts were a little loose. These bolts have now been tightened down and I will check the plug again after a few miles to see if this has in fact sorted out the problem, which I suspect it may well have done.
When replacing HT ignition leads, note the plastic heat shield located on the shortest lead (as shown below) and transfer it to the appropriate new HT lead.
Replace each HT lead in turn, making sure both ends are fully seated onto the spark plug, and especially the ignition coil end by pressing downwards once the lead is in place.
While changing my spark plugs it was noted that the body of one spark plug was covered in engine oil. The spark plug electrode seemed a good sand colour, and so I ruled out oil making its way into the combustion chamber. The most likely cause of the oil is the rocker cover gasket allowing oil to seep into the spark plug recess. Having checked the retaining bolts for the rocker cover it was discovered that many of these bolts were a little loose. These bolts have now been tightened down and I will check the plug again after a few miles to see if this has in fact sorted out the problem, which I suspect it may well have done.
Air Filter Replacement
The standard air filter on a MX5 is of a replaceable element cartridge type and can be changed in a matter of minutes. Undo the two clips on the left hand side of the air box (old models may have a couple of bolts that require removal) and maneuver the lid out of its right hand fixings. You can now rotate the lid to the left to reveal the air filter cartridge (as shown below).
Before fitting the new filter, remove any debris from the bottom of the air box (I had a few leaves in mine), and wipe down the interior. Now fit the new air filter and replace the lid. Fasten the clips, and replace the bolts, if you removed any.
Coolant/Antifreeze Flush and Replacement
With the engine cold, drain all the coolant from the system using the drain plug located in the bottom of the radiator, or remove the bottom radiator hose. Remove the radiator cap and expansion tank cap to prevent air locks stopping the water draining.
My system of flushing (optional but a flush is recommended) involved pouring water into the radiator while the bottom hose was removed, until it ran clear (radiator flushed). I then reattached the bottom hose and filled the system with water. Started engine and allowed to reach normal temperature, at which point I stopped the engine and carefully removed the radiator cap (using a rag over the top to depressurize the system and deflect the steam). Removed the top hose at the radiator and started the car. Once it heats up to normal temperature the thermostat will open, allowing water to pass through the radiator, and so come out of the top hose which is now pointed towards the ground. I kept adding water to the radiator until the ejected water ran clear. Finally, drain all the water from the system again using the coolant drain plug, or removing the bottom hose.
Securely reattach both hoses making sure all clips are fastened correctly. Add 3L of water (I use distilled water) and 3L of the recommended Antifreeze to the radiator. Do this slowly to allow air to bubble to the surface, and gently squeeze the upper hose to encourage air to pass back into the radiator. Replace the radiator cap and check the expansion tank levels are also correct (between the two marks) and add coolant if required. Now start the engine and allow to warm up. After normal operating temperature is reached check for signs of any leaks. Once the engine is cold, recheck the radiator and expansion tank levels and top-up if required.
Cleaning the Air Intake Valve
As this is the first service this MX5 has seen in some time, I decided to clean the fuel intake / throttle valve. These can become gummed up and interfere with smooth running and idle. I was able to remove a lot of built up gunk using this method:
Undo the clamp securing the black plastic air tube to the inlet manifold and move the pipe to one side, exposing the air intake valve.
Using a can of carb / intake cleaner, spray on, and around, the valve plate and inner body, and allow to drain. Give another brief spray and wipe down gently with a clean lint-free cloth. Now spray the valve hinges located on each side of the valve plate and operate the throttle several times by pressing down on the exposed throttle cable attached to the left hand side of the inlet manifold. With the throttle closed, another quick spray and wipe down with a clean cloth.
Reattach the air pipe and secure with the clip, ensuring a good air-tight seal.
Fuel Filter Replacement
The fuel filter on the MX5 / Eunos / Miata is located underneath the rear of the car on the passenger side. Access to the fuel filter is provided via a small plastic cover that is removed with two screws.
Due to a lack of time, and a lack of suitable axle stands, I have decided this is a job for another day. To perform this procedure safely the fuel system should be depressurized and so some research into the correct way to accomplish this is warranted before I tackle this job. Once accomplished it will be posted here.
Topping Up Brake, Clutch and Steering Fluids
All the fluids were topped up where needed. Brake and clutch fluid is located against the bulkhead / firewall, and the power steering fluid can be checked and topped up via its dipstick, located at the front right hand side of the engine. Screen wash is also located against the bulkhead on the right hand side.
Check for Leaks
After completing all the tasks above, and verifying that everything is back in place and secure, start the engine and allow to warm-up. Check for leaks, paying particular attention to all areas we have tampered with, including oil filter and drain plug locations, and radiator hoses and drain plug. Stop the engine and allow to cool. Check engine oil and coolant levels and top up where needed.
Time for a Drive!
As part of the service, injector cleaner was added to he fuel tank. This will take some time to act, however the test drive showed a noticeable increase in power, acceleration, smoothness, and a much cleaner 'burn', with less smoke from the exhaust. All in all I am happy with the outcome, but also somewhat surprised at the additional power this 1.8 Mk2 engine has over the previous 1.6 Mk1 engine. I think I am going to like this car!
Have a question or comment? Please post it below.
Have a question or comment? Please post it below.