MX5 Clutch Master Cylinder Replacement
Finally a post about MX5 repairs - which was the entire point of this blog in the first place!
A complete new cylinder is about £65, but I went for a rebuild kit as I'm very tight with brass. These are about £15.
Replacing the cylinder is pretty straightforward. There are 2 nuts securing the cylinder to the bulkhead - 1 accessible in the engine bay and the other at the top of the clutch pedal (remove the panel beneath the steering column for access). The pipe connection is 10mm. I disconnected the wiring to the fuel injectors/CAS for better access, enabling me to waggle it off.
The cylinder is disassembled by removing the circlip (internal circlip pliers required), then just tapping out the innards. As long as the bore of the cylinder is unmarked, you should be able to get away with just replacing the parts in the kit:
Clean out the bore with fresh brake fluid - it needs to be spotless. Lubricate the new parts with brake fluid, attach the seal to the spring and insert it, then insert the plastic disc, then the new piston. The latter needed a light tap with a rubber-faced mallet to persuade it to fit. Install the new circlip, and it's done.
When refitting the cylinder to the car, ensure the pin at the top of the clutch pedal slots into the piston - this might be easiest by getting as assistant to hold down the pedal, so the pin protrudes through the bulkhead. Then bolt the cylinder on, reconnect the pipe connection, and refill the reservoir.
Now, the bleeding part. The bleed nipple is on the slave cylinder; I had to completely remove this to get any fluid to appear here. Once the fluid started to come out, I reinstalled the nipple and used the conventional method to complete bleeding.
- Symptoms: clutch bite point is very near the floor, or won't disengage at all; gears difficult to engage.
- Diagnosis: the clutch slave cylinder is a known weak point on the NA-NB MX5, but this is quite easy to spot as it'll leak fluid - check the bellows if there isn't a pool underneath the car. However, on my car there was no fluid loss, just a general lack of action. Replacing the fluid (which looked like black tea) helped for a day, but it was gone again the next morning. This could only mean the master cylinder had failed.
A complete new cylinder is about £65, but I went for a rebuild kit as I'm very tight with brass. These are about £15.
Replacing the cylinder is pretty straightforward. There are 2 nuts securing the cylinder to the bulkhead - 1 accessible in the engine bay and the other at the top of the clutch pedal (remove the panel beneath the steering column for access). The pipe connection is 10mm. I disconnected the wiring to the fuel injectors/CAS for better access, enabling me to waggle it off.
The cylinder is disassembled by removing the circlip (internal circlip pliers required), then just tapping out the innards. As long as the bore of the cylinder is unmarked, you should be able to get away with just replacing the parts in the kit:
When refitting the cylinder to the car, ensure the pin at the top of the clutch pedal slots into the piston - this might be easiest by getting as assistant to hold down the pedal, so the pin protrudes through the bulkhead. Then bolt the cylinder on, reconnect the pipe connection, and refill the reservoir.
Now, the bleeding part. The bleed nipple is on the slave cylinder; I had to completely remove this to get any fluid to appear here. Once the fluid started to come out, I reinstalled the nipple and used the conventional method to complete bleeding.
- Result: lovely smooth clutch action, and £50 saved to spend on chips/ice cream.
