300ZX Clutch Problems

Clutch Kit Parts
Clutch Kit Parts

This is the story about a clutch job that transformed into a budget busting repair. My 300ZX clutch problems began with a rear main seal leak. It wasn’t long after the clutch started slipping that the Z wouldn’t move at all. When I put the vehicle up in the air to check it out I saw what was going on.

The rear main seal wasn’t leaking very much but it was enough to cause the clutch to fail. Oil and friction material such as the type that is contained on the clutch disc don’t go well together.

The clutch disc friction material actually begins to soak up the engine oil like a sponge. A slippery spongy clutch is the opposite of what you need to move the vehicle properly.

This type of clutch problem is actually quite common and happens to many manual transmission vehicles from manufacturers both foreign and domestic.

300ZX Flywheel Problems

I pulled the transmission and remove the clutch and pressure plate. I could see there was some heat scoring and a bluish color to the flywheel surface. I decided to send the flywheel out to be resurfaced at a local machine shop.

OEM Clutch Kit
OEM Clutch Kit

Since I wasn’t into racing at the time I just decided to go with a standard clutch kit that included a new pressure plate and throw out bearing. I got the flywheel back and it looked very nice. I put it all back together with the new rear main seal and although the clutch moved the vehicle it would slip under heavy loads.

I suspected that the pressure plate from the cheap clutch kit was the problem. It appeared to me that there was not enough clamping force. When I pulled the transmission back out and once again removed the clutch and pressure plate the flywheel surface was again a bluish color.

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I called the supplier of the clutch kit and told them what was going on. The first question they asked was, did I have the flywheel resurfaced. They suggested I check the thickness of the flywheel to make sure it was not over machined.

I never thought to check the work of the machine shop. But that was exactly the case. They took too much off the flywheel surface and it was now undersized. After purchasing a new flywheel and talking the clutch kit supplier into sending me a new friction disc I put it back together. Problem solved the clutch had full grabbing power and no slippage.

More Nissan 300ZX Clutch Problems

After about two weeks of happy driving I was at a stoplight and had the clutch pedal depressed to the floor and the gear selector in first waiting for the light to turn green. I felt the clutch pedal starting to fade and the car started to move forward.

Clutch master cylinder
Clutch master cylinder

I popped it in neutral and pumped the clutch pedal and it returned to normal. This began to happen more often. The clutch was fading just like a brake pedal does when a brake master cylinder is failing. The clutch master cylinder is very similar to a brake system one.

To shorten a long story, after my clutch job as described above, it was necessary for me to bleed the hydraulic clutch system. However, I got distracted and left the master cylinder cover off for several hours. The clutch hydraulic system uses brake fluid that is considered to be hydroscopic. It absorbs moisture quickly.

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With the clutch hydraulic fluid contaminated it destroyed the seals in both the slave cylinder and the clutch master cylinder. Since the hydraulic hose that connected the two cylinders is also made of rubber I decided to replace that as well. This turned out to be the most expensive clutch job I have ever seen in my 25 years in the auto repair business and it happened to be on my own car.

The 300ZX can be a very unforgiving automobile. I never owned a car that I loved so much and yet had so many problems with. In the defense of Nissan products, I did buy the vehicle 10 years old and with 100,000 miles on it. I expected it to be a hobby car. It actually turned out to be a vehicle that taught me a lot of lessons.

If you’re interested in what other lessons this vehicle taught me you can visit my 300ZX repairs page to see the ever growing list of what went wrong and how I fixed it. If you’re interested in seeing the latest posts this next link will take you back to the auto repair information blog.