Clutch Maintenance

[fnkngrv]

This is something that a lot of folks forget with a manual transmission to work toward a smooth running clutch and is cheap/easy to do.

The Problem

When driven aggressively, economy cars with manual transmissions and boosted engines sometimes fall prey to clutch pedal issues during or following high-rpm shifts. For clarity sake, driven “aggressively” means cars that are launched or see high-rpm up-shifts or down-shifts. And consequential clutch problems affect many brands of cars and motorcycles too.


The general symptoms include a clutch pedal that becomes
• Hard
• Soft
• Slow to return or lazy
• Hung mid-way up or
• Stuck to the floor

These misbehaviors are commonly called clutch pedal “woes.”

The Cause
Over the years various theories have been advanced on the root cause of pedal woes. There is no broad agreement, but one fact does seem to remain constant.

Faced with pedal woes, replacing all clutch and hydraulic components with new stock parts does not prevent a quick return of the same symptoms in a car driven aggressively. And upon tear-down inspection, none of the parts shows obvious failure.

Through experimentation, I found that keeping the clutch fluid fresh and clean prevented a recurrence of pedal woes in my use. Three 1NZs and 50 passes at the land speed strip later, my clutches have behaved normally due to my keeping the clutch fluid clean, via to the protocol I recommend.

Preventative maintenance (frequent swaps of the fluid via the master cylinder reservoir) definitely works. It also explains why, if the seals are already damaged by clutch dust, no amount of clean fluid will heal them. The crucial element is prevention, never allowing the clutch dust to accumulate in the fluid. The tell of its presence is murkiness or cloudiness. So don’t allow the fluid to stay murky.

I think water entering the fluid via heat-cool cycles plays a roll in clutch pedal issues. So frequent changes of the clutch fluid ought to be part of routine maintenance for owners who don’t do aggressive launch or shifts.

The routine I personally follow costs about $20 and two hours of my time per year. That’s a small investment with a big return in reliability and driving pleasure.

The Goal
Keep the fluid in your clutch hydraulics free of accumulated clutch dust. And Keep the fluid near the nominal dry boiling point on the can (450F to 500F, depending on the brand), and keep the fluid dry, e.g. without contamination by infusion of water.

If that is accomplished by frequent changes of the reservoir content, the clutch hydraulics will never see accumulated clutch dust nor a temperature high enough to make the fluid boil, the dual origins of pedal woes. And the seals will enjoy a long service-life, if kept free of clutch dust ravages.

Murkiness is “the tell” that fluid is degrading. The darker the fluid is when agitated, the more urgent it is for it to be cleaned up before pedal woes take hold.

The Steps I take:

Step 1
Inspect the fluid in the clutch master cylinder reservoir. If it’s not clear and clean move to step (2).

Step 2
Change the fluid in the clutch master cylinder reservoir.
(a) Draw out the discolored fluid with a syringe, keeping the corrosive fluid off your paint.
(b) Wipe down the reservoir and the diaphragm on the cap, using a clean, lint-free towel.
(c) Locate the fill-line in or on the reservoir.
(d) Refill the reservoir to just below the fill-line with fresh fluid specified in your owner’s manual. Do not over-fill. If the reservoir has both minimum and maximum marks, suggest filling to the midpoint.
(e) Clean the diaphragm if dirty and properly seat it on the reservoir cap.
(f) Replace the reservoir cap snugly.

Step 3
With the engine off, pump the clutch pedal full-top to full-bottom to full-top 30 times. This action causes fluid in the clutch hydraulics to circulate, blending the new and old fluid, and revealing the color of the blend. It also helps scour residue from the actuator (slave) and displace upward into the reservoir any air trapped in the hydraulics. Alternatively, you can drive the car 5-10 miles.

Step 4
Then, re-inspect the blended fluid in the reservoir. If it is totally clear and shows zero murkiness, you are finished. If it's not, restart at (2). Continue to change the fluid as many times as needed, with the full, slow top-to-bottom-to-top pedal pumps between changes, until it remains absolutely clear and clean. Getting the fluid clean the first time is the hard part.

Step 5
Next come the easy part, keeping it clean. Re-inspect the clutch fluid each time you add gasoline or prepare for spirited driving, including the track. If it is not still clear and clean, restart at Step-2. Usually will take only two or three swaps to get the fluid pristine again.


Even badly degraded, dirty clutch fluid can be substantially cleaned up in 10-20 reservoir changes. This takes less than an hour, costs less than $10 for fluid and a syringe, and doesn’t require a service visit. I recommend this protocol for clutches on cars with engines that see any form of aggressive driving. If you follow this protocol, you very likely will avoid clutch pedal issues. And that is a very important assurance, because the car’s performance depends on a properly operating clutch.

Even though I just about direct quoted this reference to learn more it is worth your time. He is talking about the Corvette, but I found this a few years ago and have stuck to it:


http://www.rangeracceleration.com/Clutch_Care.html

sent from my m-o-b-i-l-e