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The Ranger Clutch Fluid Protocol
The Problem
When driven aggressively, GM cars with manual transmissions and the LS1, LS2, LS6, and LS7 engines sometimes fall prey to clutch pedal issues during or following high-rpm shifts.
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.
Massimiliano's Music will be featured on Ranger's DVD
Powered by iSOUND.COM
The Cause
Over the years various theories have been advanced on the root cause of pedal woes. There is no agreement, but one theme does seem clear. Faced with pedal woes, replacing all clutch and hydraulic components with new stock parts does not prevent a quick return of the same symptoms, if the car continues to be driven aggressively. And on tear-down inspection, none of the parts shows any indication of failure.
After GM’s “replace all parts” approach failed to solve pedal woes on my 2001 Z06, I sought an effective remedy. I found through experimentation that keeping the clutch fluid fresh and clean resolves or prevents most pedal woes. In fact, my pedal woes disappeared entirely when I began keeping the clutch fluid clean. Three Z06s and 570 passes at the drag strip later, my clutch fluid remains clean, due to the protocol, and my clutch has behaved normally.
What Does the Clutch Fluid Have to Do with Pedal Woes?
The simple answer is the ravage of heat and water. Clutch fluid is actually brake fluid. It degrades when subjected to high heat produced during aggressive driving and to water absorption. When heated enough, degraded fluid will boil its water content and emit a gas or steam. In the hydraulic system gas compresses under pressure, unlike fluid, and causes the malfunction of parts that depend on an unachieved hydraulic pressure value.
In the prevailing GM clutch design the clutch actuator cylinder (slave) is located inside the bell housing. That location puts clutch fluid in close proximity to very high heat,
especially
during launches and high-rpm shifts that necessarily entail
slippage of the friction surfaces between the pressure plate,
clutch disc, and flywheel. These bursts of friction-induced high
heat are sufficient to boil clutch fluid if its boiling point has
been degraded significantly from the nominal specification on the
can.
The
classic indication of degraded fluid is a change in color from
nearly clear to dark and murky. When it reaches that state, the
fluid should be cleaned up. If that’s not done, normal operation of
the clutch hydraulics will be disrupted under high demand
circumstances. This can cause incomplete disengagement of the
clutch during high-rpm shifts, which in turn can lead to
missed-shifts that damage the transmission.
Road
racers know they must bleed the brake fluid frequently to keep
their brakes from misbehaving during track sessions. Why does
anyone think that the brake fluid in the clutch is any
different?
The Goal
Keep the fluid in your clutch hydraulics 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 a temperature high enough to make the fluid boil, the origin of pedal woes.
Murkiness is the tell that fluid is degrading. The darker the fluid is when agitated, the lower its boiling point is. Under aggressive driving that includes high-rpm strong shifts, the temp at the slave can exceed 400F. If the fluid is degraded from its nominal 500F dry boiling point, the margin of error is diminished. The GM-branded Super-DOT4 fluid will boil at 336 degrees when "wet" (3% water by volume) a condition easily met with repeated heat/cool cycles of the fluid that yield condensation.
As a guide, consider the degradation that brake fluid takes in a couple 30 minute track sessions. That's why it gets bled daily, to avoid brake pedal woes. Conceptually, clutch fluid is no different.
The Protocol Steps
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 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) Replace the reservoir cap snugly.
Step 3
With the engine off, pump the clutch pedal rapidly and strongly 20-30 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 .
Step 4
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 aggressive pedal pumps between changes, until it remains absolutely clear and clean.
Step 5
Then 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 (2).
Even badly degraded, dirty clutch fluid can be substantially cleaned up in ten or so 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 LSx 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.
Which Clutch Fluid to Use?
You can’t go wrong by using the clutch fluid specified in your owner’s manual. That’s a GM-branded fluid.
When considering alternative brands, keep in mind there is no magic fluid that prevents pedal woes. All fluids will degrade under aggressive driving and need changing regularly.
If you want an alternative to the GM-branded fluid, I’ve used Prestone brand with good results for six years in three Z06s. That means, following the fluid change protocol with Prestone, I’ve had no clutch pedal issue. I am currently using Prestone DOT4 Synthetic in my 2006 Z06. But I have no reason to believe that my results would be different with any other good brand, so long as the protocol is followed.
If you want to upgrade your clutch fluid, DOT4 is usually compatible with the DOT3. But be sure to read the label on cans you’re considering. DOT4 brake fluid generally has higher dry and wet boiling points than DOT3. Given the minimal price difference between the two, it makes sense to use DOT4.
Here
an excellent chart of alternative high-quality fluids, linked by
permission of Seine Systems. In this chart, note that Pentosin
Super DOT4 brake fluid is repackaged and distributed under the
GM-brand and is specified for C6 Corvettes clutch
hydraulics.
The Syringe
For
removing the dirty clutch fluid, I use a syringe that’s made for
mixing oil and gasoline used in two-stroke motors. It has given
good service for six years without leaking. Some prefer medical
syringes; others still like a turkey baster. I prefer a syringe
because it’s reliable, compact and doesn’t
leak.
Lint-Free Towels
For cleaning the reservoir and rubber diaphragm, I use blue paper towels intended for car detailing. They are thick, absorbent and disposable.
A Clutch Fluid Change Kit
In my car I carry a clutch fluid changing kit with the following components:
• Can of fresh brake fluid
• Can for storing spent fluid
• Syringe for drawing fluid from the reservoir
• Small funnel to get a precise pour in dim light
• Cup to hold the syringe and some lint-free paper towels
• Two one-gallon zip-lock freezer bags for storing the entire kit. One bag is inside the other gives a little extra protection against leakage
Alternative Approaches
There are five alternatives to adopting this protocol.
Alternative 1. Refrain from aggressive driving and high-rpm shifts. This is the automotive equivalent of abstinence. It’s also an explanation of why many owners never suffer pedal woes…they don’t drive aggressively.
Alternative 2. Complain to the dealer about your clutch pedal issue. If your car is under warranty, the GM remedy may be invoked, which is swapping all the clutch parts. That may sound great. But keep in mind a clutch swap entails risk, unless the servicing tech is experienced and meticulous in following correct procedures. Plus, the new parts may not be properly balanced. I've lost track of how many owners I've counseled through vibration issues after botched clutch installs.
Alternative 3. Have the clutch hydraulics bled. This takes a competent technician about an hour and requires a lift. Cost is around $125. But the procedure includes some inherent difficulties:
• A hard, constricted reach with a tool to loosen the bleeder valve in its barely accessible position.
• A messy job because fluid dribbles over adjacent surfaces.
• Requires two people, one at the bleeder valve, the other at the clutch pedal; or, if using a pump tool, the other keeping the clutch reservoir filled.
• if not done right, residual air will remain in the hydraulics, causing continued pedal issues.
• if crud has built up in the actuator (slave), a simple bleed won't dislodge it.
• Under the best of circumstances, the clutch will need bleeding each time the clutch fluid deteriorates. No cheap.
Some owner install a remote bleeder valve in the engine bay to simplify a full bleed of the clutch hydraulics. This is a good modification to make when replacing a clutch. At the same time, insulating the clutch hydraulic lines thoroughly can partially mitigate the adverse impact of heat.
Alternative 4. Change to an aftermarket clutch and hope for relief. Unfortunately, some aftermarket clutches suffer pedal woes too, particularly those using stock GM clutch hydraulic components (clutch master cylinder and clutch actuator cylinder (the slave). This is especially true if the clutch fluid is not given preventative maintenance.
Alternative 5. Do nothing and suffer continued clutch issues which often give rise to transmission damage.
Other Clutch Issues
Pedal issues on high-rpm shifts are largely the result of deteriorated clutch fluid. But they can also result from poorly timed clutch engagement (clutch-out) on the shift, causing excessive slippage.
Pedal issues on launch are generally caused by driver technique error--too slow a pedal release while the throttle is engaged.
The C6Z06's LS7 clutch, even with clean fluid, will glaze on launch or a sloppy shift if the clutch is slipped, intentionally or not, by a slow release at elevated rpm, say above 2500. In such an event, the friction surfaces overheat from the slip to such an extent that the nominal clamping power of the clutch is lost; and the clutch pedal usually hangs mid-way up. There is no widely accepted explanation of this behavior’s exact cause. But it is an annoying flaw in the LS7 personality. If you want to ensure an LS7 launch without clutch issues, keep the launch rpm at 3600 or less and make a very fast clutch release, with the clutch foot coming up in a single motion. Since learning that lesson, I've not glazed the clutch in my car.
A WARNING on clutches that are slipping under load.
As you add horsepower/torque to a motor, the load may eventually surpass the rated clamping-force of the existing clutch. Once that happens, the friction surfaces will slip excessively in high-demand circumstances, producing even more heat than normal. These heat loads can cause malfunction of the slave.
A slipping clutch placed under the demands of launch and strong shifts may suffer a catastrophic failure. You may have seen pictures of those events. Quite ugly and not warrantied by anyone. Last one I saw cost the car owner $13K in out-of-pocket repairs. Pressure plate exploded; clutch fluid sprayed the headers causing a fire. Not a happy ending.
Moral of the story. Know the limits of your clutch and don't exceed them. If the clutch is slipping, get a new one with appropriate clamping power.
The Problem
When driven aggressively, GM cars with manual transmissions and the LS1, LS2, LS6, and LS7 engines sometimes fall prey to clutch pedal issues during or following high-rpm shifts.
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.
Massimiliano's Music will be featured on Ranger's DVD
Powered by iSOUND.COM
The Cause
Over the years various theories have been advanced on the root cause of pedal woes. There is no agreement, but one theme does seem clear. Faced with pedal woes, replacing all clutch and hydraulic components with new stock parts does not prevent a quick return of the same symptoms, if the car continues to be driven aggressively. And on tear-down inspection, none of the parts shows any indication of failure.
After GM’s “replace all parts” approach failed to solve pedal woes on my 2001 Z06, I sought an effective remedy. I found through experimentation that keeping the clutch fluid fresh and clean resolves or prevents most pedal woes. In fact, my pedal woes disappeared entirely when I began keeping the clutch fluid clean. Three Z06s and 570 passes at the drag strip later, my clutch fluid remains clean, due to the protocol, and my clutch has behaved normally.
What Does the Clutch Fluid Have to Do with Pedal Woes?
The simple answer is the ravage of heat and water. Clutch fluid is actually brake fluid. It degrades when subjected to high heat produced during aggressive driving and to water absorption. When heated enough, degraded fluid will boil its water content and emit a gas or steam. In the hydraulic system gas compresses under pressure, unlike fluid, and causes the malfunction of parts that depend on an unachieved hydraulic pressure value.
In the prevailing GM clutch design the clutch actuator cylinder (slave) is located inside the bell housing. That location puts clutch fluid in close proximity to very high heat,
The Goal
Keep the fluid in your clutch hydraulics 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 a temperature high enough to make the fluid boil, the origin of pedal woes.
Murkiness is the tell that fluid is degrading. The darker the fluid is when agitated, the lower its boiling point is. Under aggressive driving that includes high-rpm strong shifts, the temp at the slave can exceed 400F. If the fluid is degraded from its nominal 500F dry boiling point, the margin of error is diminished. The GM-branded Super-DOT4 fluid will boil at 336 degrees when "wet" (3% water by volume) a condition easily met with repeated heat/cool cycles of the fluid that yield condensation.
As a guide, consider the degradation that brake fluid takes in a couple 30 minute track sessions. That's why it gets bled daily, to avoid brake pedal woes. Conceptually, clutch fluid is no different.
The Protocol Steps
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 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) Replace the reservoir cap snugly.
Step 3
With the engine off, pump the clutch pedal rapidly and strongly 20-30 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 .
Step 4
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 aggressive pedal pumps between changes, until it remains absolutely clear and clean.
Step 5
Then 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 (2).
Even badly degraded, dirty clutch fluid can be substantially cleaned up in ten or so 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 LSx 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.
Which Clutch Fluid to Use?
You can’t go wrong by using the clutch fluid specified in your owner’s manual. That’s a GM-branded fluid.
When considering alternative brands, keep in mind there is no magic fluid that prevents pedal woes. All fluids will degrade under aggressive driving and need changing regularly.
If you want an alternative to the GM-branded fluid, I’ve used Prestone brand with good results for six years in three Z06s. That means, following the fluid change protocol with Prestone, I’ve had no clutch pedal issue. I am currently using Prestone DOT4 Synthetic in my 2006 Z06. But I have no reason to believe that my results would be different with any other good brand, so long as the protocol is followed.
If you want to upgrade your clutch fluid, DOT4 is usually compatible with the DOT3. But be sure to read the label on cans you’re considering. DOT4 brake fluid generally has higher dry and wet boiling points than DOT3. Given the minimal price difference between the two, it makes sense to use DOT4.
The Syringe
Lint-Free Towels
For cleaning the reservoir and rubber diaphragm, I use blue paper towels intended for car detailing. They are thick, absorbent and disposable.
A Clutch Fluid Change Kit
In my car I carry a clutch fluid changing kit with the following components:
• Can of fresh brake fluid
• Can for storing spent fluid
• Syringe for drawing fluid from the reservoir
• Small funnel to get a precise pour in dim light
• Cup to hold the syringe and some lint-free paper towels
• Two one-gallon zip-lock freezer bags for storing the entire kit. One bag is inside the other gives a little extra protection against leakage
Alternative Approaches
There are five alternatives to adopting this protocol.
Alternative 1. Refrain from aggressive driving and high-rpm shifts. This is the automotive equivalent of abstinence. It’s also an explanation of why many owners never suffer pedal woes…they don’t drive aggressively.
Alternative 2. Complain to the dealer about your clutch pedal issue. If your car is under warranty, the GM remedy may be invoked, which is swapping all the clutch parts. That may sound great. But keep in mind a clutch swap entails risk, unless the servicing tech is experienced and meticulous in following correct procedures. Plus, the new parts may not be properly balanced. I've lost track of how many owners I've counseled through vibration issues after botched clutch installs.
Alternative 3. Have the clutch hydraulics bled. This takes a competent technician about an hour and requires a lift. Cost is around $125. But the procedure includes some inherent difficulties:
• A hard, constricted reach with a tool to loosen the bleeder valve in its barely accessible position.
• A messy job because fluid dribbles over adjacent surfaces.
• Requires two people, one at the bleeder valve, the other at the clutch pedal; or, if using a pump tool, the other keeping the clutch reservoir filled.
• if not done right, residual air will remain in the hydraulics, causing continued pedal issues.
• if crud has built up in the actuator (slave), a simple bleed won't dislodge it.
• Under the best of circumstances, the clutch will need bleeding each time the clutch fluid deteriorates. No cheap.
Some owner install a remote bleeder valve in the engine bay to simplify a full bleed of the clutch hydraulics. This is a good modification to make when replacing a clutch. At the same time, insulating the clutch hydraulic lines thoroughly can partially mitigate the adverse impact of heat.
Alternative 4. Change to an aftermarket clutch and hope for relief. Unfortunately, some aftermarket clutches suffer pedal woes too, particularly those using stock GM clutch hydraulic components (clutch master cylinder and clutch actuator cylinder (the slave). This is especially true if the clutch fluid is not given preventative maintenance.
Alternative 5. Do nothing and suffer continued clutch issues which often give rise to transmission damage.
Other Clutch Issues
Pedal issues on high-rpm shifts are largely the result of deteriorated clutch fluid. But they can also result from poorly timed clutch engagement (clutch-out) on the shift, causing excessive slippage.
Pedal issues on launch are generally caused by driver technique error--too slow a pedal release while the throttle is engaged.
The C6Z06's LS7 clutch, even with clean fluid, will glaze on launch or a sloppy shift if the clutch is slipped, intentionally or not, by a slow release at elevated rpm, say above 2500. In such an event, the friction surfaces overheat from the slip to such an extent that the nominal clamping power of the clutch is lost; and the clutch pedal usually hangs mid-way up. There is no widely accepted explanation of this behavior’s exact cause. But it is an annoying flaw in the LS7 personality. If you want to ensure an LS7 launch without clutch issues, keep the launch rpm at 3600 or less and make a very fast clutch release, with the clutch foot coming up in a single motion. Since learning that lesson, I've not glazed the clutch in my car.
A WARNING on clutches that are slipping under load.
As you add horsepower/torque to a motor, the load may eventually surpass the rated clamping-force of the existing clutch. Once that happens, the friction surfaces will slip excessively in high-demand circumstances, producing even more heat than normal. These heat loads can cause malfunction of the slave.
A slipping clutch placed under the demands of launch and strong shifts may suffer a catastrophic failure. You may have seen pictures of those events. Quite ugly and not warrantied by anyone. Last one I saw cost the car owner $13K in out-of-pocket repairs. Pressure plate exploded; clutch fluid sprayed the headers causing a fire. Not a happy ending.
Moral of the story. Know the limits of your clutch and don't exceed them. If the clutch is slipping, get a new one with appropriate clamping power.