QUESTION
My mechanic has just fitted a brand new clutch assembly to my Lotus Esprit Turbo.
This is a European specification Lotus Esprit I personally imported into Australia.
Its a 1991 model fitted with a turbo, Renault gearbox and Dellorto carburettors.
Now the new clutch has been installed, the pedal operation is poor as the clutch take-up point is very close to the floor.
Is this correct or are there some adjustments to be made?
R.A. - Palm Beach, NSW, Australia
ANSWER.
The new clutch bite-point (take-up point) will be very different to the worn clutch.
The old worn clutch would have had a typical bite-point approaching the end of the upward pedal travel.
A large amount of pedal travel before the clutch engages, indicates a worn friction plate that should be changed before slippage occurs.
If clutch slippage is experienced then it could be for several reasons -
1) oil contamination on friction plate - caused by faulty/leaking crankshaft rear main seal
2) overheated friction material on driven plate - caused by clutch abuse
3) minimal thickness of friction material exposing fixing rivets - caused by normal wear
For diagnosis of other clutch related problems, see the comprehensive diagnostic trouble-shooting information charts
A newly installed clutch will have a take-up point closer to the floor.
If the clutch engages instantly when the pedal is released from the fully depressed position, then this should be investigated.
There are a number of checks and possible adjustments to be made.
First, the clutch hydraulic system should be bled to ensure there are no air-locks and that it has fresh fluid in the system.
It is recommended that 100ml to 250ml of fresh fluid be pumped through the system to completely flush out the old hydraulic fluid.
To ensure a superior pedal response at elevated temperatures, Lotus Marques recommends replacing the existing plastic hose and installing a stainless steel braided hose kit.
Next, check the pedal operation by looking for excessive movement in the push-rod and clevis pin as this indicates component wear.
This is best achieved by observing the clevis pin movement at the pedal connecting point.
Wear on the clevis pin and push-rod eye will be seen as excessive free-play.
If these components are badly worn, then this will reduce the effective stroke/movement at the clutch fork.
It maybe necessary to replace both these items to eliminate the excessive movement.
Next, check and adjust the clutch master cylinder push-rod length to achieve the pedal clearance stated below.
Next, adjust the pedal up-stop to the manufacturers specifications below.
Next adjust the clutch fork push-rod and lock nut to the manufacturers specifications below.
To assist in the checks and adjustments, the following information has been extracted directly from Lotus Service Notes ... Section QC
QC.1 - GENERAL DESCRIPTION
This section covers the following vehicles:-
- 1988 M.Y. USA Esprit Turbo - Citroen based transmission
- 1988 M.Y. onwards Domestic/Export )
Esprit & Esprit Turbo) - Renault based transmission
- 1989 M.Y. onwards USA Esprit Turbo )
The clutch consists of a single dry driven friction plate clamped between the pressure plate and flywheel by a diaphragm spring.
The friction plate incorporates six coil springs to absorb transmission shock loads and is free to slide along the splines of a clutch shaft whose rear end is splined to the gearbox primary shaft and whose front end is supported by a needle roller bearing (Citroen based transmission) or ball bearing race (Renault based transmission) in the rear end of the crankshaft.
The pressure plate and diaphragm spring are incorporated into a single non-serviceable clutch cover assembly.
The clutch release mechanism is hydraulically operated via a master cylinder at the pedal box and slave cylinder mounted on the clutch bell-housing.
The release fork, pivoted on a fulcrum pin inside the clutch housing, moves a sealed ball bearing against the fingers of the diaphragm spring.
The release bearing is mounted on a carrier which on Citroen based transmissions, slides inside, and on Renault based transmissions outside, a guide tube clamped between the clutch housing and gearbox.
QC. 2 - ADJUSTMENT
Pedal Adjustment
1. With the clutch pedal fully depressed and the master cylinder bottoming out, check the clearance between the lower edge of the clutch pedal pad (metal) and the GRP body.
If necessary, adjust the clutch master cylinder push-rod length to achieve a clearance of 2 - 5 mm, i.e. the pedal should just touch the carpet..
2. With the clutch pedal released, adjust the pedal up-stop (if fitted), or discard if necessary to achieve 2 - 5 mm upward free play on the pedal, i.e. the master cylinder is 'topping out'.
If the master cylinder piston is restricted from reaching its full travel in either direction, clutch drag and/or slip will result.
Ensure that the clutch push-rod is connected to the clutch pedal upper hole. 'C' (clutch) and not the lower hole 'B' (brake).
If necessary, adjust the brake pedal up-stop and push-rod length to obtain compatible pedal heights.
Thus set up the clutch pedal should require adjustment only after replacement of a pedal box component.
Release Fork Adjustment
The clutch slave cylinder is self adjusting, with more fluid being returned to the master cylinder as the friction plate wears in service and the slave cylinder piston is pushed progressively further back on its return stroke.
The "adjuster" in the release fork end should be set such that the specified amount of adjuster projects beyond the lock-nut as shown in the diagram.
This dimension has been selected to allow the maximum permissible wear of the friction plate to take place before the slave cylinder 'tops out' on its return stroke causing clutch slip and indicating that clutch replacement is necessary.
A smaller dimension may result in damage being caused to the pressure plate whilst a larger dimension will not fully utilise the friction plate material thickness.
QC.3 - HYDRAULIC UNITS
Master Cylinder
The Girling Centre Valve (C.V.) type master cylinder operates as follows:
When the clutch pedal is depressed, the push rod contacts the plunger and pushes it up the bore of the cylinder.
During the first 0.8mm of movement, the spring washer fitted under the valve head is allowed to resume its natural 'bowed' shape, and closes the port to the reservoir.
As the plunger continues to move up the bore, fluid is forced through the pipe to the slave cylinder.
On the return stroke, the plunger moves back with the return of the fluid, the final movement of the plunger pulling the valve stem and compressing the spring washer.
This causes the valve seal to be lifted off its seat, opening the reservoir port and allowing free passage of fluid between system and reservoir.
My mechanic has just fitted a brand new clutch assembly to my Lotus Esprit Turbo.
This is a European specification Lotus Esprit I personally imported into Australia.
Its a 1991 model fitted with a turbo, Renault gearbox and Dellorto carburettors.
Now the new clutch has been installed, the pedal operation is poor as the clutch take-up point is very close to the floor.
Is this correct or are there some adjustments to be made?
R.A. - Palm Beach, NSW, Australia
ANSWER.
The new clutch bite-point (take-up point) will be very different to the worn clutch.
The old worn clutch would have had a typical bite-point approaching the end of the upward pedal travel.
A large amount of pedal travel before the clutch engages, indicates a worn friction plate that should be changed before slippage occurs.
If clutch slippage is experienced then it could be for several reasons -
1) oil contamination on friction plate - caused by faulty/leaking crankshaft rear main seal
2) overheated friction material on driven plate - caused by clutch abuse
3) minimal thickness of friction material exposing fixing rivets - caused by normal wear
For diagnosis of other clutch related problems, see the comprehensive diagnostic trouble-shooting information charts
A newly installed clutch will have a take-up point closer to the floor.
If the clutch engages instantly when the pedal is released from the fully depressed position, then this should be investigated.
There are a number of checks and possible adjustments to be made.
First, the clutch hydraulic system should be bled to ensure there are no air-locks and that it has fresh fluid in the system.
It is recommended that 100ml to 250ml of fresh fluid be pumped through the system to completely flush out the old hydraulic fluid.
To ensure a superior pedal response at elevated temperatures, Lotus Marques recommends replacing the existing plastic hose and installing a stainless steel braided hose kit.
Next, check the pedal operation by looking for excessive movement in the push-rod and clevis pin as this indicates component wear.
This is best achieved by observing the clevis pin movement at the pedal connecting point.
Wear on the clevis pin and push-rod eye will be seen as excessive free-play.
If these components are badly worn, then this will reduce the effective stroke/movement at the clutch fork.
It maybe necessary to replace both these items to eliminate the excessive movement.
Next, check and adjust the clutch master cylinder push-rod length to achieve the pedal clearance stated below.
Next, adjust the pedal up-stop to the manufacturers specifications below.
Next adjust the clutch fork push-rod and lock nut to the manufacturers specifications below.
To assist in the checks and adjustments, the following information has been extracted directly from Lotus Service Notes ... Section QC
QC.1 - GENERAL DESCRIPTION
This section covers the following vehicles:-
- 1988 M.Y. USA Esprit Turbo - Citroen based transmission
- 1988 M.Y. onwards Domestic/Export )
Esprit & Esprit Turbo) - Renault based transmission
- 1989 M.Y. onwards USA Esprit Turbo )
The clutch consists of a single dry driven friction plate clamped between the pressure plate and flywheel by a diaphragm spring.
The friction plate incorporates six coil springs to absorb transmission shock loads and is free to slide along the splines of a clutch shaft whose rear end is splined to the gearbox primary shaft and whose front end is supported by a needle roller bearing (Citroen based transmission) or ball bearing race (Renault based transmission) in the rear end of the crankshaft.
The pressure plate and diaphragm spring are incorporated into a single non-serviceable clutch cover assembly.
The clutch release mechanism is hydraulically operated via a master cylinder at the pedal box and slave cylinder mounted on the clutch bell-housing.
The release fork, pivoted on a fulcrum pin inside the clutch housing, moves a sealed ball bearing against the fingers of the diaphragm spring.
The release bearing is mounted on a carrier which on Citroen based transmissions, slides inside, and on Renault based transmissions outside, a guide tube clamped between the clutch housing and gearbox.
QC. 2 - ADJUSTMENT
Pedal Adjustment
1. With the clutch pedal fully depressed and the master cylinder bottoming out, check the clearance between the lower edge of the clutch pedal pad (metal) and the GRP body.
If necessary, adjust the clutch master cylinder push-rod length to achieve a clearance of 2 - 5 mm, i.e. the pedal should just touch the carpet..
2. With the clutch pedal released, adjust the pedal up-stop (if fitted), or discard if necessary to achieve 2 - 5 mm upward free play on the pedal, i.e. the master cylinder is 'topping out'.
If the master cylinder piston is restricted from reaching its full travel in either direction, clutch drag and/or slip will result.
Ensure that the clutch push-rod is connected to the clutch pedal upper hole. 'C' (clutch) and not the lower hole 'B' (brake).
If necessary, adjust the brake pedal up-stop and push-rod length to obtain compatible pedal heights.
Thus set up the clutch pedal should require adjustment only after replacement of a pedal box component.
Release Fork Adjustment
The clutch slave cylinder is self adjusting, with more fluid being returned to the master cylinder as the friction plate wears in service and the slave cylinder piston is pushed progressively further back on its return stroke.
The "adjuster" in the release fork end should be set such that the specified amount of adjuster projects beyond the lock-nut as shown in the diagram.
This dimension has been selected to allow the maximum permissible wear of the friction plate to take place before the slave cylinder 'tops out' on its return stroke causing clutch slip and indicating that clutch replacement is necessary.
A smaller dimension may result in damage being caused to the pressure plate whilst a larger dimension will not fully utilise the friction plate material thickness.
QC.3 - HYDRAULIC UNITS
Master Cylinder
The Girling Centre Valve (C.V.) type master cylinder operates as follows:
When the clutch pedal is depressed, the push rod contacts the plunger and pushes it up the bore of the cylinder.
During the first 0.8mm of movement, the spring washer fitted under the valve head is allowed to resume its natural 'bowed' shape, and closes the port to the reservoir.
As the plunger continues to move up the bore, fluid is forced through the pipe to the slave cylinder.
On the return stroke, the plunger moves back with the return of the fluid, the final movement of the plunger pulling the valve stem and compressing the spring washer.
This causes the valve seal to be lifted off its seat, opening the reservoir port and allowing free passage of fluid between system and reservoir.