"How Clutches Work"
"Manual Transmission Clutch Troubleshooting"
"How To Replace Clutch And Clutch Related Components."
All this details including much more clutch related issues and troubleshooting will be shared below.
Clutch is actuated either by mechanical linkage,clutch cable or by hydraulic clutch system.
On mechanical linkage and clutch cable operated system the clutch pedal free-play movement has to be adjusted by time.On Hydraulic clutch system this adjustment is done automatically.But clutch pedal height adjustment is not possible.
On old cars clutch is operated by clutch cable and on newer manual transmission vehicles the clutch is operated by hydraulic pressure.
See below Basic Picture of "Clutch assembly"
Here we will discuss about all types of clutch problem noticed on a vehicle and Clutch itself.
First go through the basics clutch and its working.
"Working Of Clutch Mechanism"
Its a very important device."Clutch" has two rotating shafts.One shaft is operated by motor or puller and another shaft is spin by the first shaft.
The clutch has very interesting function,it connects two shafts together,so either the shafts will get locked or will spin together.
Clutch mechanism assembly is also called as pressure plate. Clutch assembly bolts to the flywheel and engages or disengages the clutch disc to the flywheel. Clutch is a spring-loaded device that by contact with the throw out bearing (clutch release bearing), forces the clutch disc against the flywheel when the clutch pedal is released and lets the clutch disc free wheel when the clutch pedal is depressed.
"Why Clutch Is Required?"
Its a important component or say part for a vehicle.Because as we know the engine of the vehicle always spins.And wheels of the vehicle do not.
Because when you start the car and drive the car,the engine starts functioning and this spins the wheel.The wheels are connected by engine mechanism.
So to stop the vehicle without killing the running engine,the wheels are to be disconnected from engine mechanism.And this is what clutch does,the clutch mechanism helps to smoothly engage a spinning engine to a non-spinning transmission by controlling the slippage between them.
The clutch operates by theory of friction of two objects.
For clutch the two objects are clutch plate and a flywheel.
"How To Inspect Clutch Assembly?"
Before replacing clutch assembly,its suggested to first inspect the clutch system and its related parts.
On most cases when clutch needs replacement,its the issue with pressure plate cover getting bent or broken.
The pressure plate assembly also referred clutch cover assembly is a cast iron plate that is actually part of the cover assembly.
There are two types of pressure plate assemblies:
1) One with coil springs and
2) One with a diaphragm spring.
It depend on vehicle manufacturer which he has used.Both assemblies differ in the manner in which they move the pressure plate toward and away from the clutch disc.
Now to inspect the clutch assembly you need to remove the clutch assembly.
Its not a easy a simple task.But with proper car repair knowledge and tools or with the help of car professional it can be done.
Note: To inspect clutch system,clutch assembly has to be removed and this usually requires transmission removal.
Once the transmission is out the clutch assembly can be disassembled
Inside the clutch assembly you will have to check pressure plate surface for warpage by laying a straightedge across the surface and inserting a feeler gauge between the surface and the straightedge.
Compare the measurement against the specifications given in the service manual.
Also check the release levers of the pressure plate for uneven wear or damage.
See below the image showing pressure plate warpage:
Below we have shared few clutch related common problem noticed by others and their required troubleshooting solutions:
"Clutch Slips on Hills Or During Sudden acceleration."
On such issues what you need to inspect is:- Check for Insufficient clutch pedal free-play. Adjust clutch linkage or cable to allow about 1 Inch of pedal free play.(1 Inch is 25mm).
- Inspect clutch disc,its either worn out by age or got severely damaged.On either case the clutch disc has to be replaced and for that engine or transmission has to be removed first.
- Weak Clutch Pressure plate causing clutch slip.It has to be replaced,engine or transmission has to be remove first to inspect the pressure plate and replace it.
- Clutch pressure plate and flywheel got incorrectly misaligned.If this parts got out of its actual alignment then the clutch will not operate right.
- Many a times such things are noticed after replacing clutch assembly.On this cases all has to be disassembled again and reinspected.If low quality aftermarket parts are used,they can easily get misaligned due to their low quality grip.
"Clutch Will Not Disengage And Difficult To Shift"
On such issues what you need to inspect is
- Check the clutch release mechanism.Check for overstretched clutch cables, worn out linkages, or failure of clutch hydraulics.What ever seems faulty out of this replace it.
- Also one more thing clutch operates by two ways on some car models its cable operated clutch system and on some its hydraulically operated clutch system.So on hydraulically operated clutch system,check for hydraulic pressure.If it seems or feels air in clutch system then bleed the clutch system.
- Another possibility is broken or fatigued clutch release arm or release Arm pivot.If any of this seems worn out then replace the defective parts and lubricate new parts.
- Also check clutch hub damper also called as damper spring.This parts many a times get stuck up between clutch disc and pressure plate.To inspect this part you need to disassemble clutch system and replace the faulty or defective parts.
- Also on some cases its faulty seized clutch pilot bearing.Inspect the condition of bearing.Clutch disassembly required for inspection.
- Defective clutch disc itself.To confirm this check for warpage or lining thickness quite larger then original equipment setting.
"Clutch Is Noisy When Clutch Pedal Is Pressed"
On such cases- Check for clutch pedal movement in both clutch pedal stop and free-play movement.If it seems excessive movement then required then adjust clutch pedal setting as required.
- Other possibility is faulty clutch pedal release bearing.If noise is heard while clutch pedal release then bearing is issue and it has to be replaced.
- Also check and inspect for engine crankshaft axial play.Now suppose if the crankshaft thrust bearing are worn or damaged, the crankshaft will move when clutch pedal is depressed.On that case disassemble engine and replace crank shaft thrust bearing.
"Clutch Pedal Very Hard And Difficult To Press"
On such cases the possibilities can be
- Dirty or dried up linkages.In that case lubricate the linkages.Also check the clutch pedal pivot and linkages for binding.
- Check the condition of clutch cable,if it seems bend at ends or cable not routed properly or it seems stretched then it has to be replaced.
- Also check the engine ground strap for loss of conductivity.If the engine ground strap is very marginal,then its quite possible that engine would try to ground itself through clutch cable that causes premature failure.
- Also dried up release bearing guide tube and release fork can cause stiff clutch movements.In that case lubricate this parts.One best option is to apply smooth automobile machine grease to this parts to make free movement of bearing over tube.Make sure its high temp resistant grease.
"Clutch Pedal Remains Down When Pressure"
"No Pressure In Clutch Pedal"
- Check for loose or disconnected links.Also check the condition of clutch cable.On mechanical linkage or cable operated clutch systems.
- On electrically operated clutch system,that is hydraulic mode clutch mechanism inspect for hydraulic leak at slave and master cylinders or low fluid level.In that case bleed the hydraulic clutch system,if fluid is low then refill the fluid to its correct level.Also if no leak is noticed,there can be internal fault with master cylinder.
- Master cylinder many a times fails internally and needs to be replaced. Don't forget to bleed the clutch system after replacing master cylinder.
"Clutch Makes Chattering Noise When Engaging."
On such issues Check and inspect the following possibilities:- A damaged engine flywheel or variations in its surface position.Flywheel Needs to be replaced.
- A worn out clutch disc or damaged Clutch damper hub.Clutch disc needs to be replaced.
- A loose or damaged clutch pressure plate.If its loose it can be adjusted,but if damaged clutch pressure plate has to be replaced.
"CLUTCH DISC"
Clutch disc is a spinning, circular metallic dish covered with a friction liner and held in between the flywheel and pressure plate. The splines in the core mesh with the splines on the transmission input shaft. This permits the disc and transmission input shaft to rotate together. However, the disc is free to move backwards and forwards on the input shaft.See how a basic Automobile Clutch disc looks:
Inspect the condition of clutch disc before replacing it.A worn out damaged clutch disc can cause many clutch related issues.
A complete check up of the clutch disc can point out the actual reason behind failure.
For instance, if the hub is uniformly broken away from the disc, a faulty or missing pilot bearing could be the cause. This would result from poor alignment of the transmission to the engine.
Even though the disc must be removed for a complete inspection, you can easily inspect it by taking away the flywheel inspection cover.
The best indication is Look for signs of oil and metal or lining materials on the inspection cover or bell housing.
Evidence of any of these signifies that the disc should be replaced.
Please note if the linings are oil soaked, repair the oil leak prior to installing the new disc. Change any disc that reveals signs of overheating, indicated by a blueing of the steel disc backing or double glazing of the linings.
Safety Warnings:
******** Clutch discs contain asbestos material.Asbestos is very harmful to health.It causes cancer.Never blow out clutch dust with compressed air blower and breathe the dust.Wash hands after finishing clutch repair jobs or wear gloves when working on clutch repair jobs. ********
If the disc checks out to be ok, inspect its torsion dampener springs, which dampen or cushion the input shaft and drive train from harsh engagement when the clutch is used.
Thoroughly inspect the disc's torsional coil springs.
These springs are positioned in between the friction facing and the splines of the input shaft. Try to spin the dampener springs with your finger. They should rotate, but not easily, replace the disc.
Generally a clutch disc used for more than 50,000 miles that is removed for other vehicle work should be replaced, regardless of its condition. The time and labor saved by exchanging the disc will help the client.
"How To Replace Clutch Disc"
Clutch assembly is mounted to the flywheel.The flywheel mounted to the rear of crankshaft.NOTE: Its not necessary to remove engine out.Because clutch assembly can be removed with engine in or out.Before taking apart the clutch, ensure that alignment positioning marks are present on the pressure plate and flywheel.
Before taking apart the clutch, ensure that alignment positioning marks are present on the pressure plate and flywheel.
The connecting bolts should be loosened before removing any of the bolts. With the bolts loose, assist the assembly with one hand while using the other to remove the bolts. Once the bolts are out the clutch disc will be free to slide as the pressure plate is split up from the flywheel. Keep it intact with the pressure plate without moving from its actual position.
Now first inspect condition of pressure plate. Examine the work surface of pressure plate for indications of burning, warpage, and cracks. Any faults commonly signify that the plate should be changed.
In the same way surface of the flywheel should also be carefully inspected.
Usually the flywheel surface can be resurfaced to remove any imperfections.
After pressure plate and flywheel, pilot bushings/bearing should also be inspected.
Now while replacing clutch disc carefully insert the new clutch disc into the pressure plate as the pressure plate is moved to its proper location.
Make sure the disc is facing the correct direction as it was while removal. So its always advisable to note down the clutch disc position. Most are marked to indicate which side should be seated against the flywheel surface.
Now install the pressure plate according to the alignment marks made during dis-assembly Please don't ignore marking the exact position of parts while removal, otherwise while assembly you will get confused and totally blank.
Now inspect the bolts which you have removed,if the bolts look bit worn out and very old rusted type,go for new bolts. Grease the bolt threads and install the attaching bolts, but do not tighten the bolts. First install the clutch alignment tool through the hub of the disc and the pilot bearing. This will center the disc on the flywheel.
With the disc aligned, tighten the attaching bolts.
"Clutch Bearing"
Clutch bearing is very important part of clutch working system.A bearing that lowers friction between the clutch fork and the pressure plate. It is shifted to the middle of the pressure plate triggering the pressure plate to pull away from the clutch disc, releasing the clutch disc from the flywheel.As soon the the pedal is released, spring pressure within the pressure plate drives ahead on the clutch disc to lock the disc, flywheel and pressure plate jointly. The engine may then spin the transmission shaft and gears, the drivetrain and the vehicle's wheels.
Before replacing clutch bearing, inspect its actual condition to confirm the bearing issue.
This is how clutch bearing seems to look:
Check Clutch release bearings by turning the bearing.Apply force to the bearing in the direction of rotation.
If it makes rubbing or clicking/ clunking noise then its a indication of worn out bearing.
Another possibility if you notice release bearing noise with the clutch fully engaged, the cause may be a release bearing on transmission bearing retainer, on such case, clean, relubricate, and check for burrs, dings, etc.
If you have a noisy bearing, the clutch bearing might be worn and it has to be replaced.
"How To Replace Clutch Bearing"
Once its confirmed that issue is with clutch bearing,it has to be replaced to avoid further damage to clutch mechanism.To replace clutch bearing the engine and transmission has to be separated from each other.
After that to release the clutch retainer bearing just disconnect the clutch release fork.( To know about clutch release fork and its working,continue reading after clutch bearing).
Release bearing is seated in clutch release fork,while installation make sure you properly reseat release bearing in clutch release fork.
One more important thing,while installing clutch release bearing,dont apply any additional lubrication materials like machine oil or grease,all required lubrication comes with new release bearing.You just have to fit new bearing.
But yes you can apply high quality high temperature grease to prevent the release bearing from binding on the bearing retainer or release fork.But just apply it to the bearings collar.Do not let the grease to reach the friction surfaces of the disc, pressure plate, or flywheel.
See the image example shown below of how and where to apply grease:
Never wash the release bearing in cleaning solvent. Because cleaning solvent will remove the lubricant from the bearing and cause premature failure.
Make sure the hub of bearing and transmission's front bearing retainer should be free of all imperfections and hard spots.
If the bearing retainer has any defects, it should be replaced.
During the installation of a release bearing, ensure that its retaining clips are safely in its actual position.
See the image below showing release bearing retainer clips:
On vehicles with a concentric slave cylinder, the release bearing is part of that assembly. The release bearing and the clutch slave cylinder can be individually replaced.
See below how disassembly and assembly is done on that vehicle models:-----
Please Note:-- The release bearing is held to the cylinder by a retaining ring.And that has to be removed to free release bearing.
" What Is Clutch Fork."
A very important part which helps for the working of clutch pedal.Clutch fork transfers motions through the clutch pedal release mechanism and linkage to the throw out bearing and pressure plate. The fork forces the release bearing in opposition to the diaphragm spring, shifting the pressure plate backside and releasing the pressure plate from the clutch disc.And this is how it operates.Image of Clutch Fork:
Clutch fork is operated by clutch cable.
Know About Clutch Cable:
"Clutch Cable"
On manual transmission if clutch seems loose and not performing right,the issue can be related clutch cable.The cable also gets over stretched by age and looses its holding tension.Inspect the clutch cable for binding, fraying and corrosion.If it looks very old and forming cracks,then replace the clutch cable.
See below the image showing manual transmission clutch cable:
If the cable seems ok,but looks bit misaligned or dried and dirty then it can be serviced and used instead of replacing it.
"How To Service Clutch Cable."
By performance wise clutch linkage can perform the same controlling action as clutch cable. Clutch linkage mechanism does it with the shaft and lever linkage but with fewer parts. The clutch cable system does not take up much space. Additionally, it has the advantage of flexible installing so it can be routed to the power brake and steering units. These advantages make it the most frequently used clutch linkage.A basic layout image diagram of Clutch cable system :
On a clutch cable oriented automobile vehicles cable adjustment is made by adjusting the length of the outside of the cable housing.
See below image showing how to adjust clutch cable through adjusting nut:
The cable is adjusted for the correct movement of clutch pedal free-play.
On linkage type clutch mechanism the adjustment is similar to the threaded rod clutch system.Linkage type clutch system is also known as mechanical clutch system.
See below the image shows how to adjust clutch system on mechanical clutch system:
And the third type of clutch system is the latest type,which latest car models have,that is Hydraulic clutch systems.This are automatic clutch systems.
Hydraulic systems tend to be self adjusting and have a full-time contact release bearing. For the hydraulic systems that require adjustment, there is an adjustment lever/bolt provided on the slave cylinder pushrod.
"Clutch Pilot Bearing"
The bearing at the output end of the engine's crankshaft that supports the transmissions input shaft is clutch pilot bearing/ pilot bushing.Look below image of clutch bearing:
"Clutch Pilot Tool"
Clutch pilot tool is a important tool to adjust clutch pilot bearing and centering its position.Its a very hard tough plastic, custom-designed tool that simulates the transmission input shaft. Needed to centralize and ensure proper clutch disc alignment during installation.
It can be easily available at local auto parts store.
See below the tool:
"Clutch Master Cylinder"
Clutch Master cylinder is hydraulic clutch-system component having an crucial reservoir tank filled up with brake fluid where pressure is created when the driver utilize the clutch pedal. This causes linkage movement on a position in the clutch slave cylinder and engaging the clutch.The working process of Hydraulic system on clutch linkage is similar to the hydraulic brake operation. The pressure is created by brake fluid in the reservoir tank.Liquids cannot be condensed, so they can transfer motion and maximize torque.
The input piston is positioned in the master cylinder (action cylinder) linked to the clutch pedal.
See below basic working movement of hydraulic clutch master cylinder:
When hydraulic operated clutch system goes faulty problems like slipping clutch,partial engagement in clutch,clutch disengagement issues are noticed:
How to inspect and troubleshoot those issues,this will also be discussed below.
First understand more about clutch master cylinder and its working operation.
Hydraulic operated clutch is located next to brake master cylinder.
Output piston is located in slave cylinder.Slave cylinder is also called as actuator cylinder.The piston is located exactly to the release lever at the clutch.Both cylinder master cylinder and slave cylinder are hydraulically attached by tubes and hoses.On most of custom vehicles hydraulic systems are used due to its easy assembly and modification.
The output piston is located in the reaction or actuator cylinder, commonly called a slave cylinder. It is attached to the release lever at the clutch. The two cylinders are attached hydraulically by tubing and hose, just like in the brake system. Hydraulic systems are popular on custom vehicles because adaptation of the clutch release mechanism is easy.
Big difference in both clutch master cylinder and a single brake master cylinder is the brake master cylinder has a extra check valve for drum brakes. A clutch master cylinder has no such valve for the reason that the clutch would remain applied like a foot always resting on the pedal. And this results in failure of a standard release bearing.
Also you can first visually inspect the hydraulic clutch system before directly going for dis-assembly and replacing components.
First check the fluid level,if its low,you know it has to be filled.Make sure you use good quality brake fluid.If you have recently filled the fluid and it shows low in few days,then you know there is a hydraulic fluid leak.
As its fact that clutch master cylinder will not use up fluid, check for leaks in the master cylinder, connecting flexible line, and slave cylinder, if the fluid is low.
A problems like
"Pulsating Pedal" is caused due to internal failure in clutch.To confirm clutch has to be taken apart.
"Spongy Pedal" is caused due to air in line.The air has to be bleed from the system.
"Slipping Clutch Pedal" has many possible reasons.But you can test it.Shift the vehicle to its highest gear range.Now set the parking brake and make the vehicle move.If the RPM rise clutch is slipping.If the clutch is hard to move the engine will die.
"Partial Clutch Engagement" is common reason for slipping clutch.Clutch free-play gets hard and clutch disc wears on manual transmission clutch operating system.
A small wear or damage defect to clutch disc can cause effect on clutch free-play movement.If more damage is caused,later on clutch slipping is noticed.So as soon as you notice bit of clutch movement issue,get the clutch system inspected for its damage.As soon as the clutch disc gets misaligned and worn the internal temperature of the clutch system increases and that results in burns and overheating inside to clutch components pressure plate.
"Partial clutch Disengagement" is noticed on hydraulic operated clutch systems.Low fluid level is main cause of such problems.Failed master and slave cylinder is another cause.Inspect the leaking parts and replace as necessary.
The leaks are mostly noticed at hoses and joints.Brake master cylinder will be noticed at passenger compartment,so inspect for any leak at floor mat where the foot rests.
Other possibility can be internal master cylinder leak.There is simple procedure to confirm the leak.
Just pump the clutch pedal and hold it to the floor while starting the engine. If the clutch slowly begins to engage, there is an internal leak.So master cylinder has to be replaced,the procedure is explained below .
There are two rubber cup seals in master cylinder assembly which mostly fails.
One is primary cup and secondary cup.
See below how the master cylinder internal assembly looks:
"How To Replace Master Cylinder"
Clutch Master cylinder located next to brake master cylinder.Next comes slave cylinder attached to the release lever at the clutch.This two cylinder are attached together hydraulically by tubes and hoses.
Now to remove the master cylinder first remove the reservoir tank cover and remove the fluid from the reservoir.Next remove the wiring connector attached to the master cylinder.Then remove the hoses and tubes,next remove the attaching bolts which holds the master cylinder. Then remove the master cylinder.After that disconnect pushrod from the pedal.Once the push rod is out,master cylinder is free from assembly to replace.
Before re-installing master cylinder,its advisable to flush the master cylinder with brake fluid.
"How to Flush Master Cylinder"
To flush master cylinder fill up the reservoirs tank and the cylinder bores about one-third total with clean brake fluid, mount the reservoir cover, connect the line ports, shake the cylinder to pass on the fluid all over, and drain out all the fluid.
Now Master Cylinder Replacing process:
First bleed the cylinder.With new master cylinder also replace old hub and seal .Place the master cylinder in its actual position,same as you removed the old one.Please mark the position of old master cylider before removal,this helps while assembly.
Tighten the bolts to secure the master cylinder body.
Reconnect pushrod and pedal.
Now its time to fill up the brake fluid in the master cylinder tank.
"How to Fill Master Cylinder Reservoir"
Remove the bleeder tube from outlet connecting port connecting the fluid line.Do not tighten the fluid line.Place dry cotton cloth to hold the leaking fluid if any.
Fill the reservoir to 3/4th of its actual level.And then push the brake pedal slowly,this with let the brake fluid to enter the reservoir.You will notice some air bubbles forming,you have to follow this procedure till clear fluid gets in and no air bubbles noticed.Now its time to tighten the fluid line with pedal pressed in and no air bubbles seen.
Fill the reservoir to correct level without overfilling it.And then replace the cover and reconnect all disconnected wires.
Test the pedal movement and adjust its free-play as necessary.
Make sure pedal is not very tight to push and not very loose to come up.If brake pedal seem over tight and very loose then its sure that you have not followed the procedure right.On some cases the procedure has to be followed few times to make the fluid fill right.
"What Comes With New Clutch assembly"
Clutch replacement kit includes: cover assembly or pressure plate, clutch disc, throwout bearing and alignment tool.
"How Exactly To Replace Clutch assembly"
First its advisable to inspect the clutch assembly.If the problem is confirmed,then clutch assembly has to be replaced.Clutch assembly inspection procedure is explained in detail in the above section.
Now to replace clutch assembly,first get few color markers to note down the exact position of actual clutch assembly.Do not remove the clutch assembly without marking its position.Because while re-assembly it will confuse you.
Mark exact position of clutch cover,flywheel plate and other clutch system components.
Please make sure you make use an aligning arbor to hold the disc while removing the clutch cover.
See below the image showing how to use the aligning arbor
Once the clutch cover is out,remove the bolts holding pressure plate.Once the bolts are out the clutch system parts will be easy to fall,the components are heavy so make sure you take proper care and place it in safe lace.
Now clean the internal clutch part with brake system cleaner and lubricate the parts which needs grease.
Dirt and rust collected on metal surface can be deglazed with use of sandpaper.
One more important note,please make sure you don't use important solvent time liquids to clean the clutch components,this solvents contain oil particles which are not suitable for the cleaning and will cause clutch slippage and clutch warpage issues.
Its always not necessary that new clutch assembly parts are required due to clutch problem,just inspect the condition of clutch disc ,if it seems worn out and very old then only clutch assembly has to be replaced.But if clutch disc looks good then same disc can be reused.
Also make sure the condition of pressure plate is not bad or rough,it should be smooth and flat.
To replace the clutch assembly:
Install the clutch cover.
Install the clutch disc.
Attach the disc and clutch cover to the flywheel.
Align the punch marks on the flywheel and clutch cover if the parts are being reused.
Align the clutch disc.
Then test the working of clutch system to confirm the clutch is operating fine and working good.
"Regarding Auto Parts"
Please make sure you go for branded part,because the performance of branded part is much better as compared to after market parts.Aftermarket parts are not bad parts,but they quality and material is not of very high quality.Also they dont last long and sometimes fitting issues are also noticed.
I hope this clutch and clutch problem details will very much help you to know and understand the vehicles clutch system and solve the clutch problems noticed on vehicle.
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