[clevermax]

Originally Posted by SPIKE ARRESTOR

Dude, a hard clutch can also be a result of misalignment between flywheel-clutch-transmission input shaft.

Well, here in my specific case, the hydraulic clutch pedal is hard to press and I don't think it is due to a misalignment between whatever you have mentioned. In fact, I don't think this could be the reason of hard clutch pedal for any of us who have posted here saying their hydraulic clutch pedal is hard to press. And, didn't get the point of LOL smiley.

I believe your problem is hard gear shifting related to clutch and not hard shifting effort in transmission.

Actually Tanveer asked about reasons why clutch pedal becomes hard to press. He didn't even write one word about gear shifting.

P.S. Hard gear shifts can also be due to:-
a) Contaminated clutch fluid in lines

Won't the hard clutch pedal be the first and most obvious thing to note when there is contamination in the fluid? It may result in a hard shifting. I wonder why the topic of hard shifting came into picture.

[SPIKE ARRESTOR]

Originally Posted by clevermax

In fact, I don't think this could be the reason of hard clutch pedal for any of us who have posted here saying their hydraulic clutch pedal is hard to press. And, didn't get the point of LOL smiley.
It may result in a hard shifting. I wonder why the topic of hard shifting came into picture.

Dude, leave the smiley part, you have not understood the other things which i was trying to say. With my limited knowledge, i know Hard shifting can mean two things- Your clutch is hard or your shift lever is hard. You/others may not agree with the misalignment stuff as you have never experienced it, luckily for me i have seen such cases.

Spike

[tsk1979]

I was actually talking about clutch pedal hardness. No shifter has come into play yet.
For example, on a brand new safari/or new clutch, when you press clutch in neutral the effort needed is around 9 units on the pressure meter(I do not know what unit it measures),
However, on most safaris done 5000kms or more, the effort is close to 13-14 on the meter.
What is it which causes the clutch to go hard with use after few thousand kms of usage. Surely it cannot be a defect in all the vehicles?

[SPIKE ARRESTOR]

Originally Posted by tsk1979

What is it which causes the clutch to go hard with use after few thousand kms of usage. Surely it cannot be a defect in all the vehicles?

Tanvir, you are right, i agree with you on this, all vehicles cannot be defective. I have answered your question in my earlier post (Post #11), the diaphragm spring also has a defined life cycle, after which they start loosing their material properties (just compare the diaphragm spring of a fresh pressure plate and that of a worn out one you will understand), this results into a change in clamping load which is felt by the driver through the pressure plate->release bearing->fork->clutch pedal. I hope this clarifies.

Spike

[dadu]

Its because of the hydraulics (I guess we all know that), primarily the Slave cylinder is the culprit, so bleed or a replacement will make it soft without changing the clutch assembly under low run conditions like tanveers.

Ask them to bleed it first

then change only the slave cylinder, mostly it will go soft.

otherwise Clutch assembly needs a change.

[clevermax]

Originally Posted by SPIKE ARRESTOR

Dude, leave the smiley part, you have not understood the other things which i was trying to say.

That's not rocket science you explained there, or is it? Most people around here including me can understand it well. What I said was, that's probably NOT the likely cause here for the hydraulic clutch pedals becoming hard to press, and I am very sure on that.

I'd prefer to be called by my name or if you don't know my name, at least use the t-bhp handle or don't use any name at all, but please, no 'dude'.

[SPIKE ARRESTOR]

Originally Posted by clevermax

That's not rocket science you explained there, or is it? Most people around here including me can understand it well. What I said was, that's probably NOT the likely cause here for the hydraulic clutch pedals becoming hard to press, and I am very sure on that.

I'd prefer to be called by my name or if you don't know my name, at least use the t-bhp handle or don't use any name at all, but please, no 'dude'.

I agree it is not rocket science, also if it is not rocket science why don't you explain us what is the actual cause?. What i had tried to explain was my experience with a similar case study on clutches.

The beauty of the word "probable" is, it is only a prediction, or an educated guess, it need not be correct. What i mentioned in my previous post was not just for the educated lot but also for novices who want to learn a few things (all students in a classroom are not equal).

Clevermax, i am sorry for addressing you as "dude".

Spike

P.S. Just for your information I happen to see at least 1000 transmissions being assembled and fitted everyday (in 8 hours), and it is only after our approval they see the light of day

[tsk1979]

Okay guys, lets get back to topic.
SPIKE, can you put down a summary post detailing the possible causes of "Hard Clutch" after use.
i.e. after the vehicle runs a few thousand kms, the effort needed to depress clutch peal increases.
Also put some points as to why in some cars, the effort to depress the hydraulic clutch becomes very high. inspite of plates being fine.

[SPIKE ARRESTOR]

Originally Posted by tsk1979

Okay guys, lets get back to topic.
SPIKE, can you put down a summary post detailing the possible causes of "Hard Clutch" after use.
i.e. after the vehicle runs a few thousand kms, the effort needed to depress clutch peal increases.
Also put some points as to why in some cars, the effort to depress the hydraulic clutch becomes very high. inspite of plates being fine.

Hi Tanveer, I will try to summarize the reasons/possible causes for "Hard Clutch" in automobiles:-

1. Clutch fluid less or contaminated- As you know this fluid DOT3/DOT4 is hygroscopic, it may attract moisture and become useless after sometime/no use. This contamination may be due to leaks in the system or the strainer missing from the clutch master cylinder reservoir.

2. Incorrect Clutch Pedal free play- The release/throwout bearing of the clutch system is designed to move a defined distance, as a thumb rule it is approximately 8.5 mm in axial direction (X axis), out of this 8.5 mm 1.5 mm movement of the release bearing comes from the free play movement from the pedal, remaining 7 mm required for actual engagement/disengagement of clutch is obtained through the remaining movement of the clutch pedal. Although the axial movement must remain the same the motion of the release bearing can either become 3 mm O mm or -1.5 mm (this signifies your free play has changed and needs to be adjusted) due to various manufacturing reasons. Suppose, this movement becomes 0, what does that mean? This means that the release bearing has already moved the 1.5 mm distance which it was supposed to move when the pedal is depressed and hence there is no free play resulting in a feeling of hard clutch.

I owe this explanation to DB Sir, who first explained this to me when I was a trainee 3 years back.

3. Clutch plate warpage- This warpage may be due to misalignment of clutch during handling/manufacturing, clutch replacement is the only option for this.

However, if the clutch is OK when inspected visually and still it feels hard then it may also be due to a defective diaphragm spring. Like i said earlier, they are designed for a life cycle and they loose their properties after some period of time becoming a bit hard. If you notice closely (pic attached) the area where the release bearing contacts the diaphragm spring is heat treated, as time passes by the properties gained by the material is gradually lost making them a bit harder, hence resulting in what we call "Hard Clutch".

Hope this clarifies. Phew!

Spike

P.S. Whatever I have mentioned here is with my limited knowledge / experience and understanding of the "Automobile". Experts, gurus, others can join in with their comments and please do correct me if I am wrong.

[tsk1979]

Thanks SPIKE for the detailed explanation
At the 45 K service I will ask them to check for
1. Contaminated fluid
2. Free play. - I am a but confused about this. Does free play mean that when I start depressing clutch, for some distance, clutch will not get engaged, and only after half press or so clutch starts to engage? I my case, the moment I press the clutch pedal, infact even when I have moved the pedal down only a couple of mm, I start feeling some vibrations through my foot. what could this be?
3. Clutch plate inspection.

[DHABHAR.BEHRAM]

Dear all - hard clutch is the resultant of wear of clutch plate friction material as normal life progresses.The worn material becomes powder which remains in the bell housing and clogs the pressure plate mechanism. Clean everything and put it all back, then see what happens.

In clutch having higher FOS (factor of safety), this phenomenon is under control to a limited extent.

Best regards,

Behram Dhabhar

[tsk1979]

Thanks for the info. Normally, when you take a safari or a scorpio like vehicle with hydraulic clutch, whats the life timeframe as compared to cars.
For example, the clutch on my indica lasted 100,000kms, with similar driving, how long do the clutches of these behemoths last?

[Rahulk76]

Originally Posted by DHABHAR.BEHRAM

Dear all - hard clutch is the resultant of wear of clutch plate friction material as normal life progresses.The worn material becomes powder which remains in the bell housing and clogs the pressure plate mechanism. Clean everything and put it all back, then see what happens.

In clutch having higher FOS (factor of safety), this phenomenon is under control to a limited extent.

Best regards,

Behram Dhabhar

Behram

Is there a easy way to clean it without having TASS guys opening it up and charge $$$$$ for labor rate etc ?

One hard fact of life with TML and TASS for me is that let the sleeping dogs lie..

[DHABHAR.BEHRAM]

Dear Tanveer - life of the clutch is equal to the life of the vehicle. Defined life of a vehicle is 3,50,000 kms. In our test cars, we have achieved this. We run 1000 kms every day, round the clock. There are many causes of low clutch life as we all know.

Dear Rahul - try to blow compressed air through the small slit given at the bottom of the bell housing, keeping the engine in idling speed with the vehicle safely put up on a on a 4 post lift. However, removing and cleaning is the best way. Normally vehicles are sold off by the first owners at such mileage, therefore root cause analysis becomes difficult to control / infer.

Once you know the root cause,corrective action is relatively easy.

Best regards,

Behram Dhabhar

[SPIKE ARRESTOR]

Originally Posted by DHABHAR.BEHRAM

try to blow compressed air through the small slit given at the bottom of the bell housing, keeping the engine in idling speed with the vehicle safely put up on a on a 4 post lift. However, removing and cleaning is the best way. Normally vehicles are sold off by the first owners at such mileage, therefore root cause analysis becomes difficult to control / infer.

While doing this (specially in older cars) be careful that you do not inhale this powder. The clutch facing in older models were known to contain asbestos called as "Ferodo Lining", which under prolonged exposure could cause cancer.

Spike