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Old 29th March 2010, 12:58   #1
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Default Hydraulic Clutches - Why the hardness, even when condition is good

At around 20K, the clutch of my safari, a hydraulic clutch became very hard, with pressure meter reading around 18(16 is the limit for replacement).
So clutch was replaced under warranty, and upon inspection the old clutch plates and pressure plates were found to be in perfect condition.
At that time the clutch pressure was 9
Now the safari's done 40K+ and the clutch is definitely harder than when it was new.
There is no slippage, no other issues, and I am sure the plates are fine.
But the clutch is hard.
Infact, I have seen that in all vehicles, whether scorpio/safari or any other hydraulic clutch equipped vehicle, after few thousand kms, the clutch gets much harder than what it was new.
Why so?
What is the cause of clutch hardness?
Is it air in fluid? If so bleeding should fix it, but it does not. Note that I am talking about clutches which have done only a few thousand kms and have not been abused at all(plates etc., are fine).
So whats the "thing" here which causes a clutch to be hard?
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Old 29th March 2010, 13:06   #2
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I have the same problem, the clutch of my Palio has become very hard over the years, now the car has run 50K. I recently had its MC replaced and I hoped that it will make the clutch a bit soft, but it is still the same. In fact, the clutch was harder immediately after the MC replacement, and now after a couple of thousands of Kms, it has become a bit softer.

I also would like to know the reason.
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Old 29th March 2010, 13:12   #3
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Quote:
Originally Posted by tsk1979 View Post
So whats the "thing" here which causes a clutch to be hard?
My Dad's Palio and bro's Safari had the exact same problem. It was traced to a faulty clutch master/slave cylinder combo. Once replaced the clutch was far better to operate.

It is important to change the brake fluid every 2-3 years for max efficiency. Since you've ruled out an air bubble, the other issue that can cause this is contaminants in the hydraulic line.

Either way a system flush and refill combined with an inspection of the hydraulic actuation system (clutch master/slave cylinder + hoses and pipes, the reservoir and fluid is generally common with the brake system) should help diagnose and fix the issue.

Cheers!
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Old 29th March 2010, 13:13   #4
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The clutch in my GTX is still hard after bleeding / brake & clutch oil change. I did not feel any difference after the oil change.

i drove one 1.2 at the service centre (a year back) with about 35K on the odo and it had a hard clutch.

it is a major pain to adjust to the clutch/brake in the Getz (9K) immediately after driving the Palio.
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Old 29th March 2010, 14:54   #5
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Post Hard clutch problems

Quote:
Originally Posted by tsk1979 View Post
At around 20K, the clutch of my safari, a hydraulic clutch became very hard, with pressure meter reading around 18(16 is the limit for replacement).
Infact, I have seen that in all vehicles, whether scorpio/safari or any other hydraulic clutch equipped vehicle, after few thousand kms, the clutch gets much harder than what it was new.
Why so?
What is the cause of clutch hardness?
Is it air in fluid? If so bleeding should fix it, but it does not. Note that I am talking about clutches which have done only a few thousand kms and have not been abused at all(plates etc., are fine).
So whats the "thing" here which causes a clutch to be hard?
What is the pressure unit that you are mentioning here? Clutch becomes harder and free play reduces as the release bearing has moved forward from its position thus resulting in higher pedal effort (gear shifting may also be a bit notchy). This is the reason why clutch pedal free-play is measured and adjusted during service intervals. Air inside the lines will make the pedal soft and mushy resulting in a "spongy" feel.

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

How to diagnose clutch related problems?

Drive the vehicle in normal operating speeds, shift to all possible gears and observe the behavior of clutch/clutch action, pedal feel etc. If chatter, grab, slip or improper release is experienced then only inspect clutch assembly. Else if the problem is noise or hard shifting then the likely problem is not clutch, it may be transmission or driveline. How come? Read on.

Clutch misalignment-
Clutch, flywheel and the pressure plates have to be aligned with the crankshaft and the transmission input shaft. Misalignment caused by run outs/warpage will cause clutch to grab/judder as well as improper release resulting in hard gear shifting. Flywheel run-out needs to be checked whenever misalignment is suspected, for flywheel run-out stick to manufacturers recommendations (i am attaching a pic for further clarification). Some of the common reasons for excessive run-out are- a) Improper machining b) Incorrect bolt tightening c)Warpage due to heat d) Foreign material entry etc

Moreover, the misalignment of clutch housing can also be due to
a) Incorrect seating on the engine/transmission b)Loose or missing mounting bolts c) Missing dowel locators d) Non parallel mounting surfaces.

Absence of this alignment can be judged by uneven wear of the diaphragm and release bearing.

Note- To check for clutch housing misalignment bell housing run-out also needs to be checked. Hope this clarifies.

Spike

P.S. Hard gear shifts can also be due to:-

a) Contaminated clutch fluid in lines b) Incorrect pedal free play adjustment.
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Last edited by SPIKE ARRESTOR : 29th March 2010 at 14:57.
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Old 29th March 2010, 15:47   #6
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Hi Spike, I was refering to a meter which they attach on the clutch pedal. Then they press the clutch and measure hardness.
Here there is no gear shifting involved. I was just talking about the effort needed to depress the clutch pedal. Why does it increase over time
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Old 29th March 2010, 16:33   #7
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Quote:
Originally Posted by SPIKE ARRESTOR View Post
Spike
P.S. Hard gear shifts can also be due to:-
a) Contaminated clutch fluid in lines b) Incorrect pedal free play adjustment.
What is the relevance of this picture in clutch pedal being hard to press?
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Old 29th March 2010, 17:44   #8
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"A 'hard' clutch is also a common problem. All clutches require some amount of force to depress fully. If you have to press hard on the pedal, there may be something wrong. Sticking or binding in the pedal linkage, cable, cross shaft, or pivot ball are common causes. Sometimes a blockage or worn seals in the hydraulic system can also cause a hard clutch." - Source How Stuff Works

@

HowStuffWorks "Common Problems and Other Types of Clutches"
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Old 29th March 2010, 18:00   #9
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hi, sorry to go slightly OT, but i have a different issue with the clutch on my Lancer. It's not hard at all but after about 15 minutes of driving, the clutch pedal starts making strange 'crunchy - squeaky' sounds when i engage the clutch. Every time i press the pedal, there's this strange noise and feel - a bit like compressing a bad spring.
Any ideas what the problem might be?
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Old 29th March 2010, 18:09   #10
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@jerry, It seems that your clutch release bearing is going bad.

Slightly OT - but I have noticed that even a non hydraulic clutch is really soft when its brand new and gets hard after the first few days. Why does that happen - is it simply because the lubrication in the moving parts dries up?
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Old 29th March 2010, 19:34   #11
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Quote:
Originally Posted by tsk1979 View Post
Hi Spike, I was refering to a meter which they attach on the clutch pedal. Then they press the clutch and measure hardness.
This instrument is called as pedal effort gauge, the figures you have mentioned is the pedal effort in kgs/kgf which the driver experiences while engaging/disengaging clutch. The pedal effort Vs pedal travel curve follows a hysteresis graph. For measuring this first the pedal freeplay needs to be set. Clutch becoming hard after sometime (free play reducing) is due to the throwout bearing moving closer to the clutch assembly, this happens with time and needs to be set at periodic intervals. Every clutch is designed for a clamping load at which the diaphragm springs come into action, although axial thrust must remain the same two conditions occur during the cycle of a clutch- a) Uniform pressure when the clutch is new b) Uniform wear when the clutch becomes old, this leads to a variation in pedal effort.

Quote:
Originally Posted by clevermax View Post
What is the relevance of this picture in clutch pedal being hard to press?
Dude, a hard clutch can also be a result of misalignment between flywheel-clutch-transmission input shaft.

Quote:
Originally Posted by jerry can View Post
It's not hard at all but after about 15 minutes of driving, the clutch pedal starts making strange 'crunchy - squeaky' sounds when i engage the clutch. Every time i press the pedal, there's this strange noise and feel - a bit like compressing a bad spring.
Any ideas what the problem might be?
Does this noise come everytime you press the pedal or only sometimes? Have you checked the suspended pedal assembly? Also check if the sound is coming from the release bearing.


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Old 29th March 2010, 20:37   #12
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As for the suinchy sound, I would suggest that you look at the spring. Its a simple cheap part, and known to go bad often
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Old 29th March 2010, 21:17   #13
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Quote:
Originally Posted by tsk1979 View Post
Note that I am talking about clutches which have done only a few thousand kms and have not been abused at all(plates etc., are fine).
So whats the "thing" here which causes a clutch to be hard?
Hey did you try greasing and lubeing all the joints in the clutch pedal. That and the seals in the MC/SC are the only 2 things I can think of.
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Old 30th March 2010, 00:30   #14
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Thanks for your quick responses guys..
@spike - the pedal is totally smooth and silent the first 15 min or so when the engine is cold, but once i've driven for a while the sound and scrunchy feel is there every time i press the pedal.
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Old 30th March 2010, 01:04   #15
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Ditto is the condition of my 35k driven innova no slippage clutch strong but very hard ! Driving in traffic is a nightmare tried bleeding did nt help at all was adviced so but yet went ahead with it no result although ! Service advisor says sir your call if you wanna replace it !!! Please advice
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