Author Topic: Low clutch bite point resolution  (Read 2699 times)

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  • nz New Zealand
    Auckland, NZ
  • 2008 1.6 cRDi manual Elite in Stone Black
Low clutch bite point resolution
« October 10, 2016, 22:17:34 »
Hi All,

About a year ago when my FD 1.6 diesel i30 was at around 200,00km, the clutch bite point suddenly changed. Previously it was at around half of the available pedal stroke and suddenly was at about 30mm from the floor.
After a week or so, I took the car to my local mechanic who said the clutch was fine … ‘no issues at all’. I carried on driving. Sometimes the bite point seemed to improve a little. Although the next morning when the car was cold, it was back to being quite low.

Searching the i30 forum indicated a few have experienced something similar, sometime being resolved by bleeding the clutch, sometimes not. After putting up with a low bite point for about 8 months and 35,000 km, I took the car into the previously mentioned local mechanic for a complete clutch fluid change (and complete bleed). And afterwards … it was still the same 
Again, I left it for a while. Was getting quite good a double de-clucthing by this stage.  Eventually though, I decided this needed fixing. Off to a clutch specialist. He said the hydraulic system was the place to start as the cheapest. Noticed a weeping clutch slave cylinder. That was rebuilt, the system bled again and I picked it up expecting a vastly improved bite point. Nope, just the same. The master cylinder ‘looked OK’ according to the clutch specialists. But I decided to rebuild the master clutch cylinder (none available new in NZ and quite expensive anyway).

I decided to buy a second hand cylinder and have that rebuilt as then it was simply a swap over and bleed. Had a look at the master clutch cylinder and noticed it looked a little different to what I expected.



The cylinder appeared like a regular cylinder but then it went into another odd shaped device (the rusty piece in the photo). Bit of research needed here. The ‘extra’ piece is in fact a ‘clutch damper’. My research shows that this damper appears exactly the same as the one used on many models of Subaru. Its function is to slow down the clutch engagement. Initially installed in 2003 on Subaru WRXs after many customers in the US (or so the story goes) destroyed gearboxes by engaging the clutch too quickly. A diaphragm in the damper effectively puts a buffer between the clutch pedal and clutch release arm in the gearbox resulting in an engagement delay. Quite interesting as even from new, I noticed when I really wanted to go quickly (lots of revs, release clutch pedal quickly), the clutch appeared to slip for a second. I assumed it was my poor driving.

Anyway, the delayed clutch engagement is not an uncommon feature in cars these days and many do it. BMW use something they call a ‘CDV’ (clutch delay valve). Earlier Hyundais (up to 2007) used a valve in the clutch slave cylinder to do the same thing – full fluid flow when pushing down the clutch pedal and reduced flow when released.

Do these ‘dampers’ have any negative features? This is where it gets interesting. Just type ‘Subaru clutch damper delete’ into GOOGLE and read away to your hearts content. I read they can cause (especially when the diaphragm in them splits):

•   Disconnected clutch feel (whatever that means)
•   Variable bite point
•   Low bite point

Hmm, wonder if I could delete it. Asked the clutch place. Yes, they had deleted them on Subaru’s by sleeving the cylinder and not drilling the orifice through to the damper. But my i30 cylinder was different than the Subaru setup. The damper was separate from the cylinder. Looking at it, I figured it unscrewed. And so it did with a copper washer to seal it. I decided I could replace it with a bolt  with a copper washer. Measuring up the damper thread, it is M16x1.50. Figured a sump plug would possibly do the trick and GOOGLE told me some Volvo or BMW sump plugs would work. The local parts store had them by size which was even easier. I purchased an M16x1.50 sump plug which had the same thread length as the damper – how handy.








The clutch place rebuilt the cylinder, installed the sump plug in place of the damper, reassembled and bled.
So any improvement in the clutch bite point? Yes, the clutch bite point is back to where it was – half way up the pedal travel.
Reading up the effects of removing a damper it was interesting how it was on the i30. Common claims are:

•   Improved bite point (previously low, sometimes variable) … YES
•   Firmer pedal feel … NO, feels just like before
•   More direct clutch engagement … YES, let the clutch pedal out quickly and you can feel it bite, normal driving not noticeable (I have had 36 cars, all of them manuals over 40 years – have never owned an automatic). No engagement delay at all when I want to really take off quickly – just grabs and goes.
•   More direct pedal feel … MAYBE, sometimes I think I can feel some vibration in the pedal. Maybe that is the engine vibration through the clutch arm, through the hydraulic system into the clutch pedal. Possibly not as smooth as before but still a very easy clutch to use.

The big question is, was it the deletion of damper that solved this issue for me or the rebuilding of the master cylinder? The answer is that I don’t know. I could replace the bolt with the damper, re-bleed and try. And if I am back to a low bite point, can assume there is an issue with the damper  (because for 200,00 km it was fine) and replace the damper. Are they even available as a spare part?
Am I going to?  No, am pretty happy with how it is. I feel I do not need a clutch aid to use a clutch.

DISCLAIMER: I have to put this in. What I have done has worked for me. Some ‘experts’ on forums have suggested what I have done puts more strain on the clutch system and can lead to failure of parts. I can obviously offer no guarantee that if you have a low clutch bit point that this is the issue. And in the same vein, I cannot guarantee that if you do this you will not destroy your clutch completely. This post is provided by me for your  interest only.

Andrew
« Last Edit: October 11, 2016, 19:45:39 by stkman » »


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Re: Low clutch bite point resolution
« Reply #1 : October 11, 2016, 00:07:47 »
Thanks Andrew.  Excellent post.
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Re: Low clutch bite point resolution
« Reply #2 : October 11, 2016, 00:42:42 »
Thanks Andrew.  Excellent post.

 :whsaid:

We must me same vintage I have been driving for 40 years and had a similar number of cars. I have had about half a dozen Autos/CVT including a work vehicle or two, but was a manual only man for about 30 years... :cool:
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Re: Low clutch bite point resolution
« Reply #3 : October 11, 2016, 03:34:27 »
Awesome!  Thanks for such a comprehensive post :goodjob:

I think we'll put this in our Modifying section :D
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Re: 摇摇欲坠
« Reply #4 : October 11, 2016, 04:05:14 »
Funny, you're a shambles in any language. :lol:
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Re: 摇摇欲坠
« Reply #5 : October 11, 2016, 04:11:24 »
Funny, you're a shambles in any language. :lol:
But in Chinese he's Crumbling :)

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Re: Low clutch bite point resolution
« Reply #6 : October 11, 2016, 04:16:45 »
Thanks for the very informative post, Andrew!

 :goodjob2:

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Re: Low clutch bite point resolution
« Reply #7 : October 12, 2016, 00:56:10 »
Hi Andrew,
Just curious here...how long have you been driving your i30 without the damper installed?

Cheers,
Paolo

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  • nz New Zealand
    Auckland, NZ
  • 2008 1.6 cRDi manual Elite in Stone Black
Re: Low clutch bite point resolution
« Reply #8 : October 12, 2016, 15:15:10 »
Hi Paolo,

Has been about 2 weeks (~1500 km) since the rebuilt cylinder without the damper was installed.

Great to have a stable bite point. Most of the time just like it was for the first 200,000km ... a nice clutch. Even better when I need to get going quickly. Clutch just bites. Nice.

270,000 km on the original clutch and works fine  :D
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