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Joined: Tue Mar 12, 2019 11:16 am
Posts: 10
Vehicle: Sierra SJ70 VX JX Hardtop

Post Posted: Sat Jan 18, 2020 3:11 pm 
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As the title says my Sierra (1994 VX JX Hardtop 2dr 5sp Man 4x4 1.3L) has developed what I assume to be a malfunctioning clutch. The engagement point of the clutch pedal has lowered all of a sudden, and is now close to the floor. Changing from neutral into first and taking off produces a grinding noise. Changing from first to second produces a clunk or two. Changing from 2nd to 3rd and so on seems to sound normal. Each of these gear changes require me to use more force than usual on the gear shifter. Occasionally the clutch pedal 'sticks' making it feel very loose. The cable has been adjusted recently and is at the tightest setting, therefore leading me to question whether the clutch cable has stretched. When the clutch pedal is pressed slightly - before reaching the usual engagement point, I feel a moderate rubbing/grinding. All these problems popped up yesterday. Previously the clutch and gear changes were performing well. Can anyone provide some insight to what they think is happening?
An unrelated symptom (although may be related) is a whining noise, similar to that of a boiling whistling kettle which begins after the engine has been running for a while, and the temperature us up. This sound stops when I use the throttle and the revs increase (in neutral or in gear) and returns as soon as the revs drop back to idle. So I usually hear it when waiting at traffic lights. I am yet to pin point when the sound is coming from, although it seems loudest from the engine bay, and is much louder when standing directly in front of the car.
Any help would be great thanks!

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Joined: Sat Oct 06, 2012 5:49 pm
Posts: 1975
Vehicle: Sierras!! SWB and LWB

Post Posted: Sat Jan 18, 2020 5:15 pm 
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As far as the clutch goes I’d suggest the cable has had itself a mischief. Hard to say for sure without seeing it but if you have a FSM you should be able to check the adjustments and if at its maximum adjustment it isn’t working just fine then replace the cable. I can’t think off the top of my head any reason a clutch failure would produce those symptoms

Noise wise? Process of elimination but I’d be suspicious of things like a alternator bearings, I had a failed one that carried on like a old dry fan belt but was the alternator

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Joined: Thu Feb 26, 2009 10:30 pm
Posts: 13001
Location: Melbourne

Post Posted: Sun Jan 19, 2020 1:35 pm 
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Yes, sounds like a failing/stretched clutch cable.

I'm a little bit confused about the adjustment you spoke of. The only spec for clutch cable adjustment is measured as play at the pedal - there should be 20-30mm of free play in the pedal before you feel any resistance at the pedal. If you've adjusted the clutch to remove this play, it's possible you're bottoming the clutch out which will stretch the cable.

Your noise is most likely failing bearings in the alternator or water pump. With the car up to temperature, loosen or remove the fan belt and start the car. if the noise has disappeared you've narrowed it down. Spinning the water pump or alternator by hand may reveal which it is- it will feel/sound rough.

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Joined: Thu Sep 02, 2010 5:50 am
Posts: 427
Location: Melbourne
Vehicle: '85 Sierra LWB, '99 GV 2.5L

Post Posted: Mon Jan 20, 2020 6:53 pm 
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Clutch cable is the best place to start, as it's the easiest & cheapest bit.
I've had symptoms like that from broken diaphragm spring fingers. Clutch fork throw & the release bearing were fine, but not enough disengagement.
Take off the tin bellhousing cover & see if any bits fall out.
Gearbox out job if it is not the cable.
Rgs, Michael

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