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 How to Change Clutch Fluid?
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EdinburghJoe
Starting Member

United Kingdom
24 Posts

Posted - 09 Sep 2017 :  12:05:43 Show Profile Reply with Quote
Hi, I'm wanting to change the fluid in the clutch of my 1973 96 - it is working fine, but the MOT guy said the boiling point was low and it could do with changing. Brakes fortunately OK (190c plus)
I've heard it's fairly easy, but wanted to get my method straight before I start!

My plan is to open the bleed valve into a tube, and get someone to press the clutch pedal, which should expel fluid. Then close the valve, ask them to release the pedal. Then top of the fluid level in the reservoir. Then repeat the process, until a sufficient amount of fluid has been added.

Does this sound right? I know not to let the level in the reservoir drop or I'll introduce air into the system.

How much fluid should I add before I can be sure it's all replaced? I have 2 litres of dot 4.

If what I've said above is rubbish then please correct it- it's based only on part conversations in the past plus theories I've made up!

Thanks,

Joe.

Joshinator99
Starting Member

USA
37 Posts

Posted - 09 Sep 2017 :  13:28:21 Show Profile Visit Joshinator99's Homepage Reply with Quote
I'd say you're on the right track. You're just trying to flush the old fluid through the system using fresh fluid, since the old fluid absorbs moisture over time. The workshop manual doesn't say the fluid capacity of the system, one liter is going to be plenty! The reservoir probably holds half of that, and you're just bleeding the system enough to get the old fluid out.

1972 Sonett III
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melle
V4 Guru

United Kingdom
2283 Posts

Posted - 09 Sep 2017 :  13:44:08 Show Profile Visit melle's Homepage Reply with Quote
I wouldn't be too concerned about the boiling point of clutch fluid. If you insist on changing it, I would use an Eezibleed, much more convenient than having someone pump the pedal. Once clean fluid comes out you're done.

www.saabv4.com
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Derek
V4 Guru

United Kingdom
1782 Posts

Posted - 09 Sep 2017 :  18:57:15 Show Profile Reply with Quote
MOT man testing boiling point of clutch fluid, whatever next!! Much more important to test the brake fluid but I've not seen it done. Rules have got tighter though. As said tube off the slave nipple into a jar with the end under some fluid a couple of pedal pushes. and hold down pedal while someone tops up the pot. Repeat several times and then tighten the nipple with the pedal down. If you are having problems getting fluid through open the nipple more, needs to be open quite a bit but it does have a short thread so be careful.

Get one of these. There are long and short versions of these. This is the longer one and more versatile when doing brakes. Makes the job very easy.

https://www.amazon.co.uk/Pearl-PWN189-Automatic-Brake-Bleed/dp/B00ALTZEQ0/ref=sr_1_fkmr3_3?ie=UTF8&qid=1504983003&sr=8-3-fkmr3&keywords=brake+bleeding+rubber+tube
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Joshinator99
Starting Member

USA
37 Posts

Posted - 10 Sep 2017 :  00:08:28 Show Profile Visit Joshinator99's Homepage Reply with Quote
quote:
Originally posted by melle
I wouldn't be too concerned about the boiling point of clutch fluid. If you insist on changing it, I would use an Eezibleed, much more convenient than having someone pump the pedal. Once clean fluid comes out you're done.

www.saabv4.com



I agree with a melle, boiling point of clutch fluid shouldn't be an issue. New fluid still a good idea though, due to the hydroscopic nature of the fluid.

1972 Sonett III
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EdinburghJoe
Starting Member

United Kingdom
24 Posts

Posted - 11 Sep 2017 :  11:58:53 Show Profile Reply with Quote
I've only had the car for a year - so had no idea when the clutch and brake fluids were last changed. I was talking to the mechanic about this at the last MOT, and he suggested measuring the boiling point as a proxy for age, and replacing if it gets below 180C (because of the increasing water content).

So I tried the method I described above (thanks all for confirming I was kind of on the right track). The fluid didn't drain under gravity, so repeated open valve / depress clutch / close valve / release clutch probably about 50 times, topping up the reservoir as I went, and after that had a jar of about 600ml of pale black fluid.

Job done, but it took ages!

If I was to do it again (and definitely if / when I have to do the brakes) I was thinking of getting a hand operated vacuum bleeder.

The MOT mechanic gave me a tip of NEVER pumping the brake pedal when changing brake fluid on an old car as the master piston doesn't normally travels the full length of the cylinder, and you'd be scraping up all sorts of gunk from the cylinder wall. Clutch isn't a problem as it does travel the full length.

Am I right to think that if I used a vacuum bleeder then I could leave the pedals alone?

Joe
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melle
V4 Guru

United Kingdom
2283 Posts

Posted - 11 Sep 2017 :  12:07:07 Show Profile Visit melle's Homepage Reply with Quote
quote:
Originally posted by EdinburghJoe
If I was to do it again (and definitely if / when I have to do the brakes) I was thinking of getting a hand operated vacuum bleeder.
I use a Gunson Eezibleed system, this uses pressure from a spare tyre and does the job satisfactorily.

quote:
Originally posted by EdinburghJoe
The MOT mechanic gave me a tip of NEVER pumping the brake pedal when changing brake fluid on an old car
He is absolutely right, good tip.

quote:
Originally posted by EdinburghJoe
Am I right to think that if I used a vacuum bleeder then I could leave the pedals alone?
Yes.

www.saabv4.com
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EdinburghJoe
Starting Member

United Kingdom
24 Posts

Posted - 11 Sep 2017 :  13:13:53 Show Profile Reply with Quote
Thanks all for the replies and ideas... Joe.
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