Benzine
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| posted on 23/12/04 at 05:14 PM |
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M/C Help needed
I recently started work again on my MK as I'm on holiday. I return to the same problem i left off with. I have a problem with the master
cylinder, the braking lines are all setup. When i pumped the pedal nothing seemed to happen. I took off all the brake lines and put my finger over the
holes then applied pressure. The picture below shows what happened:
I felt pressure from the connection to the rear brake line and brake fluid pumps out but nothing at all at the front 2. Could there be air trapped in
it? I remember someone else suggesting that the piston may have not returned after being pumped without brake fluid in it. Any suggestions?
Thanks for any help
Ben
The mental gymnastics a landlord will employ to justify immoral actions is clinically fascinating. Just because something is legal doesn't make
it moral.
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mookaloid
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| posted on 23/12/04 at 06:20 PM |
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Has it been stripped down at all?
I remember stripping one down once and I didn't get the little pin under the reservoir rubber seal in the right place relative to the piston -
needless to say it stopped it working properly.
Perhaps this M/C has one too!
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Rob Lane
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| posted on 23/12/04 at 06:28 PM |
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If the cylinder has been pushed down without fluid it will more likely have jammed the second piston.
It's the rubber seal that will be dry and stuck, the spring having been compressed. I did same thing with a new one.
Don't think this will work but apply an air line to faulty outlet and try a bit of air pressure.
You could also try tapping the body with a plastic mallet and listen for 'ping' as spring pushes it back.
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Dick Axtell
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| posted on 23/12/04 at 06:29 PM |
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Mcyl Press Prob
Hi Ben,
Just to clarify terminology -
The rear outlet port, (nearest the mounting flange), is the Primary port;
The forward outlet port, (furthest from the flange), is the secondary port.
From your message, and the pic, it seems that you can produce pressure from the primary port, but not the seocndary port. Correct?
Now, is that a Sierra mcyl? It appears to be, from your pic. If so, then it is a "simultaneous cut-off" type. Inside, there is a primary
spring attached to the primary piston, by a small telescopic retaining assembly, which predetermines the fitted length and load of that spring.
The secondary piston is fitted with a simple return spring, which has a fitted load sufficient to return BOTH piston assemblies. So, if your primary
piston returns fully, with no line pressure applied, then the secondary piston must also return to its "back-stop" position.
I suggest you carry out a more searching bench test. Fill the mcyl with brake fluid, and fix up a pressure gauge to each port, in turn. Blank off the
port not being checked, with a bleed screw. Then you should be able to verify the degree of pressure generated for each mcyl chamber.
Good luck!
Work-in-Progress: Changed to Zetec + T9. Still trying!!
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Dick Axtell
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| posted on 23/12/04 at 07:50 PM |
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quote:
Originally posted by Rob Lane
Don't think this will work but apply an air line to faulty outlet and try a bit of air pressure.
But please arrange the open end of mcyl against flat surface - just in case pistons are blasted out!!!
It has happened - that little stop pin (was in secondary inlet) had fallen out!!
Might be a good idea to remove the primary piston assembly first. Keep all internals in a clean container (use meths or IPA).
Let us know if you find out more.
Work-in-Progress: Changed to Zetec + T9. Still trying!!
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Dusty
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| posted on 23/12/04 at 08:18 PM |
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It's often difficult to get brake fluid to flow from the resevoir into the two cylinder chambers and you can be pumping away for ages with
little effect. Helps to use an ezibleed or other pressure or vacuum device to get the initial flow started.
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Benzine
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| posted on 23/12/04 at 09:19 PM |
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Thanks all for responses, I'll be trying suggestions out at first light 
[Edited on 23/12/04 by Benzine]
The mental gymnastics a landlord will employ to justify immoral actions is clinically fascinating. Just because something is legal doesn't make
it moral.
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