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Dual Circuit Master Cylinder Plumbing
Dual Circuit Master Cylinder Plumbing
by MrPotatoHead » Fri May 04, 2012 12:25 pm
I'm upgrading to dual circuit master cylinder and have a question. There are four outlets three horizontal and one angled down. Clearly one will go to the rears, one is for the switch, and there's one for each front wheel.
The question is, does it matter which one goes where? And if so, what are the differences between them?
I was under the impression it didn't matter and have plumbed the rears to the rear horizontal one, the switch is on the one angled down, and the fronts off the two horizontal front ones. I should have asked earlier but I want to get it right before I roll!
Edit! I should add that it's still drums all round!
The question is, does it matter which one goes where? And if so, what are the differences between them?
I was under the impression it didn't matter and have plumbed the rears to the rear horizontal one, the switch is on the one angled down, and the fronts off the two horizontal front ones. I should have asked earlier but I want to get it right before I roll!
Edit! I should add that it's still drums all round!
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Re: Dual Circuit Master Cylinder Plumbing
by stu(pid) » Fri May 04, 2012 1:44 pm
Try the fitting instructions on this page:
http://www.csp-shop.com/products/Produc ... 4381c/det/
http://www.csp-shop.com/products/Produc ... 4381c/det/
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Re: Dual Circuit Master Cylinder Plumbing
by 58splitty » Fri May 04, 2012 7:40 pm
What youve done sounds right
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Re: Dual Circuit Master Cylinder Plumbing
by Samba63 » Fri May 04, 2012 8:42 pm
Not according to the CSP fitting instructions 58splitty.58splitty wrote:What youve done sounds right
"It is important that the two metal lines that
go to the front wheel are threaded in the
end of the master cylinder farthest away
from the plunger. The rear line and the
switch should go into the holes closest to
the master cylinder push rod."
Front lines to rear of master cylinder - furthest away from the plunger, and not like MrPotatoHead has done.
Rear line to front - nearest the plunger.
Should be round the other way I'm afraid MrPotatoHead!!
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Re: Dual Circuit Master Cylinder Plumbing
by Samba63 » Fri May 04, 2012 8:44 pm
Thanks for that stu(pid)stu(pid) wrote:Try the fitting instructions on this page:
http://www.csp-shop.com/products/Produc ... 4381c/det/
I'll be doing mine soon.
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Re: Dual Circuit Master Cylinder Plumbing
by MrPotatoHead » Sat May 05, 2012 8:23 am
Ah well. Looks like my weekend will be spent replacing/fettleing the brake pipes,
again
Thanks for the replays tho guys, and the CSP instructions. Just wish I'd seen them before!
Still don't know what the difference between the front and back outlets are though. The difference isn't to do with discs is it?
Thanks
Will
Thanks for the replays tho guys, and the CSP instructions. Just wish I'd seen them before!
Still don't know what the difference between the front and back outlets are though. The difference isn't to do with discs is it?
Thanks
Will
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Re: Dual Circuit Master Cylinder Plumbing
by Samba63 » Sat May 05, 2012 10:11 am
Hi Will.
The principle of dual circuit master cylinder operation....
From this link: http://www.autozone.com/autozone/repair ... 52802677d7
Dual circuit master cylinders employ two pistons, located one behind the other, in the same cylinder. The primary piston is actuated directly by mechanical linkage from the brake pedal through the power booster. The secondary piston is actuated by fluid trapped between the two pistons. If a leak develops in front of the secondary piston, it moves forward until it bottoms against the front of the master cylinder, and the fluid trapped between the pistons will operate the rear brakes. If the rear brakes develop a leak, the primary piston will move forward until direct contact with the secondary piston takes place, and it will force the secondary piston to actuate the front brakes. In either case, the brake pedal moves farther when the brakes are applied, and less braking power is available.
When you read it like that it makes quite a lot of sense (to me included)..
Trev
The principle of dual circuit master cylinder operation....
From this link: http://www.autozone.com/autozone/repair ... 52802677d7
Dual circuit master cylinders employ two pistons, located one behind the other, in the same cylinder. The primary piston is actuated directly by mechanical linkage from the brake pedal through the power booster. The secondary piston is actuated by fluid trapped between the two pistons. If a leak develops in front of the secondary piston, it moves forward until it bottoms against the front of the master cylinder, and the fluid trapped between the pistons will operate the rear brakes. If the rear brakes develop a leak, the primary piston will move forward until direct contact with the secondary piston takes place, and it will force the secondary piston to actuate the front brakes. In either case, the brake pedal moves farther when the brakes are applied, and less braking power is available.
When you read it like that it makes quite a lot of sense (to me included)..
Trev
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Re: Dual Circuit Master Cylinder Plumbing
by leeco10 » Mon May 07, 2012 8:48 am
I fitted a dual circuit system from Machine7 and I've got the it the same way as mr potatohead,
I cant find the instuctions now
but it is a different master cylinder from the csp one.
In the manual I've got it shows the rear circuit coming from the rear, and the front brakes coming from the front ports????
Brian.
I cant find the instuctions now
but it is a different master cylinder from the csp one.
In the manual I've got it shows the rear circuit coming from the rear, and the front brakes coming from the front ports????
Brian.
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Re: Dual Circuit Master Cylinder Plumbing
by MrPotatoHead » Tue May 08, 2012 11:36 am
And so the uncertainty continues!
Just for the record, it isn't a CSP Dual Circuit MC that I'm fitting, although I would assume that all available ones would march to the same beat. Mine was from Heritage if my memory serves me correct, or possibly C&C
Another thought though, spoke to a friend over the weekend about this whole "front or back outlets" issue, and he's running as I've done/described above, he's got discs up front, his braking is spot on, and has been for a number of years!
I'm going to bleed the system through tonight, adjust up the shoes/handbrake (as this is the first spin of my new straight axles too!) and give them a whirl. Wish me luck!
Cheers
Will
Just for the record, it isn't a CSP Dual Circuit MC that I'm fitting, although I would assume that all available ones would march to the same beat. Mine was from Heritage if my memory serves me correct, or possibly C&C
Another thought though, spoke to a friend over the weekend about this whole "front or back outlets" issue, and he's running as I've done/described above, he's got discs up front, his braking is spot on, and has been for a number of years!
I'm going to bleed the system through tonight, adjust up the shoes/handbrake (as this is the first spin of my new straight axles too!) and give them a whirl. Wish me luck!
Cheers
Will
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Re: Dual Circuit Master Cylinder Plumbing
by MrPotatoHead » Wed May 09, 2012 6:41 am
OK, tried to bleed the system last night and problems!
Rears bled first (remember these are on the rear outlets of the MC) and all went OK, then tried the front. After a pressure pump (three pumps, hold and release nipple) the pedal dropped, as you would expect, then hit a hard stop half way down. Got under the bus and pulling the pedal down showed that the plunger was going half way into the cylinder then felt like it was hitting something solid thus preventing it from moving further. Wasn't expecting that!
Rear nipple then released and it bled fluid thu OK, but when tightened the pedal/MC stops half way down/in again. Took MC off and plunger pushes in OK.
Note. This locking is not pressure of fluid, it is definitely knocking on something solid in the MC.
Is the MC duff or is this to do with the whole "front or rear outlet" question that started this post. Does the front cylinder (front brakes as I've plumbed them) need to be bled first?
Thanks
Will
Rears bled first (remember these are on the rear outlets of the MC) and all went OK, then tried the front. After a pressure pump (three pumps, hold and release nipple) the pedal dropped, as you would expect, then hit a hard stop half way down. Got under the bus and pulling the pedal down showed that the plunger was going half way into the cylinder then felt like it was hitting something solid thus preventing it from moving further. Wasn't expecting that!
Rear nipple then released and it bled fluid thu OK, but when tightened the pedal/MC stops half way down/in again. Took MC off and plunger pushes in OK.
Note. This locking is not pressure of fluid, it is definitely knocking on something solid in the MC.
Is the MC duff or is this to do with the whole "front or rear outlet" question that started this post. Does the front cylinder (front brakes as I've plumbed them) need to be bled first?
Thanks
Will
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Re: Dual Circuit Master Cylinder Plumbing
by Samba63 » Wed May 09, 2012 11:40 am
And on this site the rears are at the end nearest the plunger saying the rears operate first: http://www.vw-resource.com/master_cylin ... l#circuitsSamba63 wrote:Hi Will.
The principle of dual circuit master cylinder operation....
From this link: http://www.autozone.com/autozone/repair ... 52802677d7
Dual circuit master cylinders employ two pistons, located one behind the other, in the same cylinder. The primary piston is actuated directly by mechanical linkage from the brake pedal through the power booster. The secondary piston is actuated by fluid trapped between the two pistons. If a leak develops in front of the secondary piston, it moves forward until it bottoms against the front of the master cylinder, and the fluid trapped between the pistons will operate the rear brakes. If the rear brakes develop a leak, the primary piston will move forward until direct contact with the secondary piston takes place, and it will force the secondary piston to actuate the front brakes. In either case, the brake pedal moves farther when the brakes are applied, and less braking power is available.
When you read it like that it makes quite a lot of sense (to me included)..
Trev
Normally the rear brakes come on first (the piston inside the master cylinder closest to the pedal) and when the rears come on the continuing pressure from your foot pushes the rear cylinder a little further and applies fluid pressure to move the front piston down. If the leak is in the rear, the rear piston moves forward until a "nose" on it contacts the front piston and applies the front brakes. If the leak is in the front, the rear piston keeps moving down until the front piston bottoms out and the rear half then gets pressure from your foot.
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Re: Dual Circuit Master Cylinder Plumbing
by stu(pid) » Wed May 09, 2012 1:47 pm
Have you checked the action of the peddle without the master cylinder in place?MrPotatoHead wrote:Rears bled first (remember these are on the rear outlets of the MC) and all went OK, then tried the front. After a pressure pump (three pumps, hold and release nipple) the pedal dropped, as you would expect, then hit a hard stop half way down. Got under the bus and pulling the pedal down showed that the plunger was going half way into the cylinder then felt like it was hitting something solid thus preventing it from moving further. Wasn't expecting that!
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Re: Dual Circuit Master Cylinder Plumbing
by MrPotatoHead » Wed May 09, 2012 5:34 pm
Yep. It was absolutely fine. In fact the rears bled a treat with full movement of the pedal. It was when the nipples were nipped up, sealing the rear circuit, that the solid resistance occurred.
It's a mystery!
It's a mystery!
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Re: Dual Circuit Master Cylinder Plumbing
by Samba63 » Wed May 09, 2012 9:27 pm
Have you made sure that the pushrod is adjusted correctly?
It might be that with insufficient play in the pushrod that the pistons in the master cylinder aren't returning to their 'at rest' position.
It might be that with insufficient play in the pushrod that the pistons in the master cylinder aren't returning to their 'at rest' position.
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Re: Dual Circuit Master Cylinder Plumbing
by MrPotatoHead » Thu May 10, 2012 6:58 am
Good call. Recollection is that it's pretty snug. 1mm play needed? I've had the m/c off to take a look at it but it will be going back in tonight for another whirl before I give up and get a replacement!
While I'm at it I'm going to see if I have enough play in the hard lines to swap them over front to back.
Cheers
Will
While I'm at it I'm going to see if I have enough play in the hard lines to swap them over front to back.
Cheers
Will
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