Master cylinder

Mach1 Ian · Nov 15, 2006

A question from the UK
I have a 70 auto Mach1 which has just had a front disc conversion kit with power booster fitted, the kit is a SSBC and i have changed the brake pedal to suit the kit and the problem is that the fluid in front bowl on the m/c is forced into the rear bowl and then out of the rear seal up to the power booster, SSBC exchanged the faulty m/c through Mustangs Unlimited where i got the kit from and the replacement m/c is doing exactly same as the first one.
I have been in touch with SSBC who have said they have never had this problem before, i have sent the pictures of the installation as they asked and i am now waiting for their reply.Could the problem be any other than the seals failing in both m/c's?

Thanks for any help
Ian

ford65stang · Nov 15, 2006

jcode68 · Nov 16, 2006

Mach1 Ian said:
... the problem is that the fluid in front bowl on the m/c is forced into the rear bowl and then out of the rear seal up to the power booster...

Never heard about this type of problem. Can you post a diagram or pics of how you have this plumbed? Are you getting pressure to the calipers? Were you able to bench bleed the MC before putting it in the car?

Mach1 Ian · Nov 16, 2006

jcode68 said:
Never heard about this type of problem. Can you post a diagram or pics of how you have this plumbed? Are you getting pressure to the calipers? Were you able to bench bleed the MC before putting it in the car?

The mechanic who fitted the the kit followed the instructions to the letter and i have also checked the instalation as well, i will try and post pictures of the plumbing, yes i am getting pressure the calipers and the MC was bench bled before fitting. The brakes seem to work OK when the fluid is topped up but after a couple of miles the pedal seems to get harder to press and the brakes aren't as efficient as they were.
http://i17.photobucket.com/albums/b99/baldrickmk2/Mastercylinder006.jpg
http://i17.photobucket.com/albums/b99/baldrickmk2/Mastercylinder005.jpg
http://i17.photobucket.com/albums/b99/baldrickmk2/Mastercylinder004.jpg
http://i17.photobucket.com/albums/b99/baldrickmk2/Mastercylinder003.jpg
http://i17.photobucket.com/albums/b99/baldrickmk2/Mastercylinder002.jpg
http://i17.photobucket.com/albums/b99/baldrickmk2/Mastercylinder001.jpg
http://i17.photobucket.com/albums/b99/baldrickmk2/Iansmach13.jpg
i hope you can get an idea of the plumbing from the pictures, not the easiest place to get the camera.

Thanks
Ian

jcode68 · Nov 16, 2006

Well, it looks like it is plumbed properly based on the way I recently plumbed mine (front disc swap/rear drum). Wehn you say it comes out of the seal at the booster, do you mean the seal on MC cover or are you talking about leaking into (internally) the booster? It's not possible to have the front resevior fluid pumped into the rear by way of any plumbing, they are completely seperate. The only thought that comes to mind is you are supposed to have residual pressure valve plumbed inline for the rear brakes (I think). On the 68 Stangs, this is plumbed from the factory in the connections made on the rear end, where it splits off to each wheel cylinder. Did you replace hoses and tubing for the rear brakes? I assume this did not happen prior to the SSBC upgrade?

Edbert · Nov 16, 2006

I'm confused here, the two bowls are not connected to one another, that is why they are preferable in the first place. If fluid is leaking out of the bowl it has to be one of only a few things...

The lid is not on tight.

A fitting is cross-threaded or loose.

The piston or it's seals (inside) is faulty.

Loss of fluid should be fairly easy to locate, I mean if it is leaving the bowl it has to go "somewhere". Trace the lines to each caliper or slave cylinder, they could be the culprit themselves, or at any point in the line too. If I understand correctly you are getting fluid INSIDE the booster, that can only mean the piston is the likely source of the leak.

Mach1 Ian · Nov 16, 2006

Edbert said:
I'm confused here, the two bowls are not connected to one another, that is why they are preferable in the first place. If fluid is leaking out of the bowl it has to be one of only a few things...

The lid is not on tight.

A fitting is cross-threaded or loose.

The piston or it's seals (inside) is faulty.

Loss of fluid should be fairly easy to locate, I mean if it is leaving the bowl it has to go "somewhere". Trace the lines to each caliper or slave cylinder, they could be the culprit themselves, or at any point in the line too. If I understand correctly you are getting fluid INSIDE the booster, that can only mean the piston is the likely source of the leak.

Thanks for your help,the seals on the piston failing is the conclusion we came to as well but SSBC said they hadn't experienced this problem before.
The lid is on tight and there isn't any leaks on any other part of the brake system and the fluid leaks from the rear seal on the piston an no where else at all and in answer to the question in the previous post by jcode68 there were no problems at all until the conversion kit was fitted.
I have just got a e-mail from Mustangs Unlited stating the SSBC are shipping me another MC, this will be the third, so i hope third time lucky.
I will keep you informed about the MC saga.

Thanks for all your help
Ian

Mach1 Ian · Nov 16, 2006

Edbert said:
I'm confused here, the two bowls are not connected to one another, that is why they are preferable in the first place. If fluid is leaking out of the bowl it has to be one of only a few things...

The lid is not on tight.

A fitting is cross-threaded or loose.

The piston or it's seals (inside) is faulty.

Loss of fluid should be fairly easy to locate, I mean if it is leaving the bowl it has to go "somewhere". Trace the lines to each caliper or slave cylinder, they could be the culprit themselves, or at any point in the line too. If I understand correctly you are getting fluid INSIDE the booster, that can only mean the piston is the likely source of the leak.

Thanks for your help,the seals on the piston failing is the conclusion we came to as well but SSBC said they hadn't experienced this problem before.
The lid is on tight and there isn't any leaks on any other part of the brake system and the fluid leaks from the rear seal on the piston up to the booster and no where else at all and in answer to the question in the previous post by jcode68 there were no problems at all until the conversion kit was fitted.
I have just got a e-mail from Mustangs Unlimited stating the SSBC are shipping me another MC, this will be the third, so i hope third time lucky.
I will keep you informed about the MC saga.

Thanks for all your help
Ian

jcode68 · Nov 16, 2006

Ian,
Putting the pieces together, it sounds to me like the pushrod between the booster and MC is not adjusted properly. Based on the symptoms, I would say it is too long, which causes the pressure to build higher in the system since it doesn't allow the MC piston to completely disengage. This would also explain why the pedal becomes very firm. It is highly unlikely to have back to back MC's fail in the exact same manner. Check the pushrod.

Mach1 Ian · Nov 16, 2006

jcode68 said:
Ian,
Putting the pieces together, it sounds to me like the pushrod between the booster and MC is not adjusted properly. Based on the symptoms, I would say it is too long, which causes the pressure to build higher in the system since it doesn't allow the MC piston to completely disengage. This would also explain why the pedal becomes very firm. It is highly unlikely to have back to back MC's fail in the exact same manner. Check the pushrod.

Thanks, i will get the mechanic to check that before no.3 is installed
Thanks again,
Ian

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