Model A Brake Master Cylinder Unit - Help needed

  • 61xlch
  • 61xlch's Avatar Topic Author
  • Offline
  • ACD Club Member
  • ACD Club Member
More
04 Jun 2022 18:21 #45509 by 61xlch
Who can assist with insights and recommendations regarding the brake cylinder unit?
I rebuilt it carefully and complete, but it doesnt operate as needed.
Even after numerous bleeding procedures and double checks I am not able to achieve a constant pressure at the pedal. With countless pedal moves down to the floor it builds up a pressure, but after sitting half an hour it needs to be pumped up again.
Any ideas and experiences appreciated.
Thanks
Andreas
Berlin/ Germany

Attachments:

Please Log in or Create an account to join the conversation.

More
06 Jun 2022 18:47 #45526 by hessacres
Replied by hessacres on topic Model A Brake Master Cylinder Unit - Help needed
Bleeding is a major chore. It is much easier if you use a brake bleeder that you connect to your air compressor. You can find them on Ebay for around $20. If you are loosing pressure that fast you clearly have a leak somewhere., look for fluid loss. What fluid are you using, I used DOT 4 after considerable flushing everything with denatured alcohol( until I did no see any visuable contamination). I also used hi temperature (white) lock tight on some threads to get good and tight and it seems to hold up to brake fluid, especially at the hose connections. Did you replace the hoses, mine were cracked to the point they weeped fluid when I got my car. I started the bleeding process at the master cylinder bleeder, then the right rear, then left rear, then right front then left front. Then the high one on the firewall that goes to the brake pressure gauge. If you are using a hand pump bleeder it is considerably harder to near impossible. Lastly do you have the original bleeders on the car. Someone in the past put some newer style on my car and they did not seal correctly, but when I replaced with original style they worked much better. I still have to re-bleed the system every year or two some especially the right front wheel for some reason. The car looks great, but to keep that way you do need good brakes. They may be hydraulic, but they are not ABS, and that is a heavy car.
The following user(s) said Thank You: 61xlch

Please Log in or Create an account to join the conversation.

  • 61xlch
  • 61xlch's Avatar Topic Author
  • Offline
  • ACD Club Member
  • ACD Club Member
More
06 Jun 2022 20:11 #45527 by 61xlch
Thanks George.
Regarding your hints: I used DOT5 silicone fluid, all hoses are new, no leakage outside. I am pretty sure it's bleeded 100%.
Must be a problem inside the master cylinder.

Please Log in or Create an account to join the conversation.

  • mikespeed35
  • mikespeed35's Avatar
  • Offline
  • ACD Club Life Member
  • ACD Club Life Member
More
07 Jun 2022 04:15 #45530 by mikespeed35
Replied by mikespeed35 on topic Model A Brake Master Cylinder Unit - Help needed
Did you sleeve the master cylinder?
CORDially MIke

Mike Huffman

Please Log in or Create an account to join the conversation.

  • 61xlch
  • 61xlch's Avatar Topic Author
  • Offline
  • ACD Club Member
  • ACD Club Member
More
07 Jun 2022 06:44 #45531 by 61xlch
Hello Mike,
Its been reamed and honed and fitted with a new oversize piston and new made rubbers. After achieving a considerable pressure it holds the pressure and does not fall through.

Please Log in or Create an account to join the conversation.

More
07 Jun 2022 15:17 #45532 by RandyEma
First of all I have never had any luck with silicone brake fluid . And I have been making the small booster cyl cups out of teflon which seems to hold the lip much better
The following user(s) said Thank You: 1748 S, 61xlch

Please Log in or Create an account to join the conversation.

Time to create page: 0.223 seconds
Powered by Kunena Forum