TC brake question

[AlexM]

My 1946 MG TC has a brake problem that is somewhat enigmatic to me, considering my past experience (limited). Initially, when I depressed the brake pedal I got no brake action. There are no visible hydraulic leaks. So, I opened the master cylinder reservoir, and it is full. I then closed it. After that the brakes worked. Is the master cylinder intermittent? Is that something that can occur? I've never encountered that before. == Alex in Maine, TC 1321 --- This email has been checked for viruses by AVG. https://www.avg.com

[Norman Verona]

Alex, Clean the master cylinder cap. There is a vent hole in the cap which if blocked can cause a vacuum in the M/Cylinder

 

[b][u]Norman Verona aka "Email Norman"[/u][/b]

11 Cherry close, Royston, S71 4LZ

Mob: 0741 9905 741

Web: www.frenchblat.com

 

[b]From:[/b] mg-tabc@yahoogroups.com mg-tabc@yahoogroups.com> [b]On Behalf Of [/b]AlexM alexmm@roadrunner.com [mg-tabc] [b]Sent:[/b] 28 August 2019 23:57 [b]To:[/b] MG-TABC List mg-tabc@yahoogroups.com> [b]Subject:[/b] [mg-tabc] TC brake question

 

 

 My 1946 MG TC has a brake problem that is somewhat enigmatic to me, considering my past experience (limited). Initially, when I depressed the brake pedal I got no brake action. There are no visible hydraulic leaks. So, I opened the master cylinder reservoir, and it is full. I then closed it. After that the brakes worked. Is the master cylinder intermittent? Is that something that can occur? I've never encountered that before. == Alex in Maine, TC 1321 --- This email has been checked for viruses by AVG. https://www.avg.com

[Eric Worpe]

Hi Alex, It's tempting to suggest that the air bleed hole in the lid is blocked and that this somehow effects the seal between the cup washer in front of the piston and the bore of the master cylinder. I admit I've not been able to reason why a build up or absence of pressure in the reservoir should have such an effect, but removing the lid would allow normalization of the pressure, which seems to return the braking function. Another possibility comes from the use of a non-Lockheed rubber sealing cup washer. I've found that some replacement rubber seals have a quite thick edge to the cup, unlike the original Lockheed seals which are feather edged and are flexible enough to maintain contact with the bore. A further issue could be the absence of the special dished washer that resides in the cup and whose splayed out fingers help press the side of the cup washer against the bore. The combination of a non-Lockheed cup seal and absence of the dished washer have resulted in an inability of the cup washer to seal against the bore and consequently present as a brake failure. The pedal can be pushed to the floor, but is unable to pressurize the hydraulic system as fluid simply flows past the cup seal. When your brakes fail, does the brake pedal go to the floor? Regards, Eric. ________________________________________ From: AlexM alexmm@roadrunner.com My 1946 MG TC has a brake problem that is somewhat enigmatic to me, considering my past experience (limited). Initially, when I depressed the brake pedal I got no brake action. There are no visible hydraulic leaks. So, I opened the master cylinder reservoir, and it is full. I then closed it. After that the brakes worked. Is the master cylinder intermittent? Is that something that can occur? I've never encountered that before.

[Duncan]

Might also need bleeding.  Bubbles can tend to get caught in the front rubber lines.  A vacuum bleeder is handy.

On Wednesday, August 28, 2019, 04:24:30 PM PDT, norman verona norman@frenchblat.com [mg-tabc] mg-tabc-noreply@yahoogroups.com> wrote:

  Alex, Clean the master cylinder cap. There is a vent hole in the cap which if blocked can cause a vacuum in the M/Cylinder

 

[b][u]Norman Verona aka "Email Norman"[/u][/b]

11 Cherry close, Royston, S71 4LZ

Mob: 0741 9905 741

Web: www.frenchblat.com

 

[b]From:[/b] mg-tabc@yahoogroups.com mg-tabc@yahoogroups.com> [b]On Behalf Of [/b]AlexM alexmm@roadrunner.com [mg-tabc] [b]Sent:[/b] 28 August 2019 23:57 [b]To:[/b] MG-TABC List mg-tabc@yahoogroups.com> [b]Subject:[/b] [mg-tabc] TC brake question

 

 

 My 1946 MG TC has a brake problem that is somewhat enigmatic to me, considering my past experience (limited). Initially, when I depressed the brake pedal I got no brake action. There are no visible hydraulic leaks. So, I opened the master cylinder reservoir, and it is full. I then closed it. After that the brakes worked. Is the master cylinder intermittent? Is that something that can occur? I've never encountered that before. == Alex in Maine, TC 1321 --- This email has been checked for viruses by AVG. https://www.avg.com

[Steve S]

More than once I've seen this happen on a TC that has sat for a while. One of the cylinders ends up with air in it and the pedal goes to the floor on the first press, then slowly builds as you panic and hit it a couple more times. Try bleeding the brakes to see if one cylinder expels a bunch of air. It's also possible to suck in air if you have a sticky wheel cylinder, or if the shoe return springs are missing or weak. - Steve Simmons, TC8975 On 8/28/2019 3:56 PM, AlexM alexmm@roadrunner.com [mg-tabc] wrote:

My 1946 MG TC has a brake problem that is somewhat enigmatic to me, considering my past experience (limited). Initially, when I depressed the brake pedal I got no brake action. There are no visible hydraulic leaks. So, I opened the master cylinder reservoir, and it is full. I then closed it. After that the brakes worked. Is the master cylinder intermittent? Is that something that can occur? I've never encountered that before. == Alex in Maine, TC 1321 --- This email has been checked for viruses by AVG. https://www.avg.com

[Alex]

Thank you for taking the time to respond, Eric. In answer to your question, when the brakes failed the pedal did not go to the floor. It just felt like there was no "back pressure" on it. Now that I've opened the reservoir lid and closed it the brakes are working again. == Alex

On 8/28/2019 7:54 PM, Eric Worpe E.Worpe@surrey.ac.uk [mg-tabc] wrote: > Hi Alex, > It's tempting to suggest that the air bleed hole in the lid is blocked > and that this somehow effects the seal between the cup washer in > front of the piston and the bore of the master cylinder. > I admit I've not been able to reason why a build up or absence of > pressure in the reservoir should have such an effect, but removing > the lid would allow normalization of the pressure, which seems to > return the braking function. > Another possibility comes from the use of a non-Lockheed rubber > sealing cup washer. I've found that some replacement rubber seals > have a quite thick edge to the cup, unlike the original Lockheed seals > which are feather edged and are flexible enough to maintain contact > with the bore. > A further issue could be the absence of the special dished washer > that resides in the cup and whose splayed out fingers help press > the side of the cup washer against the bore. > The combination of a non-Lockheed cup seal and absence of the > dished washer have resulted in an inability of the cup washer to seal > against the bore and consequently present as a brake failure. The pedal > can be pushed to the floor, but is unable to pressurize the hydraulic > system as fluid simply flows past the cup seal. > When your brakes fail, does the brake pedal go to the floor? > Regards, > Eric. > ________________________________________ > From: AlexM alexmm@roadrunner.com > > My 1946 MG TC has a brake problem that is somewhat enigmatic to me, > considering my past experience (limited). > > Initially, when I depressed the brake pedal I got no brake action. > > There are no visible hydraulic leaks. > > So, I opened the master cylinder reservoir, and it is full. I then > closed it. After that the brakes worked. > > Is the master cylinder intermittent? Is that something that can occur? > I've never encountered that before. > > --- This email has been checked for viruses by AVG. https://www.avg.com

[Alex]

Steve, I will pull the drums and inspect the cylinders and retunr springs. Many thanks for your reply. == Alex, TC1321 On 8/28/2019 10:33 PM, Steve S mail@mgnuts.com [mg-tabc] wrote:

More than once I've seen this happen on a TC that has sat for a while. One of the cylinders ends up with air in it and the pedal goes to the floor on the first press, then slowly builds as you panic and hit it a couple more times. Try bleeding the brakes to see if one cylinder expels a bunch of air. It's also possible to suck in air if you have a sticky wheel cylinder, or if the shoe return springs are missing or weak. - Steve Simmons, TC8975 On 8/28/2019 3:56 PM, AlexM alexmm@roadrunner.com [mg-tabc] wrote: My 1946 MG TC has a brake problem that is somewhat enigmatic to me, considering my past experience (limited). Initially, when I depressed the brake pedal I got no brake action. There are no visible hydraulic leaks. So, I opened the master cylinder reservoir, and it is full. I then closed it. After that the brakes worked. Is the master cylinder intermittent? Is that something that can occur? I've never encountered that before. == Alex in Maine, TC 1321 --- This email has been checked for viruses by AVG. https://www.avg.com

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