Jump to content

Recommended Posts

Hopefully this is an easy fix.... Recently my 53 pontiac has started seeing some actual road miles since a 6 year frame off oil leak repair started and is now finished.. all systems work,... clutch, brakes, electrical.... My issue is this.. on short trips, no hard braking all is fine... On a longer trip, say 20 miles, in local traffic, when I get home the brake lights are still on. So what I do is unhook battery.... next day, cold system, hook up battery, lights go out and function properly.. l'm thinking brakes need bled again..?..  Brake system is 100% new. Brake switch is a pressure switch, not mechanical. Think I have a bubble inline somewhere... What do you think.....  Driving truck gives me too much time to overthink problems some times.!!  Thanks, John 

Link to post
Share on other sites

Be carefull that.  a vent hole in the master cylinder is not clogged or partly. There is vent between the reservoir and piston.It aids in letting fluid pressure off quickly when the pedal is released .

Worse case often seen is in stop and go traffic the brakes slowly build up pressure till the brakes drag or locked up and the car won't budge.

 If you wait the pressure drops eventually and you go.

Forcing to drive car with the brakes dragging will heat up the wheel cylinders and render the wheel cylinders useless as the seal cups over heat and get ruined..They blow out and leak..no brakes.

  • Like 4
  • Thanks 1
Link to post
Share on other sites

This is not a bubble or a bleeding problem. It is one of the 3 things already mentioned in this thread. Either the port in the master cylinder is blocked, the pushrod is too long, or the switch is defective.

 

By the way, I don't trust these switches any farther than I can throw them. On the day I went to pick up my 36, the brake light switch shorted to ground, and probably would have caught the wiring on fire if I had not been really quick about disconnecting the battery. If there is any question at all about the condition of the switch, replace it.

 

 

Edited by Bloo (see edit history)
  • Like 3
  • Thanks 1
Link to post
Share on other sites

Had the same issue on my 52. Brake lights were on, pedal got hard and all four wheels got hot. Short trip, no problem, longer trip exactly that happened. 

Changed the master cylinder, got a new one from CPR. Problem solved, peace of mind. 

  • Like 1
  • Thanks 1
Link to post
Share on other sites

Some brake pedals have a seal or pad around the shaft of the pedal, where it passes through the floor. It can stop the pedal from returning all the way up to the resting position. There for keeping pressure on the rod going into the master cylinder. The return spring on the pedal might not be strong enough to smash this seal on the firewall side, or you could be missing the return spring. All answers above are correct.

  • Like 1
Link to post
Share on other sites

Thanks Xander... still looking... no floor panels in the car so that rules that out..... brakes were adjusted to just eliminate any drag.... car stops straight and smooth, forward and reverse..... no pulling right or left... I have about 4 inches of travel on pedal to a solid stop.... how far should the pedal move until brake lights activate ?.... 

Link to post
Share on other sites

Pedal travel can be used with a different type of brake light switch. You are working with a pressure switch. If working properly, lights will come on with very little travel. To give a distance of travel, involves a lot of things like ratio of pedal and pivot point. Much easier to have a beer and skip the math.

  • Haha 1
Link to post
Share on other sites

Frame mounted... original... waiting for helper..(wife) will try pushrod adjustment... have beer and patience, so far... side note here.. took about 90 minutes for lights to go back out after a 10 mile short trip, light braking on rural roads.

Link to post
Share on other sites

If you can have the pressure switch pointing downhill. That way no air bubbles can get trapped in the switch. If it took 90 minutes for the lights to go out. That is a clear indication that you are not drinking a premium micro brew.🤔😆

  • Haha 1
Link to post
Share on other sites

Ha... PA's finest here... Yingyang.!!.. well, rod adjustment didn't  work but I  did find adjustment nut was loose. Had high hopes for a while... Too nice to work on it today. Road trip !! Tomorrow rain so it's going to have to wait.....

20210327_122026.jpg

  • Like 1
Link to post
Share on other sites

Had similar issue with my '37 Roadmaster, but brake pedal also worked toward no travel and very hard. 

Turned out that who ever previously assembled master cylinder got the slotted cupped washer on the wrong side of the ball at the master cylinder end of the rod,

causing the internal piston not to entirely clear the internal "bleed hole".

Problem solved !

Link to post
Share on other sites

Thumbs up for that Yungling stuff!   I grew up just outside of Pottsville so it was the home brew and served in every bar.  When I was just a young lad my dad would buy 3qts for $1.  This has absolutely nothing to do with a brake issue other than a slight diversion in activities.

  • Haha 2
Link to post
Share on other sites

To get back on topic, here is the brake switch fitment data from my Standard / Blue Streak catalog.  Your switch covers a lot of applications.  

 

EED398E1-CF4F-4FB2-8D1E-2F8D67929FA0.jpeg

Link to post
Share on other sites

The reason checking the pedal pushrod was recommended (I suspect, as I'm not the one who said it), is that too much length would not allow the brake pressure to release. I concur that it is a good thing to check.

 

Inside a master cylinder at the bottom of the reservoir are two tiny holes. The cup MUST go back far enough that the tiniest hole is uncovered, or pressure will remain in the brake system. If the adjustment is right on the edge, it can change with heat and expansion. You can see this cup clearing the hole with a bright light and some magnification if the cylinder is near empty on some cars. Probably not this car due to the tiny filler port and the fact that the master cylinder is mounted down low. You would just have to make any or all brake pedal and pushrod adjustments according to the shop manual, and then trust it is OK.

 

Regarding the pressure switches, you will find they do not trip as easily as mechanical switches, so the brake lights do not come on as early as you might expect. Some of the newer production switches have a different suffix on the number. It is because they trip on less pressure than the old ones. This is desirable.

 

.

Edited by Bloo (see edit history)
  • Like 1
Link to post
Share on other sites

Per your 100% rebuilt brake system,

What brake fluid did you use?

DOT-3 ?

DOT-4 ? Less hygroscopic, so less likely to precipitate condensation than DOT-3

DOT-5 Pure Synthetic?

 

While I'm not peersonally aware, I've read that some older brakelight switches have been reported to fail with induction of DOT-5. The synthetic fluid may, or may not have been the actual cause when using an old NOS/NORS switch - but could be the case if an existing switch, previously exposed to DOT-3 is now subjected to DOT-5.

Link to post
Share on other sites
  • 3 weeks later...

Update to all.... sorry for the delayed response.... changed switch.... seems to have fixed problem... just in time... Carlisle next week !!!!

Also, thanks to all who took the time to think it out with me ..... sometimes I still overthink the obvious.....  John

  • Like 1
  • Thanks 1
Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...