Author Topic: Brake fluid leaking out of top of master cylinder, 66 Newport  (Read 3633 times)

Offline Heiny57

  • Hunt and peck king
  • ********
  • Join Date: Jun 2010
  • Posts: 3827
Brake fluid leaking out of top of master cylinder, 66 Newport
« on: September 18, 2010, 08:41:25 PM »
I have been trying to improve my mushy brakes, new parts are helping, but I am leaking fluid around the cylinder cap. The normal level is 1/2 inch below top. I top it off and in 30 minutes of city stop and go it is empty.  :-\  Now with that said I noticed this thing squirts fluid up out of the reservoir if I don't have the cap on. I haven't seen that before, I think the fluid is getting up on top of the paper baffle/gasket and then coming out under cap. Is my cylinder bad causing the squirting leaks?  :D
Wake Up America

Offline Aunt Phil

  • Hero Member
  • *****
  • Join Date: Jul 2010
  • Posts: 656
  • location: Hamlin NY
Re: Brake fluid leaking out of top of master cylinder, 66 Newport
« Reply #1 on: September 18, 2010, 10:19:52 PM »
DAMN, that's a long dialback on the memory system.

Yes, they do squirt when the cap is off, and it burns like hell when it hits you in the eye.

Not sure of the transition year but the squirting was eliminated when the wrinkled balloon was added to the top of the master cyl reservoir.  They squirt too when the cap is off, and it burns just as much.

I have a feeling your fluid loss is elsewhere though.
© Aunt Phil 2010

Offline wilbilt

  • Hero Member
  • *****
  • Join Date: Jun 2010
  • Posts: 1459
  • location: Honcut, California
  • Trailer Trash
Re: Brake fluid leaking out of top of master cylinder, 66 Newport
« Reply #2 on: September 19, 2010, 01:16:37 AM »
The squirting is due to the compensating port allowing the fluid under pressure in the lines to return to the reservoir when the pedal is released. This is the small hole drilled just behind the main fluid port in the bottom of the reservoir.

When the master cylinder piston returns to the fully released position, the front edge of the rubber cup on the piston ends up just behind this port, allowing the pressurized fluid back into the reservoir. Due to the small diameter of the  port, the fluid squirts. There may also be a momentary squirt of fluid from the port when the pedal is first depressed, which is normal.

Is the MC cap rectangular and retained by a bolt? There should be a vent hole in the gasket, which may be directly over the compensating port. Try reversing the position of the gasket so the vent hole is no longer aligned with the squirting fluid.

Does it have power brakes? If so, check the vacuum line connected to the intake manifold for the presence of brake fluid. If the rear seal on the master cylinder is leaking, fluid may be getting sucked past it, into the booster and then into the intake manifold. This can empty the reservoir pretty quickly.
« Last Edit: September 19, 2010, 01:21:57 AM by wilbilt »
-- Garageless in Northern California since 1985

Offline Heiny57

  • Hunt and peck king
  • ********
  • Join Date: Jun 2010
  • Posts: 3827
Re: Brake fluid leaking out of top of master cylinder, 66 Newport
« Reply #3 on: September 19, 2010, 11:05:04 AM »
Thanks guys for input, I cut a new gasket for the cap.


 I found a vacuum leak in the small plug on the brake booster and replaced it.



 I took a wire wheel to the top edge of the cylinder to clean the rust.


I also roughed up  the glazed drums with a sanding drum, that made a great improvement.


Wake Up America

Online goodfellow

  • RestroLibrarian
  • Can use hammer
  • *****
  • Join Date: Jun 2010
  • Posts: 9632
  • location: Northern Virginia
Re: Brake fluid leaking out of top of master cylinder, 66 Newport
« Reply #4 on: September 19, 2010, 11:14:24 AM »
Just a suggestion Heiny57; looking at that booster, it might be a good idea to take it out and give it a good cleaning. Chances are that your MC has leaked into the vac diaghragm.

Offline Heiny57

  • Hunt and peck king
  • ********
  • Join Date: Jun 2010
  • Posts: 3827
Re: Brake fluid leaking out of top of master cylinder, 66 Newport
« Reply #5 on: September 19, 2010, 12:19:54 PM »
What kind of material is the diaphragm made of. Will the fluid eat it. I pulled the vacuum hose and there was no sign of fluid, I should have started it and tested the brakes, to see what kind of assist it is actually giving.  shrugx 
Wake Up America

Online goodfellow

  • RestroLibrarian
  • Can use hammer
  • *****
  • Join Date: Jun 2010
  • Posts: 9632
  • location: Northern Virginia
Re: Brake fluid leaking out of top of master cylinder, 66 Newport
« Reply #6 on: September 19, 2010, 12:34:57 PM »
It's a neoprene membrane. A leaking seal in the MC can slowly drip brake fluid into the booster and cause the membrane to fail. Pull the vac line to the booster for signs of brake fluid contamination -- a Q-tip should help. If no contamination is found, the membrane may still be toast on the bottom of the booster housing.

Offline Heiny57

  • Hunt and peck king
  • ********
  • Join Date: Jun 2010
  • Posts: 3827
Re: Brake fluid leaking out of top of master cylinder, 66 Newport
« Reply #7 on: September 19, 2010, 08:08:40 PM »
I am out of time this weekend but I will read up in the manual and maybe get time next weekend to pull them apart. What sucks is the MC is cheap compared to the booster.

But the brakes are getting better with each thing I do, I just got the front wheel cylinders to change also, Chrysler engineering makes spindle removal necessary to remove cylinder.  frustratedx 

The trouble is I am not sure how good these brakes can actually be as I remember back in the day drum brakes sucked no matter what.   :D
Wake Up America

Offline J.A.F.E.

  • Alien Wizard Of Odd
  • Global Moderator
  • Knows what a screwdriver is
  • *****
  • Join Date: Jun 2010
  • Posts: 6203
  • location: About 28000 Light Years from the Center of the Galaxy. At the moment.
Re: Brake fluid leaking out of top of master cylinder, 66 Newport
« Reply #8 on: September 19, 2010, 09:12:00 PM »
If drum brakes are in good order, the linings and friction surface of the drum are good, not glazed or grooved and the brakes adjusted properly they work well enough.

Your setup is more worrisome to me because it's single circuit I am more comfortable with dual circuit systems.
As alien as it gets.

Quote
Whatever he is it is seriously unpleasant.    No moral compass at all, no thoughts, no guilt or obligations beyond personal desires of the moment and no debts recognised if he already has the product.
                                   

Live long and 42.

Offline Heiny57

  • Hunt and peck king
  • ********
  • Join Date: Jun 2010
  • Posts: 3827
Re: Brake fluid leaking out of top of master cylinder, 66 Newport
« Reply #9 on: September 20, 2010, 06:08:15 AM »
You are right JAFE I was concerned when I bought it, one line failure and run away train.....

I am looking for a conversion to a dual.
« Last Edit: September 20, 2010, 06:55:04 AM by Heiny57 »
Wake Up America

Online goodfellow

  • RestroLibrarian
  • Can use hammer
  • *****
  • Join Date: Jun 2010
  • Posts: 9632
  • location: Northern Virginia
Re: Brake fluid leaking out of top of master cylinder, 66 Newport
« Reply #10 on: September 20, 2010, 06:23:11 AM »
......Your setup is more worrisome to me because it's single circuit I am more comfortable with dual circuit systems.

That's why I recommended a good cleaning and inspection. That booster does not instill any confidence over the "short term" -- a good dual system would go far to alleviate any potential risks. Good luck!!

Offline Heiny57

  • Hunt and peck king
  • ********
  • Join Date: Jun 2010
  • Posts: 3827
Re: Brake fluid leaking out of top of master cylinder, 66 Newport
« Reply #11 on: September 20, 2010, 06:49:46 AM »
 thumbsup2
Wake Up America

Offline Aunt Phil

  • Hero Member
  • *****
  • Join Date: Jul 2010
  • Posts: 656
  • location: Hamlin NY
Re: Brake fluid leaking out of top of master cylinder, 66 Newport
« Reply #12 on: September 20, 2010, 10:59:52 AM »
The dodge power wagon guys seem to favor Chevy pickup parts for conversion to dual MC.

Another possible is 68 Mopar MC & booster
© Aunt Phil 2010

Offline wilbilt

  • Hero Member
  • *****
  • Join Date: Jun 2010
  • Posts: 1459
  • location: Honcut, California
  • Trailer Trash
Re: Brake fluid leaking out of top of master cylinder, 66 Newport
« Reply #13 on: September 21, 2010, 05:55:58 PM »
I am out of time this weekend but I will read up in the manual and maybe get time next weekend to pull them apart. What sucks is the MC is cheap compared to the booster.

But the brakes are getting better with each thing I do, I just got the front wheel cylinders to change also, Chrysler engineering makes spindle removal necessary to remove cylinder.  frustratedx 

The trouble is I am not sure how good these brakes can actually be as I remember back in the day drum brakes sucked no matter what.   :D

I will also chime in and recommend an upgrade to a dual circuit system. 1967 was the year they became commonplace, although not mandated until 1968. Finding a suitable donor these days might be a problem, though.

If the spindles are two-piece or have bolt-on steering arms, you should be able to access the wheel cylinder bolts by simply loosening a few things instead of having to remove the spindles. It has been a long time, though.
-- Garageless in Northern California since 1985

Offline Heiny57

  • Hunt and peck king
  • ********
  • Join Date: Jun 2010
  • Posts: 3827
Re: Brake fluid leaking out of top of master cylinder, 66 Newport
« Reply #14 on: September 22, 2010, 05:25:20 PM »
Thanks for the info guys.  Will I somewhat miss described the situation, I have to take the backing plate loose from the spindle, air gun time and it is at the other garage.  frustratedx    If my booster is bad I may as well buy the newer year parts.  I will post the question over at the Mopar site.
Wake Up America

The Garage Gazette

Re: Brake fluid leaking out of top of master cylinder, 66 Newport
« Reply #14 on: September 22, 2010, 05:25:20 PM »

Tags: