Seeking some brake advice

Monte

Low Mileage
Over the summer I replaced the brake lines in my car with braided lines. This is the first time I've done something like this so it was certainly a learning experience. I was able to finish the job and the brakes were working great. It wasn't a huge improvement but they are better. Probably more from the new rotors and brake pads then lines. I put around 50 miles on the car and the brakes were working fine.

Life got in the way and I had to park the car for about 6 weeks. I finally went to drive it again yesterday and the brake pedal went to the floor. No brakes. I checked the brake fluid reservoir and it was about half full. I know I left it full when I parked it. I expected I had a leak but I could find no evidence of leaking brake fluid.

I filled up the reservoir and pumped the brakes but they never stiffened up. The pedal still just goes to the floor.

I'm thinking I may need to bleed the brakes again. I haven't had time to try that yet. Does anyone have any advice? Where did that brake fluid go?
 

EricH

Eric Hamilton
Moderator
The most likely place for the brake fluid to have gone is onto the floor of the driver's side footwell. A half-reservoir over six weeks doesn't leave a puddle, just a nasty spot on the carpet.
 

phillips82

True Classic
The most likely place for the brake fluid to have gone is onto the floor of the driver's side footwell. A half-reservoir over six weeks doesn't leave a puddle, just a nasty spot on the carpet.
Probably right. Reach up there and see if you can feel any fluid on the pedal assembly.
 

Dr.Jeff

True Classic
I hate to suggest it, but I doubt it will be just a matter of bleeding. More likely the master cylinder has gone bad. Happens easily in short time when not used regularly. It would explain the situation described by Eric (why the reservoir is half empty), as well as the pedal to the floor phenomenon (with no improvement after refilling the reservoir) that you experienced. Replacing or rebuilding the master cylinder is a bit more involved than installing SS brake hoses/rotors/pads. Might want to review the process first (I believe there is a write up on it in the Wiki?).
 

PaulD

Paul Davock
I hate to suggest it, but I doubt it will be just a matter of bleeding. More likely the master cylinder has gone bad. Happens easily in short time when not used regularly. It would explain the situation described by Eric (why the reservoir is half empty), as well as the pedal to the floor phenomenon (with no improvement after refilling the reservoir) that you experienced. Replacing or rebuilding the master cylinder is a bit more involved than installing SS brake hoses/rotors/pads. Might want to review the process first (I believe there is a write up on it in the Wiki?).
In bleeding the brakes, it is not unusual to press the brake pedal to the floor before closing the bleed nipple on the brake cylinder. With an older master cylinder this can push the seals through the unused and potentially rusty portion of the cylinder, causing premature wear or destroying them. When I did this, the brake fluid at the bleeder became dark with bits of rust and seals. I should have known better.

Paul Davock
 

Monte

Low Mileage
I checked all around the pedal box and the drivers side carpet and I'm not feeling or seeing any brake fluid. I'm hoping this is a good sign. I looked at the process for replacing the master cylinder. It sounds intimidating but I think I can handle it. Should I go straight to this step?
 

Dr.Jeff

True Classic
Should I go straight to this step?
I'd want to verify everything before replacing anything. Try to find the actual leak and inspect all components of the braking system to assess exactly what happened and what is needed. It is not a fun job to replace the master cylinder, so I'd really hate to do it and find there was some other issue causing the problem. Also, if you do end up having to replace the master cylinder, consider replacing the clutch master as well.
 

TonyK

True Classic
It's due to rust. Brake fluid is hygroscopic.
And that is why I run Silicone oil on my cars. I get about 17 years to a master cylinder before I have pedal problems. I use it in both the brake and clutch systems.

TonyK.

Grimsby Ontario Canada.
 

carl

True Classic
I would definitely try to find the leak before messing with MC replacement. I would also rebleed the system to try and get the pedal working correctly.
 

kmead

Old enough to know better
Before running around with your hair on fire, I would start with rebleeding of the brakes. It may be as simple as a bubble working it’s way back to the MC. May be.

After that I would look at the master cylinder as the culprit.

There are many how tos for doing the MC. Start with removing the driver’s seat and work from there.

Good luck and sorry for your troubles.
 

EricH

Eric Hamilton
Moderator
Should I go straight to this step?
No. You will want to eliminate all other possibilities first, partly because replacing the master cylinder is a seriously unpleasant job and partly because if unnecessary you may end up breaking something else.

Pressure bleed or reverse bleed so that you’re sure you have all the air out, fill the reservoir to the top, see if you get the pedal back. If you do, stand on the brakes HARD a few times and see if the pressure exposes a leak or the level in the reservoir goes down. Even a drop or so underneath a caliper is a problem.
Look for pinhole leaks where the hard line to the rear passes out of the passenger compartment, that’s a common spot for corrosion.
Check the metal tray underneath the master cylinder to see if it’s holding fluid.

Only if you cannot get a hard pedal and no leak anywhere else is it likely to be the master... and then I would expect to find some sign of your missing brake fluid somewhere underneath the master.
 

Dr.Jeff

True Classic
Not sure if anyone already mentioned this, but the plastic fluid reservoirs are very prone to cracking. Check to see if it may be leaking the fluid into the vent tray. Also check the supply hoses from the reservoir to the master cylinder. The original style fabric covered hoses can dry out but not be noticed due to the cover. The fabric will be soaked if the hose is seeping.
 

Monte

Low Mileage
Thanks everyone for all the great advice. I believe I found the culprit over the weekend. I moved the car around in the garage and found a small puddle under the passenger side rear brake. I tightened everything up there. (I think it was the bleeder screw that was loose) Bled all four brakes and I'm back in business! Just in time for the snow to fly here in Minnesota.
 

EricH

Eric Hamilton
Moderator
(I think it was the bleeder screw that was loose)
Yes, that would do it... very good odds that you've fixed it now.

A more remote possibility is that the o-ring around the plunger for the parking brake is leaking, in which case the rubber boot around the back of the caliper will show signs of brake fluid exposure. If you find that you're still leaking at that corner of the car and you've tightened everything up, that would be the next thing to check.
 
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