chrisviktorjakematt

the brake pedal on my 78 sa has gotten very soft in the last week or so and when i press it all the way to the floor the brake light comes on. I have checked the master cylinder and found that the fluid in the front of the reservoir was very low. I filled it back up and checked for obvious signs of leaks but found none. I also took it to a local shop to have it looked at and after a quick inspection up on a lift they said everything looked ok and maybe i needed a new master cylinder.
This does not sound right to me. The fluid has to be going somewhere and it is not leaking from the master cylinder that I can see. Any suggestions would be welcomed
thanks
chris

MelWff

You should have the front calipers checked for air by bleeding them. At the same time the wheels in the front should be removed and the calipers be carefully examined for signs of leakage and the rubber hoses attached to them. Some lowering of fluid is normal as pads wear but very low sounds like a leak.

mikem350

The light is sensing a pressure loss. Low fluid in front section means a leak! Check carefully all the lines, distribution block coming from the MC and of course each caliper!!

Follow the lines all the way, and if the MC ran out of fluid you just may need to bleed the front calipers.

dochorsepower

Also the old front hoses may be "balloning" and reducing pressure. Check condition of front rubber hoses.

chrisviktorjakematt

thanks i will take the front wheels off this weekend and check myself the condition of the calipers and hoses. Hopefully something quick and easy. I am in the middle of reupholstering the seats and would like to finish that before getting too deep in brake work.

chrisviktorjakematt

So i bled the front brake lines yesterday. I did not see any evidence of leaking brake fluid on the calipers or associated areas. However when Loosened the bleed valve on the passenger side no fluid came out at all. I noticed that the caliper was closed down on the rotor and not released. I could spin the rotor by hand but could feel resistance. When my son pumped the brake pedal it finally got fluid to flow out of it. do i need to rebuild the caliper or just replace it or what

Cavu2u

I had the same problem this weekend.
Had a spongy Brake pedal action that was 1st noticed a week ago. Sunday, as I came to a stop, I noticed a red light flicker on the dash somewhere, but it went out before I could ID it. I then remembered the soft Brake Pedal, believed the light was the BRAKE light, and I was right.
Removed the Master Cylinder Cover and found the rear compartment's fluid level down to the bottom.
Looked under each rear tire; nothing obviously wet. Removed the right rear tire/wheel, and the tell-tale radial fluid stain was present on the inside sidewall. I believed it was from Brake Fluid because it foamed well when rinsed off. Carefully looked at the caliper: it was dry, as were both pads. But, the rotor side of the Brake Shield had evidence of being wet. ???
Haven't removed/inspected the driver's rear tire/wheel yet.

Steve

thegazman

When the brake light comes on from the distribution/proportioning valve your brakes need more than bleeding. You have a problem that needs to be addressed (probably a leak somewhere). Finish your upholstery, but don't drive your car until you have corrected the brake problem is my recommendation.

chrisviktorjakematt

the hoses look good but the front right caliper is closed down on the rotor. i can still turn the rotor but the caliper does not release. I guess i need to replace that caliper then do front pads up front?

chrisviktorjakematt

I have looked at the front brake lines from the mc to the calipers and have not found any obvious signs of leaks. it was hard to say by the calipers since i have a leak at the trans cooling lines that is throwing some gunk around down there but the lines and fittings and proportiong valve all look clean and dry. It must be leaking somewhere? may be the caliper that is locked up has a leak and when i replace it the problem will be solved?

Cavu2u

I had a very hard time figuring out where my brake leak was. The only way I found it, was to shine a light (brighter than just a flashlight) onto the INSIDE SIDEWALL of each tire.
Or, remove each wheel/tire and inspect for fluid. If you find some: GREAT! You have the tire removed to better clean up the mess, and access to fix the leak. If you don't find some: GREAT! You have no leak to repair AND a chance to inspect things there! Win-Win, right?

Steve

centralcalvette

1) The light is on because you have lost fluid on one side of the switch. Some older cars it is front to rear, some it is diagonal.

2) All C3 calipers are suspect, the o ring design wasn't the best. One caliper probably failed. Check carefully. Check your calipers, lines, and hoses. Your safety comes first.

3) It can be a bad master cylinder. If you have power brakes, remove the master cylinder from the booster and look for fluid. If you find a fluid leak you should replace the master cylinder AND the booster. Boosters don't like brake fluid. If the booster has failed, it will suck fluid OUT of the master cylinder. Replacing both prevents this from being a cat and mouse game.

4) If you have manual brakes, look under the dash where the pushrod goes into the master cylinder, if it's wet or dripping you need a master cylinder.

chrisviktorjakematt

ok seats are done so tomorrow I will dive into the brake repair. I plan to replace the front right caliper that appears to be sticking closed and then I guess new pads on both front rotors? For a car that gets less than 1k driving a year i guess that orielly basic organic pads will be ok? any thoughts. If this does not fix the problem of leaking fluid I will do as suggested and remove the master cylinder from the power booster to see if it is leaking there. I suppose this will be obvious when I have it apart? Do I have to bench bleed the master cylinder after this? thanks for any and all suggestions