Have a 73 L-48 with manual brakes. The car sat for 2 years and lost all braking. Replaced the master cylinder, calipers,rubber lines and bled 2 quarts of fluid through the system. The pedel is still very soft and can be put to the floor with little to no effort. The brakes will grab (softly) with a few pumps each use. Have only tested in driveway for safety reasons. There are no leaks in the system I can detect. Can anyone shed some light on where I should turn next to solve my problem?

 

Assuming you bled it correctly, you probably got a bad replacement M/C. Happens all the time. I disassemble them before I install them and check for rust from sitting on the shelf too long.

 

keep bleeding, 2 qts is nothing...these cars are a pain in the butt to bleed...i subscribe to the theory of lowering the rear end and raising the front of the car to allow the air that is trapped in the rear caliper cylinders to find a way out....just keep doing the bleeding and it will get better...i have my kids who help me do this, say "start,1/4, 1/2,/3/4,bottom" i open the bleeder at 1/4 and close it at 3/4....no mistakes that way.

 

i am going through this problem also. here is what i have learned.
1. dot 5 silicone fluid tends to "fizz up" so go easy on the pumping if you are using dot 5.
2. get a Mityvac or at least rent one from autozone. this helped me tremendously in troubleshooting my system leaks. one person tool.
3. this tool allowed me to tshoot front and back seperatly and then from the caliper by itself and add on hose and lines capping them off as you add on a new link.
4. even bleeders can go bad, i had to replace them all and i reinstalled with some teflon tape too.

i have no answers, just suggestions. good luck.

 

These cars are prone to getting an airlock in the system and sometimes may even need to be power bled and pedal bled at the same time.

Was the master cylinder bench bled?

Good Luck

Vettedesk

 

Ok...here is my take. I think everyone will agree they are a PITA to bleed. I tried the DOT 5 in a completely new system and finally gave up. As already stated, it forms tiny bubbles which counter your effort. I started over with DOT 3 and was only half successful. I followed a buddies suggestion of leaving it to gravity bleed overnight. After setting 12 hours, I went through the regular bleeding procedure and got a solid pedal in the expected time. The gremlins are in there and just need a little extra time to fall in line. Try walking away from the DOT 5 and see if you can get a pedal the next day.

 

Thanks for the replies!
The master cylinder was not bench bled and I am using DOT3. Will try to bleed a few more quarts through and see what I get. Never had a manual brake system give me this much grief. Want to have the system power bled but don't want to spend $60 to have it trailored to the shop just yet without trying things myself. Thanks again, just wanted to make sure I wasn't doing a bubba.

 

You really need to bench bleed the MC - I don't think you'll ever get all of the air out if you don't. It sounds like the problem is definetely air in the lines. You also have to go in the right order - there is some debate on this but I think it is LR, RR, RF, LF. Or RR, LR, RF, LF.

I'm sure someone can tell us which order is best. Either way, I hate doing it...

 

A few years ago.... I did a "test" for everyone here on the forum... I bled my own C3 several times (using DOT5 no less) and each time, I bled the calipers in a different, random order. Each time, I pulled and emptied all 4 calipers. There was absolutely no difference in pedal firmness with any of the bleeding orders I used, and the pedal was rock hard each time. I used gravity.... plus a hose & a coffee cup... no special tools.

But.... the "old school" says furthest to closest is "correct".

 

Bleeding volume through the M/C is not the ticket... you have to follow proper procedure.

 

I too have a 73 with manual brakes... now we know why Shelby had to add stickers to the dash of the GT350's he sold Hertz!!!

It seems you've done just about everything correctly so I would look first at the last - most obvious issue - bleeding the master cylinder.

Just have a "loved one" (keeps the cussing down!) pump the brakes and hold them while you "crack" the brake lines at the master cylinder - one at a time. (Just hold a couple of paper towels under the fitting to catch any fluid that leaks.) It shouldn't take very long and it's likely that's where your problem lies. Some of the master cylinders even have regular bleeders just above the outlets for the brake lines. If you have them, just bleed normally.

If this doesn't fixe the problem, I'd try one more normal brake bleeding and then l'd look at the master cylinder.

Just remember that even with a firm pedal (and you can get one) these manual brakes take getting used to. Even with a firm pedal you will feel like something's wrong, it's not. It just takes greater than normal pedal pressure to stop with manual disk brakes...

Good luck,

GUSTO

 

just saw this for the first time ever tonight at a local cruise in

 

MAZ73...you need to bench bleed your MC. I just installed a new master cylinder tonight and followed the instructions for bench bleeding. I can now understand how critical it is to bleed on the bench first, it would take forever trying todo it in the car. It took me at least 30 minutes on the bench before bubbles stopped coming up. I did not stop until there was not a single bubble left in the passages. There is no way this could be done in the car. You will see why when you do this....it takes a lot of fiddling, tapping on the side and different strokes to get all the air out. One done, bleeding the system was not an issue. I just used the traditional method with my son in the drivers seat. Very firm peddle first try and test drove the car tonight with some aggresive stops.

 

I most recently had this same problem with my 73' Coupe with standard disc brakes. First of all take the new master cylinder off and bench bleed it. Then you could bleed your calipers the old fashion way with a helper or Toms way of gravity bleeding. I used to do the bleeding with a helper but decided to go with a power bleeder the last time around and I will never go back. For a little more then $50 one could be purchased from Motive products on Ebay or direct from Motive. I found this tool to be one of the best tools that I have ever purchased for the money and like I have mentioned on this forum and also on the C-2 forum I don't have to beg my wife or daughter to come out to give me a hand or should I say foot and hear all the complaints about how their foot is tired or that it is to hot to be doing this. No more complaints!! With the Motive One Man Power Bleeder after setting it up, no more then 20-25 minutes later I was putting the wheels back on the car with a better pedal then I ever remember having in my 73' Coupe that I have owned for the last 23 years. I would do a search on brake problems on the forum and you can see for yourself what others think of the Motive Pressure Bleeder. You will be surprised to see how many others have gone this route. One of the most knowledgeable forum members on the C-2 forum (JohnZ) swears by it and believe me when he has something to say on the C-2 forum everyone listens. Being in the auto parts business I always heard from the repair shops that I sell to over the last 27 years that Pressure bleeding was the best and fastest way to bleed brakes. I always thought about buying one but couldn't justify the expense because they were a little expensive. Last year I was surfing around on Ebay and I put Brake Pressure Bleeder on the Ebay search line just to see what I would come up with. This is where I found out about the inexpensive Motive Pressure Bleeder and after mentioning it on the C-2 forum last year I found others who where familiar with it.

 

You will not get correct pedal without bench bleeding the master, that is a must. After that just bleed through the system and you will be on the road. Any questions on the bleeding process call: 18004420335

Thanks

Vettedesk

 

Thanks for all the great advice. Going to bench bleed the M/C this weekend and see how it goes.