Hey Ya'll It's been awhile since I've been online. I got my 72 Mav running and I promise next time to post pictures. Anyway, I've got another problem. I have drum brakes on the front. The brakes are very soft. I have to pump them to come to a stop. I initially thought it was air in the lines but it is not getting any better. If they are pumped slowly, they will build up pressure. They are not keeping pressure and I have to pump and pray everytime I have to stop. I am not used to having drum brakes in the front. Is this the master cylinder or is this the drums? Also the front chamber on the master cylinder is slowly leaking. As always, any help is greatly appreciated.
I agree with our esteemed colleague from Kentucky. Make absolutely sure you bench bleed the master cylinder before you install it.
Well, this post answers my question too. The new MC has been on the car a while but I just recently got around to bleeding the brakes and cannot seem to get the air out. I wonder now if I should buy a new master cylinder -maybe I'll try 'bench bleeding' this one first and go through the whole routine again (rr, rl, fr, fl - about 3 times). If that doesn't work, I'll get a new one I guess. Thanks guys.
If you didn't bench bleed the master first, you have a lot of air in the lines. You will need to bleed all four wheels. Yes, I agree with everyone else. You need to replace the master cylinder. Sounds like you are leaking past the seals, especially if you can see it on the firewall. Otherwise, you have an internal bypass.
Make sure you adjust the drums as well. The pads should drag on the inside of the drums. When the wheel is raised and you spin it the wheel should stop after a few turns. If they are spinning freely they are not adjusted correctly and will give you a very soft/low pedal ...
something that I do not own (yet) but will soon is a pressure bleeder ...... kinda like a pressure garden sprayer but it attaches to the m/c and forces fluid through the sytem to each wheel cylinder/caliper .... an added bonus is that it also replaces all the old fluid while removing all the air ......Robert on a side note, the purchase is needed for our 77 vette that is a ^%$*&^ to bleed the brakes ..... there is 4 pistons PER CALIPER on that car and all 4 wheels are disc ...... also 2 bleed screws per caliper on the rear ...... the best brake pedal so far has been obtained by gravity bleeding (open m/c, fill, open all bleed screws, get beer, check m/c, fill, tap calipers to dislodge air, get beer, check m/c.....ad nausem)
I agree with Jason. If your m/c is leaking, that is probably the problem. But where is it leaking to? If you don't have fluid leaking out of the master cylinder at the cylinder it could be leaking in a line or wheel cylinder. Pull your drums and look at the wheel cylinders and inside of the drum. It should be dry and not oily with brake fluid. Seth
check your wheel cyls.if there is no signs of leakage,check all your lines,from the m/c going to each wheel.if those check out,as stated above,check the adjustment on each wheel cyl.with the car up in the air,spin the wheel.you should here a slight dragging sound.if all the above check out,more than likely the piston in your m/c flew south,not letting any pressure build up. good luck and post what you found out. chuck.
Sounds like everyone has a handle on this one But one thing I want to say is make sure if you get any brake fluid on your paint MAKE SURE you clean it very quickly. brake fluid can damage paint and it doesn't take long to do so.....
Quick Funny Story...... Quote- comet dad "something that I do not own (yet) but will soon is a pressure bleeder ...... kinda like a pressure garden sprayer but it attaches to the m/c and forces fluid through the sytem to each wheel cylinder/caliper .... an added bonus is that it also replaces all the old fluid while removing all the air ......Robert" One thing you gotta be careful with those is that you don't release the hose that pushes the brake fluid into the MC. Funny Story- I was about 17 and helping my dad bleed the brakes on his Corvette- All original with 42k miles on it. We were using the pressure bleeder and we didn't think it was working, so I said what if I do this and took the hose off the top of the MC. Well, in the end there was tons of fluid all over the engine and the factory original paint, and we all know how well paint and brake fluid go together! Well, I thought I was a dead man, but he ended he was happy cause there was never so much comound, polish and wax on his car every! And it looked good! Ever since then he doesn't allow me too close to that Corvette.....And now he's jealous that my mav is faster than his vette Just a funny one I thought I would throw in there......
If you are adding fluid, there is a leak somewhere. As said, pull drums and look for fluid and check lines for leaks. Also, could be a wheel cylinder froze up. This will make the pedal go down. Backyard mechanic check is have someone step on brake as wheel(s) are jacked up. If you can spin wheel, the cylinder is froze up. If it's been froze a while, you can usually tell when you pull the drum and see the pads and drum are not as shiney as they should be. Could also pull drum half-way off and have someone step on brake to see if pads come out. Don't do this with drum off or everything could fly apart when brakes are applied.
