This has me stumped. Problem: low to no brake pedal. I installed a new CPP dual master cylinder with booster in my 1957 Chevy truck. It is all drums. It has all new lines and brakes. CPP said it did not need any additional valves. It did not come with master cylinder bleeder kit, so I installed it as is and bled the brake lines at least 10 times at each wheel (starting at the outermost wheel cylinder). I bled the lines at the master cylinder multiple times, Now when I bleed any line there does not appear to be any air in the lines, I have used the pumping the brake method and a brake bleeder tool. Everything at the lines seems fine when I bleed them, but I still get no pedal. At this point any thoughts regarding what to do next would really be appreciated. Thanks, don
Here are some possibilities to check : - Maybe it needs check valve(s). - Maybe you have one of those rare systems that doesn't want to bleed for some reason. - Maybe the master cylinder push rod has no freeplay with the pedal released. - Maybe the the master cylinder bore is too small. - Maybe your pedal linkage is incorrect. - Maybe the cylinder piston is sticking instead of fully returning when the pedal is released. Good luck
Just went through something similar. Had to stop and take the time to adjust each wheel. Amazing what a little bit out of adjustment can do to make the pedal feel funny.
Bench bleed it first as was stated above. You can get an inexpensive brake bleeding kit from your local auto parts vendor for about $10.
Try all the stuff "cuttaway" said but it could be a bad master cylinder, I had one years ago and it would bleed from one side to the other if y memory seerves me right, I am sure some one will correct me if I am wrong, booster takes away peddle also , good luck
As other have said are your brakes adjusted correct. If you have new shoes,may want to camfer ends of shoes. depth 1/8 back 1/2" Another way when you think your adjuctment is right,pull drum and measure 9-3 oclock.Should be 1/8" less then drum.If you push them out to 1/8 less then drum. Most likly they will hit on top, camfer to fit.
The master itself needs to be bled by itself kit or not They call that bench bleeding, do it at the bench or on the car. If you do it on the car be careful not to get too aggressive with the pedal.
yup i say shoe ajustment and e brake ajustment if your getting fluid out the bleeders than it should work. you pump the pedal and have some one try to spin a wheel
Also check the rod adjustment that goes into the booster itself. You will have to remove the master from the booster. You will see a hex head on the end and it is threaded. When you seat the master cylinder down onto the booster before you bolt it down solid, you want that rod/hex head end to just touch the "push rod" that goes into the master cyl and it should have a little pressure on it. I've been doing booster/master cylinder conversions for a long time and you would be surprised how far off they are from the factory!
check the pushrod length on the pedal. the ratio may be wrong. i had a simular problem and found the rod out of adjustment.
I'm not too hip on squashing the brake hoses to see if they hold pressure but all of the other advise/answers/ questions is what I would say or ask myself. It is a drum/Drum brake master cylinder? there should be a spring loaded check valve behind both of the tubing seats in the cylinder. If the parts puller pulled the wrong cylinder that could be an issue. On an Ot rig a while back I had a bad flare on a tube that wouldn't seal and drove me crazy for a week or more. You could get good pedal and drive it a ways and then the pedal would get mushy again. tighten the adjusters up until the drum locks and you can't turn the wheel and then back each one off 11 clicks. You have to feel drag on the shoes when you rotate the tire or the brakes won't work right. Make sure that you have at 1/2 to 3/4 of an inch of free travel at the pedal before the pushrod starts moving the piston in the master cylinder.
Clamping off brake hoses is the best way to destroy them if nothing else. Take the thing off,bench bleed it and go from there.
Clamping off brake hoses.... you are not a brake spe******t, hate to be the one to break the news to you. Bob
Pinching brake hoses closed is so common that special brake hose clamps and pliers can be bought. Although I think it's a bad idea, pro mechanics get away with doing it all the time. With a little finesse and technique it's normally possible to get by without bench bleeding a master cylinder and save some time as well. But, if things don't go well you may end up wasting more time than it wo09uld have taken to bench bleed in the beginning. If the cylinder is already moving fluid bench bleeding provided no benefit and proper bleeding will get all the air out of the master cylinder.
It is possible to get a bad master once in a while, which is why when I do one I use some newer application I can get at a parts store - it just saves time if I need to replace it. How are the lines run, is there any metering or proportioning valve? Sometimes it can be a pain in the *** to bleed through those. A pressure bleed usually beats that problem.
Did you do the test to see if there is a vacuum leak at the booster? I had a similar problem and found a vacuum leak due to a missing gasket where the booster and master cylinder bolt together. It took me a while to find it as I also thought it was a bleeding problem.
Let me jump on the "adjust your brakes pile". 4 wheel drum brakes give you 4 wheels that need adjusting instead of the 2 rear wheels that most of you grew up with. You can get away with some rear wheel play with disc brakes but with 4 wheel drums... a little play here, a little play there and pretty soon you have no pedal or a low pedal.
Just recently I got to the point of bleeding my brakes and had the same issue but immediately remembered I hadn't bench bled the new master after the fab up of the mount. No problem, you don't have to take it off. Just remove the lines, hold fingers over the ports and gently depress the pedal. Your finger tips are the check valves here so don't let air back in when you release the pedal. 3-4 easy pumps and you will notice no more air. Put the lines back on and proceed to bleed each wheel.
Wow! Thanks for a the replies, I now have some additional things I will try. FYI: <cite></cite>I called CPP and they will send me the master cylinder bleed kit I didn't get when I ordered it. I can also return the master cylinder, it is under warranty. Their tech support was very pleasant, no problem if i need to send it back. Thanks for the replies, appreciate your ideas. I know it is hard to diagnose problems without actually seeing them. But sometimes just getting a new perspective helps. I now see I have a few more things to check before giving up on the master cylinder. Thanks, don
After you bench bleed the master cylinder and install it then go through every wheel and adjust the shoes. It sounds like the shoes on one or two wheels are out of adjustment. You won't have any pedal if they are even a 1/4 out. That is way too much fluid to move given the size of your master cylinder.
If you are that particular, why would you be using old crusty brake cylinders? As an expert wouldn't you at least inspect them? A brake system is one place that the WHOLE system needs to be brought back to factory specs if one item is replaced. And if the customer won't go along with it, send them away. Once you touch the system you are liable for it because you were the expert, no matter what the customer did or didn't want done. I've been in court as an expert witness and have seen first hand how those situations can go.
Same **** happened to me on my CPP brake kit for my 55 Chevy truck. My problem turned out to be *******d rear calipers (4-wheel disks). Rebuilt the rear calipers, and bingo bongo, firm pedal and happy dance. Not sure why that solved the problem, but it did. So, how are your wheel cylinders?
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