p24-1953 Posted January 11, 2009 Report Posted January 11, 2009 i am having break problems. i have a good firm pedal when you first hit the brakes but if you leave you foot on the pedel it will slowly drop. no air in the lines. (just bleed them) not visible leaks, so im thinking a seal in the master cylinder is leaking? this sound right? if have replaced all the cylinders and hoses already.... so where should i get a new one? Should i get a whole one , or should i rebuild mine? how hard is it to rebuild one,? how hard are they to remove? Quote
kevinanderson Posted January 11, 2009 Report Posted January 11, 2009 Mine does the same thing. And I had the MC brassed sleeved. Quote
Norm's Coupe Posted January 11, 2009 Report Posted January 11, 2009 If that is happening, you either need to have the MC rebuilt or replace it. Kanter has new ones and I believe you can still buy them from NAPA. Quote
oldmopar Posted January 11, 2009 Report Posted January 11, 2009 The master cylinder is not hard to remove but schedule a full day if you have never removed one. Once you have it off the car and apart look inside at the bore if its pitted try to clean it up with a brake hone once it is clean you can get a rebuild kit for less the $20.00 a new mc is about $200. if the pitting is bad then resleeve or replace. If you have not done your brakes in a while you also should check the wheel cylinders and hoses Most venders have the parts as well as napa or rock auto below is a link to rock auto which should show approximate cost of the parts http://www.rockauto.com/catalog/raframecatalog.php Quote
busycoupe Posted January 11, 2009 Report Posted January 11, 2009 If you are thinking of replacing the mc for about $180, then perhaps it is a good time to consider upgrading to a dual mc. They do cost more($250) but are much safer. This link was posted on the forum a couple of weeks ago. I have not used their product, but it looks interesting. Years ago I had a brake hose let go on a '66 Plymouth Valiant with a single pot mc. ... Not a fun experience! I did get home OK, but I was young, stupid, and lucky! http://ecihotrodbrakes.com/chrysler_master_assemblies.html Quote
RobertKB Posted January 11, 2009 Report Posted January 11, 2009 Some have used these folks for a reline.From the links on the P15-D24.com page http://www.whitepost.com/brake.html I used White Post for sleeving my master cylinder for my '38 Chrysler. Price at that time included return shipping. Was very quick service and excellent result. I would recommend them. Quote
p24-1953 Posted January 11, 2009 Author Report Posted January 11, 2009 the repair manuel says you dont have to remove it form the car to rebuild it. is this right? it just started doing this so thats why im thinking the seals have failed, and its not a pitting issue. Is this a good thought? Quote
RobertKB Posted January 11, 2009 Report Posted January 11, 2009 It will be much easier to work on it off the car unless you have a hoist. Probably a good idea to lightly hone it even if it looks good. Reassembly much easier if off the car. No dirt around also if your car is anything like mine underneath. Remember dirt is enemy #1 of anything to do with brakes. Quote
Norm's Coupe Posted January 11, 2009 Report Posted January 11, 2009 the repair manuel says you dont have to remove it form the car to rebuild it. is this right? it just started doing this so thats why im thinking the seals have failed, and its not a pitting issue. Is this a good thought? You could do what I did to rebuild mine. I could not get mine off the car to rebuild it while laying on my back under the car. Couldn't get a pipe on the wrench long enough to get the bolts out of the bracket. So........I got in the car along with the rebuild kit and drove it about 2 miles to the shop. Gave them the rebuild kit and said, "you rebuild it". Two days later and another $85 and the job was done, including readjusting and bleeding the brakes. That was in 1995 and it's still working now. Quote
Young Ed Posted January 11, 2009 Report Posted January 11, 2009 Norm a stuck in place master cylinder might drop your resale value a little bit. You better keep this stuff to yourself Quote
Norm's Coupe Posted January 12, 2009 Report Posted January 12, 2009 Norm a stuck in place master cylinder might drop your resale value a little bit. You better keep this stuff to yourself It's not stuck anymore. They put it up on the rack and used a 4 foot pipe to get it off when they rebuilt it. Quote
Joe Flanagan Posted January 12, 2009 Report Posted January 12, 2009 I just rebuilt mine. The bore was too badly pitted to hone, so I sent the MC to Apple Hydraulics in New York. They're less expensive than Whitepost. Don't have the contact info at the moment but I'll find it if you're interested. Here's how it turned out: I would suggest taking it off the car to work on it. I think it would be a nightmare to try it otherwise. I bought a rebuild kit from Roberts. They're easy to do. Just soak the inside of the cylinder and the parts with brake fluid because everything goes together easier that way. Also, the piston will only go in one way. That will be obvious when you look at it. You have to install the collar first, where the pushrod enters the cylinder. Then all the parts load in from the rear end of the cylinder. Here's an exploded photograph of the internal parts: Quote
Norm's Coupe Posted January 12, 2009 Report Posted January 12, 2009 what causes the piting? Rust. Quote
RobertKB Posted January 12, 2009 Report Posted January 12, 2009 Norm's answer is a bit too succinct. Rust is the final cause of the pitting but it is caused by water absorbed by the brake fluid. Some members have switched to DOT 5 as it does not absorb water like DOT 3. However, this includes basically rebuilding your entire system including master cylinder, wheel cylinders, hoses, and steel lines although some just flush the lines well. The two types of brake fluid are not compatible. My three flatties are kept in a heated garage and this really helps avoid water absorption. Get something cold and when it warms up eventually it causes condensation which is absorbed by the brake fluid. Overtime comes rust and the pitting. Quote
Joe Flanagan Posted January 12, 2009 Report Posted January 12, 2009 So if I used DOT3 to lubricate the parts of my MC when I rebuilt it, does that mean I am now committed to DOT3? How incompatible are the two? There is no fluid in the system right now. Everything is rebuilt. I only used the DOT3 to dampen the MC parts when I put them together. Quote
oldmopar Posted January 12, 2009 Report Posted January 12, 2009 So if I used DOT3 to lubricate the parts of my MC when I rebuilt it, does that mean I am now committed to DOT3? How incompatible are the two? There is no fluid in the system right now. Everything is rebuilt. I only used the DOT3 to dampen the MC parts when I put them together. I do not think that would be enough to cause a problem but you could flush the system with break clean or I think alcohol to be safe. I used dot 5 silicone in about a 1/2 dozen vehicles no complaints except the price about $30 a quart at napa. You can also use the newer dot 4 which is compatiable with dot 3 and to make thinks more confusing there is a dot 5.1 that is not compatiable with the scilcone but may be compatiable with the dot 3 or 4 or at least a replacement 3 or 4 Quote
RobertKB Posted January 12, 2009 Report Posted January 12, 2009 So if I used DOT3 to lubricate the parts of my MC when I rebuilt it, does that mean I am now committed to DOT3? How incompatible are the two? There is no fluid in the system right now. Everything is rebuilt. I only used the DOT3 to dampen the MC parts when I put them together. I would recommend disassembly and cleaning and then reassembly soaking everything in DOT 5 as you put it together. Quote
p24-1953 Posted January 12, 2009 Author Report Posted January 12, 2009 how can you tell if its pitted to bad? Quote
Niel Hoback Posted January 12, 2009 Report Posted January 12, 2009 I would think that if you have to hone it more than a few thousandths to get past the pits, thats too much. It would make the bore too big for the cups to seal tight enough. Even a light honing removes some metal, so be careful with your speed and keep it well lubed with brake fluid. Stop often to see if the pits are going away. You can get an idea how much you are removing by watching how much metal is in the fluid. Quote
Don Coatney Posted January 12, 2009 Report Posted January 12, 2009 how can you tell if its pitted to bad? Any visible pitting makes it too bad. Any pitting you can catch a fingernail on makes it too bad. Needs to be pristine. I will not attempt to define pristine but that is what it needs to be. Quote
p24-1953 Posted January 27, 2009 Author Report Posted January 27, 2009 update.... you can rebuild a master cylinder while it still on the car with out any problem. it took about 2 hrs to disassemble/ rebuild and bleed the system. no major pitting, but the cup was torn, so i guess that was the problem. Quote
RobertKB Posted January 27, 2009 Report Posted January 27, 2009 Congratulations. Sounds like an easy fix. I assume you did not hone it then but as Don C. said earlier the bore needs to be pristine. Quote
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