QuestionDick, I've never really worked on cars before. I have a 1951 plymouth 4 door. The brake pedal started having little resistance and now goes all thewayto floor I think I found the master cylinder under the car below the drivers seat. #1 Is that it? #2 What do you think is wrong? #3 Can I fix it myself? Do you know of anyone in Raleigh N.C. I can take it to? Help.
THanks Mike
AnswerThere are quite a few possible reasons for the pedal going all the way to the floor. The master cylinder is located where you spotted it, but it is by no means the only possible explanation for your problem.
To diagnose your problem and get it fixed right the first time requires a multi-step process:
Step one: Check the fluid level in the master cylinder. There will be a little "door" in the floor over the fill cap - get a can of DOT 3 fluid from your local auto parts place and fill up the reservoir. You'll need a large wrench to get the top of the master cylinder off. These are various sizes, so you'll need to take a look at it and perhaps measure across the flats to see what size wrench you need. On the other hand, if you have a medium sized "Channellock" wrench, you may be able to get it with this. It will probably be on there pretty tight, assuming it hasn't been serviced in a while.
If the fluid level is within 1/2 inch of the top of the master cylinder reservoir, then your problem is almost certainly the master cylinder itself. You cannot fix this yourself unless you have some experience with honing cylinders, and the special tools required. Most auto parts places will send your master cylinder away for rebuilding for you - I think that is the safest bet. If you want to try it yourself, get a rebuilding kit and a brake cylinder hone and give it a go, but if there is signifigant pitting in the bore of the master cylinder, you are beating on a dead horse, you need to send it away for professional rebuilding.
Step 2: Once you get it full or nearly so with brake fluid, put the cap back on and start pumping the brake pedal rapidly, all the way from the top to the floor board. You may have to do this 387 times, but keep it up until your leg gets tired, then do it some more! If you are lucky the pedal will come back to life and you'll have brakes again, at least for a little while.
Step 3: Now, press down hard on the pedal for a few minutes - if it sinks toward the floor while you are pressing on it, you know you have some leakage somewhere. Inspect the inside of each tire for fluid running down, and also inspect the garage floor under the car to see if you can spot the leak. If you can, that is the first thing to fix. If the pedal doesn't sink toward the floor, that means your problem is a little less severe, but I am sure it will recur.
I think you need to take the car to a pro and have the brake system thoroughly inspected, you may have a seeping wheel cylinder, one or more bad wheel cylinders, a pinhole leak in one of the steel brake lines, or a failing master cylinder. I cannot guess at the probabilities here, you need to check them all, and make no assumptions until you have all the data. Remember when you are working with brake fluid that it is alcohol based, and will ruin any painted surface of plastic it comes in contact with.
You are about as far from me as possible (I'm near San Diego!), so I cannot advise you on a good local mechanic. However, these brakes are very conventional, anyone who has been in the brake repair business for 20 years or more is going to know exactly what to do to fix your car.
Good luck. You have one of the worlds most trouble free cars - just get these bugs worked out of it and you can drive it for years without worry.
Dick
