How do I isolate the leak?

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firefighter1

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Hey guys

Today while driving around town I had a major problem with the brakes. All of a sudden the pedal went to the floor and I had almost no stopping power. I currently have a 1971 dart with power front discs and rear drums. When I got home I looked at the brake fluid level and it was a little low but not too severe. I looked at all the lines and I didn't see any leaks or indications of a recent leak. How can I isolate the leak and or find the problem? Thanks.
 
With out seeing your car and the info you gave it sounds like you have a bad master cylinder. Mark
 
hade the same problem with an F body
it was the master,it leaks an all brake fluid
was going into the brake booster and engine
was sucking it by the vaccum line

easy test is to unbolt the master from the brake booster
and you will see if it leaks or no
 
Okay. Ill check the master cylinder. If it is leaking into the booster, do I have to replace it also?
 
Hmmm conflicting advice. To replace, or not to replace the booster....that is the question? I ordered a new master cylinder after reaffirming that there are no leaks. I hope that I don't need the booster now because I'm trying to get this little problem fixed ASAP so that I can drive the car to a show 300 miles away. Can someone please tell me why I would need to replace the booster if it is just the master cylinder that is bad? Thanks.
 
I'm "guessing" Purple Haze meant replace the MC.

I had the MC go bad on mine and I just replaced the MC. If the diaphragm is still good in the booster I can't understand changing it.

You will want to bench bleed the master before you put it on and then do the brake bleeding as usual.
 
I was talking to a buddy and he said that I could bleed the master cylinder after bolting it up to the booster but before I hook it up to the brake lines. What are the advantages and disadvantages of bleeding before and after installing? I know that I have to bleed the mc before the lines. Then I'll bleed the passenger rear line, the drivers rear, the passenger front, and then the drivers front. Hmmm am I missing anything else?

On a side note... I don't think I'm going to replace the booster since the whole brake system was replaced less than a year ago.
 
Master cylinder,.. u bench bleed it because u can do it quickly, by yourself, to get the air outta the m/c. .. and it reduces the chance of spraying brake fluid on the paint..
 
Gotcha. Is the brake fluid corrosive for paint? I'll definitely bleed the mc before I install then. Thanks for the good tips!

Ever used the one person brake pump mechanism kit where you pull the brake fluid into a reservoir by manually pumping it at the bleeder valves? If so how effective is it? Or should I just do what I already know which is old school pumping on the brake pedal with a friend opening and closing the valve?
 
Brake fluid makes excellent paint remover..!!

the vacuum pump is ace,, I use it all the time,, but you gotta remember to remove each bleeder and put grease on the threads to prevent air being sucked in past the threads..

and the old way works fine too...

to check for air after,.. with m/c cap on,, have friend pump 2 or 3 times and hold down,,, remove the cap,, have pedal released as you watch fluid levels,... any "geyser" is air,, front or back,, with the exception that,- if the rear brakes are outta adjustment,, the return springs can cause a small fluid return from the rears..
 
The one person bleeder kit is pretty expensive on Summitt website. Any cheaper places around to buy those kits?
 
firefighter1 said:
The one person bleeder kit is pretty expensive on Summitt website. Any cheaper places around to buy those kits?
Click to expand...

You can get a Mighty Vac here: [ame="http://www.amazon.com/Mityvac-MV8000-Automotive-Test-Bleeding/dp/B00265M9SS/ref=sr_1_1?ie=UTF8&qid=1344351795&sr=8-1&keywords=mighty+vac"]Amazon.com: Mityvac MV8000 Automotive Test and Bleeding Kit: Automotive[/ame]


After you bench bleed the MC, you can install it and gravity bleed the system, paying close attention to the fluid level in the MC. You will still have to go through the process of final bleeding though.
 
Sweet thanks for the link. I'll definitely buy that kit. Summitt wanted like $100+ for the same thing.
 
Badsport said:
I'm "guessing" Purple Haze meant replace the MC.

I had the MC go bad on mine and I just replaced the MC. If the diaphragm is still good in the booster I can't understand changing it.

You will want to bench bleed the master before you put it on and then do the brake bleeding as usual.
Click to expand...


That's a big 10-4.
 
Oh okay few. Makes me feel better about not replacing the booster. Ha.

I saw above that inertia said to grease the bleeder threads... How do I do this without making a huge mess?
 
"to check for air after,.. with m/c cap on,, have friend pump 2 or 3 times and hold down,,, remove the cap,, have pedal released as you watch fluid levels,... any "geyser" is air,, front or back,, with the exception that,- if the rear brakes are outta adjustment,, the return springs can cause a small fluid return from the rears.."

^^ Not really acurate. There will always be some fluid returned back to the MC reservoir when the pedal is released. If released too quickly it will jump up in the reservoir. Some fluid is also pushed back every time the brake springs return the wheel cylinders to their rested position regardless of adjustment. That's normal.
 
The bleeders on each wheel. Just unscrew them and put some grease on them and put them back in. You will get some fluid drip, I don't think it can be helped. Just have a rag handy. If you wanted to do it quicker pick up 4 new ones and have them ready, unscrew one and put the new one right in.

Sweet thanks for the link. I'll definitely buy that kit. Summitt wanted like $100+ for the same thing.
Click to expand...

I just bought one a month ago at a yard sale complete for 5 bucks. Along with a bunch of other tools.
 
Well I went down to the local auto store and bought a vacuum kit for $30 bucks new, I thought it was a fair price, especially since it was retail. I have the new ms now, but i forgot to buy some grease... Oops! I'll go back and get the job done today. Let you guys know how many thing I screw up in the process. Haha. But really I'll let you guys know what happens. Thanks for all the tips and info guys!!!
 
I took the old MC off the car and I am waiting for the paint on the new MC to dry. Is there any way that I can tell if the old MC is defective or bad by looking at it? Also while I have the MC off, can I inspect the booster for anything wrong if so what should I look for? Thanks.
 
The master cylinder get two types of leaks.Internal and external.If wxternal you will fluid where the piston is(the center of the master cylinder in the back).If there is no fluid showing you had a internal leak.Clean up the booster,bleed the master and put it on.bleed the system and your done.Should have a hard pedal when the car is not running. Mark
 
firefighter1 said:
I took the old MC off the car and I am waiting for the paint on the new MC to dry. Is there any way that I can tell if the old MC is defective or bad by looking at it? Also while I have the MC off, can I inspect the booster for anything wrong if so what should I look for? Thanks.
Click to expand...


I would look inside the booster, there should have been a foam filter between the MC and the booster, at least on mine there was, and it had disintegrated and fallen inside the booster. I had to vacuum it out as best I could and I just bought a piece of foam and made a new filter to put there. It helps keep dirt out of the booster and back of the MC.

Be careful poking around inside the booster if you do this as there is a rubber diaphragm in there, you don't want to poke it.

I would also check the check valve in the top, about ten o'clock position, it has a line that runs down to the intake for vacuum and make sure it's working just for peace of mind. It should allow air to go one way but not the other.
 
Lonewolf3165 said:
"to check for air after,.. with m/c cap on,, have friend pump 2 or 3 times and hold down,,, remove the cap,, have pedal released as you watch fluid levels,... any "geyser" is air,, front or back,, with the exception that,- if the rear brakes are outta adjustment,, the return springs can cause a small fluid return from the rears.."

^^ Not really acurate. There will always be some fluid returned back to the MC reservoir when the pedal is released. If released too quickly it will jump up in the reservoir. Some fluid is also pushed back every time the brake springs return the wheel cylinders to their rested position regardless of adjustment. That's normal.
Click to expand...

That's why I made reference to "geyser"..
 
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