Brake advise on wife's beater car needed.

[moparguy]

I'm about to the throwing things across the shop in frustration trying to get the brakes up to stuff on the wifes beater work car. It's a 1988 Dodge Dynasty we bought new. Has 3. 0 engine with non-ABS brakes and something over 250K on it.



She complained a few days about the pedal going way to far down and having to pump the brakes to stop. Well, a quick look didn't reveal any fluid around the inside of the wheels indicating a seal problem so I diagnosed the master cylinder as being bad.



Replaced it, had a bit of trouble bleeding the air from left rear cylinder, finely test drove it in front of the shop and proclaimed it good to go. Next day she comes home said it still wasn't right.



Well I've spent the better part of this evening trying to get the air out of the left rear side of the system. Ever time we start to get a pedal, all of a sudden, it goes away and more air starts to appear. I've used a 1/2 gal. fluid trying to bleed this thing.



Can't find any leaks, and I've done this type stuff for 30 years. I just pulled what I know in my heart is a good master cylinder off to return for a different one in a act of desperation.



The thing that blows my mind is I can't find any place I'm losing fluid, and hence letting air in.



Any help is appreciated.



Ronnie

 

[jwoelfle]

I'd bet money on a bad master. I have seen them bad right out of the box... on a Pherd I used to own as a matter of fact. I just went thru that on a master on one of my motorcycles. I went thru almost 2 liters of DOT4 before I gave up and got another rebuild kit. Second time was the charm.



Good luck



Jim

 

[dpuckett]

I replaced the master cylinder on Mom's Celebrity at about 220K. Never has been right; I put 3 "new" ones in; none was different from the other. THe pedal has to go down too far in my opinion for decent braking, and it is frontend heavy. Mom thinks it's great, so I can live with it.



Moparguy-

How are you bleeding the brakes? I put a clear piece of tubing over the bleeder screw, other end in a bottle of old fluid, and pump the pedal, or have someone pump the pedal, until there is no more air. Naturally, you have to refill the master cylinder, or you will end up bench bleeding it again. Worked to get the air out. ALso, how many ports come out of the master cylinder? I have found that using the plugs in the ports is a lot better way (in my experience, anyway) to bench bleed than using the hoses looped back into the MC, esp if there are 4 lines coming out.



Daniel

 

[moparguy]

Thanks for the replys. I'm using clear plastic hose into a pint jar to bleed the air. And I do use the plugs to bench bleed the master cylinder.



The strange part is how is air getting into a sealed system when I haven't found a leak, yet.



RJR

 

[jwoelfle]

I know you know this but air can only be coming from wheel cylinder seals, caliper seals, brake hose connections, or the "new" master cylinder. Chances are that if you don't see any fluid around the wheel cylinders, hoses, or the calipers, it's gonna be an internal leak of the master cylinder. Since you've already put out the money for the new master, I'd yank it back off and take it back to the store and get another one. After installing the second new one, if it still isn't right, start looking harder at the other items.



Is the new master really new or rebuilt? Is it from a good parts supplier or someone like Autozone? If it isn't a new unit from Wagner, Raybestos, or Mopar, I'd REALLY point at a bad rebuild.



Just my opinion.



jim

 

[moparguy]

Well, Jim nailed it. The master cylinder was the weak link. I pulled it last night and this morning the wife swapped it out. Bled the air from the replacement on the work bench, installed it and a short while later all the air was out of the system and the brakes work.



I still haven't figured out how the master cyl. was letting air into the system, but it was.



The only thing is now wife says the pedal goes down further than it used to, even though the car stops fine.



It never seems to end.



Thanks for the help all.



Ronnie

 

[jwoelfle]

You pulled it last night AND YOUR WIFE REPLACED IT THIS MORNING? You mean you've got HER turning wrenches... FOR YOU??!!:--)



You ARE my hero!!



Seriously, glad it worked out for ya. As for the brake pedal going further, could just be the displacement of this master is a little different from your original. As you know, that master may fit many Mopar products and the rebuilders aren't about to specialize in the one for your car. They just take the average, if you will, in the specs of all the vehicles it will fit and build it that way.



Jim

 

[moparguy]

 

[Eric Kahn]

Air will leak in through the seal at the end where the rod goes through, also if fluid is leaking out through that seal, it will be sucked into the engine since that is the vacumm side of the diaphram