Brake system crapped out

Driving back from an upholstery shop a front brake line blew at the same time the master cylinder went Tango-Uniform. Narrowly avoided a crash. Just the rear brakes were working a little for a while before the pedal went to the metal, and the left rear cylinder was leaking as well. Glad to have AAA towing. It's been sitting at the mechanics for a week now waiting on delivery of a new master cylinder. Having them completely drain and flush the system and convert to DOT4 so we can get away from the corrosion problem from it sitting for periods of time. I've had to do the rear brake cylinders quite a few times in the past from them corroding up.

if they are unable to deliver the master cylinder let me know...I have 1 from a 1986 4wd

They just replaced the master cylinder, re-bled the brake system, and the petal still goes all most to the floor. The also adjusted up the rear brakes.

WTF???

pads recent? air still in system? flexible hoses all good (not swelling)? took em that long....bring it back.

They still have it. New front brake lines; rears look good.

They are thinking proportioning valve ...??

Quote:

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Originally Posted by ragragtimetime

pads recent? air still in system? flexible hoses all good (not swelling)? took em that long....bring it back.

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load sensing proportioning valve & spring

http://www.mightyram50.net/vbulletin...lve-amp-spring

I did not realize they were on the very early 1st gens....1983 power ram 50 4wd does not have 1.

Luv it when a garage uses your money to chase a problem.
When they tell you what's wrong with it and give you a price, always be sure to say, "and this will solve the problem, correct?"
If they don't fix it, well they will have to because they said it would. That's supposedly why they are in the business of fixing and not hoping to fix.

An Auto garage is NEVER suppose to let you drive a vehicle that is unsafe for you or anyone else on the road until it is properly repaired. If you get in an accident they can be responsible for it.

Usually pedal dropping low is a rear brake shoes issue or air in the line. Our brakes are a simple design and if the rear brake shoes are out of adjustment the pedal will drop and the E-brake can also have a long travel if it isn't self adjusting. If you hold the pedal down, does it continue to drop or is it firm. Is the fluid nice and clean now that they installed a Master Cylinder. If the shop just installed a new Master Cylinder and left the old brake fluid in, you may want to try and run over the garages owner's foot when you can.

Keep us updated!

http://www.mightyram50.net/vbulletin...5&d=1423540321

The mechanic is pretty experienced and admits this is driving him nuts. I took the factory service manual over to him yesterday and he appreciated it. Replaced the front brake line which blew out, and the other one just to be safe (I asked him to). That didn't work, so he replaced the master cylinder ...it's the original one so pretty old. That didn't solve the problem, after adjusting up the rear brakes. The petal still goes almost all the way to the floor, but will pump up some and hold. The front brakes appear to be applying a little. Had him flush out the system completely and convert to DOT4, which I have done on my other DOT3 vehicles to help with corrosion resistance. Completely bled the brake system, used about 1/2 gallon of fluid. Still the same problem. Petal goes almost to the floor on initial application. About all that's left is the proportioning valve I'd guess?? Can't believe this simple system is causing such a problem.
Any suggestions much appreciated.
I've had this shop do a lot of work for me in the past and they have always done a good job at a fair price.

Quote:

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Originally Posted by BradMph

Luv it when a garage uses your money to chase a problem.
When they tell you what's wrong with it and give you a price, always be sure to say, "and this will solve the problem, correct?"
If they don't fix it, well they will have to because they said it would. That's supposedly why they are in the business of fixing and not hoping to fix.

An Auto garage is NEVER suppose to let you drive a vehicle that is unsafe for you or anyone else on the road until it is properly repaired. If you get in an accident they can be responsible for it.

Usually pedal dropping low is a rear brake shoes issue or air in the line. Our brakes are a simple design and if the rear brake shoes are out of adjustment the pedal will drop and the E-brake can also have a long travel if it isn't self adjusting. If you hold the pedal down, does it continue to drop or is it firm. Is the fluid nice and clean now that they installed a Master Cylinder. If the shop just installed a new Master Cylinder and left the old brake fluid in, you may want to try and run over the garages owner's foot when you can.

Keep us updated!

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Can't locate a 1980 Dodge D-50 brake proportioning valve at Rock Auto or Auto Zone ... are they non-existant for the '80? Does anyone have a link to them?

Ahhhh ok, for a minute it seemed that you were getting taken for a complete brake system rebuild. Sorry!

You also have that brake booster on the firewall that is vacuum brake assist, but looks like you have it under control.
Just one of them brake Gremlins.

Part #MB277112, MB277850

1980 d-50s do not have a proportioning valve - Geronimo is an 1980 and he doesn't have one.

My 81 doesn't have a proportioning valve but it does have a pressure check valve going to the back. It's located on the left side under the box mounted on the first upright box mount. What it does is hold some pressure on the drum wheel cylinder so the springs don't pull the shoe's all the way back to the full reset.If it's faulty all the fluid will be pushed back and it will act like you just changed the shoe's and haven't pumped them up yet every time you don't use the brakes for a few minutes. Wilwood has check valves in different PSI if you can't find a replacement for the original, they also have an adjustable one.

The mystery gets worse. Went over and talked with the mechanic. He really is a nice older guy and is trying hard to figure this out without charging me an arm and a leg. The brake pedal doesn't push down hard, like it would when the vacuum booster is bad, and can pump up to about half-pedal and hold. New master cylinder. On the rack I applied the brakes while he turned the front wheels and they stopped and held, but the pedal was almost to the floor. He re-bled the system again (bleed it so many times I was able to have him convert to DOT4!) and it didn't help. Rear brakes are adjusted up properly and work. It's the pedal going almost to the floor, with minimal braking on the front, that is the mystery. On a test drive it slowed down then rear wheel locked up, so it looks like uneven braking between the rear and the front. When I left he was putting it back on the rack to trace out the brake lines to see if it really does have a proportioning or pressure check valve. Sure like to get this resolved; I need Mitzi back!
The mechanic has done hundreds of brake jobs and fixed all kinds of problems on trucks and cars and this one has him baffled ... me too!
Any other ideas what to check for the cause of the problem totally appreciated!

Mark just called and said he thinks the proportioning valve is located in a spot where the gas tank has to be dropped to get at it. Does this sound like it in the '80 D-50 Sports 2.6 liter?

I gave her a test drive and the front brakes apply now evenly with the rear. He said the repeated flushing got a lot of brown crap out the rear bleeders; wondering if the proportioning valve was hanging up and the flushing with DOT4 loosened up the crap enough to flush some and make it work again? Pedal goes down to about 1" off the floor at full stopping; right rear wheel doesn't lock up like it was doing for the past couple of weeks. With the new master cylinder is there an adjustment to make yet to get the pedal up so it doesn't go so far down before full application occurs? Driveable, but sure don't want to make too many panic stops. All together he used almost a gallon of DOT4 flushing and bleeding. I'm dreading the bill. Having the pitman arm replaced; way worn out. Poor girl wanders all over the road. Saw the proportioning valve up by the gas tank; sure looks like the original with 130,000 miles on it. Probably very tired. :-(

"Saw the proportioning valve up by the gas tank; sure looks like the original with 130,000 miles on it. Probably very tired. :-("

& is it a 4wd 3-line input load sensing proportioning valve with spring or a 2wd 2-line input check valve?

You can adjust the brake pedal stud nut from under the dash. First check to be sure it isn't already maxed out.
Attachment 13012

Okay, I'll check that out. If it's full-up is there another adjusting point without pulling the master cylinder back out?

Quote:

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Originally Posted by BradMph

You can adjust the brake pedal stud nut from under the dash. First check to be sure it isn't already maxed out.
Attachment 13012

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2-wheel type in-line by the gas tank. Tried to find a replacement using MB part number without any luck.