Hey,

I own a 74 Valiant Duster; it is the Mexican version of the US Dart Sport. My blue baby is not in very good shape and needs immediate attention. I have been driving it often for the last couple of months and the brakes kept losing grip.

I took it to the shop and they said it was the diaphragm of the power brakes booster, they replaced it and the brakes worked fine for a day. The next day the brake pedal plunged all the way down. I checked the break fluid and the secondary reservoir (the small one) was empty. I filled it up and checked the brakes, they worked fine all day… but then the next morning it was the same.

I called the shop and told me that they only fixed the booster and that everything else was fine… the weird thing is that there is no visible leak on any tire, there are no spills… where is the fluid going? Also the brake light that is just beside the idiot light in the instruments cluster never goes off; could it mean that something is wrong with the combination valve or any of its components like the pressure differential switch?

Just so you are aware, I am not a mechanic and have no technical training at all, I just love my Duster and its slant.

I have not taken it to back to the shop yet, and when I take a ride (checking the fluid first and making sure it is full) sometimes one of the tires (I believe the rear left) locks, specially on low speed breaking.

As an extra comment, when my booster was fixed, the engine just don't feels right, it keeps hesitating specially when cold, I suppose it affected the engine’s vacuum. What can I do to fix it?

Any advises?

Cheers,


Ed.

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My other car is... another DUSTER!!! .·.

If the rear left is locking thats likely the one leaking - just because you don't see it doesn't mean its not leaking, you'd likely have to take the wheel and drum off all together. The smaller reservoir is for the rear brakes, so that goes with your situation.

The engine hesitating may be a vacuum leak - maybe the hose isn't on right or the booster itself is leaking?

One thing to remember about the booster - if it fails, your brakes will not fail, it will just take more foot force to get the same braking power. Loosing brake power all together and pedal plunging to floor is not a booster problem, but a line, master cylinder, caliper, or wheel cylinder problem.

i had a similar situation on my front brakes...the pedal went to the floor and the large pot in the MC was bone dry. i also could not see leak but the passenger side drum was locking constantly...
as it turned out a number of things happened: for one, the rubber line ruptured causing part of the leak. the wheel cylinder was also faulty and i believe is where most of the leak was from...don't really know. all i know is after several hours of working on it, the brakes work better than ever!
good luck!

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My Dart
GO VOLS!
It's not rocket science, we're just splitting atoms.

Yup, check the wheel that's locking up; chances are you'll find your leak. Also, a master cylinder can leak out the back. With manual brakes the fluid will dribble down the firewall and peel the paint and foul the carpet or floormat on the inside. In the case of power brakes it could be contained inside the booster and give you no visible evidence of a leak.

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David Kight
'62 Valiant Signet, White
'98 Dodge Dakota
'06 Jeep Liberty

Growing older is unavoidable but growing up is strictly optional.

Thank you guys... found the leak in the locking wheel...

I'll keep you posted.

Ed

_________________
My other car is... another DUSTER!!! .·.

while you're at it you would be wise to replace or rebuild the opposite side wheel cylinder too. Many times when you fix one side the increased line pressure will blow out the other side soon after.

_________________
David Kight
'62 Valiant Signet, White
'98 Dodge Dakota
'06 Jeep Liberty

Growing older is unavoidable but growing up is strictly optional.

Thank you David, very good advise... will do it.

Ed

_________________
My other car is... another DUSTER!!! .·.