Car brake question

[MHBill]

Hi All,

I have a 98 Taurus SE with disk brakes front and drum brakes rear. When turned off or driving, pedal pretty much goes to the floor. When driving it will do about the same thing. But the front brakes seem to lock up and it feels like hittin the front brake on a bike and the rear coming up.

I don't see anything obviously leaking, fluid level maybe a little low. Took the rear drums off brake cylinders are very dirty covered in "soot", but not wet looking. Couple of the seal caps are torn.

Car was not driven over the winter and I am trying to decide if it is the master cylinder or the rear brake cylinders. The way it acts I am leaning towards the latter. Trying to save money without throwing money at it.

Appreciate your thoughts and tips

Bill

 

[Bob_VT]

Re: Car brake question

Ford's have a proportional valve valve and it sounds as if your rear brakes are not working and only the front. You will probably need to bleed the brakes to get it to reset.

Check your master fluid and see if one side is low.

You might have sucked up some crud in one side.

 

[RogersJetboat454]

Re: Car brake question

Hi All,

I have a 98 Taurus SE with disk brakes front and drum brakes rear. When turned off or driving, pedal pretty much goes to the floor. When driving it will do about the same thing. But the front brakes seem to lock up and it feels like hittin the front brake on a bike and the rear coming up.

I don't see anything obviously leaking, fluid level maybe a little low. Took the rear drums off brake cylinders are very dirty covered in "soot", but not wet looking. Couple of the seal caps are torn.

Car was not driven over the winter and I am trying to decide if it is the master cylinder or the rear brake cylinders. The way it acts I am leaning towards the latter. Trying to save money without throwing money at it.

Appreciate your thoughts and tips

Bill

To confirm whether or not rear wheel cylinders are leaking, I gently pull the rubber dust shield around the cylinders pistons down with a pick, and see if any latent brake fluid comes out. On a '98 car, if the cylinders are original, there is a good chance they may be leaking.

What your describing sounds a different then bad drum brake cylinders though. As Bob said, it sounds like you are only getting one channel of your brake system working, and as you suspect the master cylinder may be an issue.

Also....
I'm not 100% on the year of you car, but I know at least on older Taurus's, Ford used a funky proportioning valve on the non-ABS cars. It was meant to sense if the car was nose diving (heavy braking) to prevent the rear wheels from locking up and spinning the car out. It is a block looking thing with brake lines going to it, and is mounted on the floor pan above the drivers side rear swing arm (one of the arms that runs from the bottom of the knuckle to the center of the chassis). It has a lever that connects from this arm to the proportioning valve, and the movement of the arm up and down regulates the pressure to the back brakes. These assembles are famous for either rotting out, or locking up tighter then a bulls &$$.

If it's shot or broken, it could certainly render the rear brakes useless.

 

[RogersJetboat454]

Re: Car brake question

Just did a little more checking...

If your car is non-ABS, I believe it has what I'm talking about. Officially it is called a brake load proportioning valve, and it looks like this;




One other thought...
I have dealt with many cars that have rotted brake lines that would hold enough brake fluid that it wouldn't dramatically pee fluid out when you stepped on the brakes, but rather the fluid would weep and ooze out, then allow air in the system. I have done front to rear brake lines on ALLOT of Taurus's from your era and older, so it wouldn't surprise me if that may be an issue, especially if you live in an area that has roads treated with salt in the winter. Might be worth putting it up on a lift, and checking all this out.

 

[mscher]

Re: Car brake question

Will the pedal pump-up and hold, after multiple pumps? If it drops, master cylinder, is where I'd look.

 

[MHBill]

Re: Car brake question

Finally found that rascally load proportioning valve. But it was getting late and didn't jack it up to get a good look. It looked kinda iffy though from below. It is a non BS.. I mean ABS car. ha

Brake lines were replaced by shop about 3 years ago. No obvious "pee" but not wet or damp anywhere that I can see without a real lift.

Pedal will not hold when all 4 on ground. Had rear tires off today and no movement in drum brakes. (pedal same felt the same way too) Maybe cause of the sensing device, when jacked up?

My first thought was master cylinder too, but why would just front brakes work and lock up? Found a test for master cylinder try that tomorrow and look at that rear valve.

More investigating tomorrow..since I have the time GRR

Thanks all.

Bill

 

[RogersJetboat454]

Re: Car brake question

My first thought was master cylinder too, but why would just front brakes work and lock up? Found a test for master cylinder try that tomorrow and look at that rear valve.

If the seals have failed in the part of the MC that handles rear brakes, it will not build the pressure to the rear. The MC is built with multiple channels so that you will still theoretically have at least some brakes to stop the car if one fails. It has been many moons since they made MC's with one channel handling all 4 brakes.

Stopping an old car with a busted and unassisted single channel MC, and drum brakes to boot must have been interesting to say the least.