Brakes...broke

joshpowell16

Registered User
1 last issue to address on my SC. 1990 SC AUTO.
ABS does NOT work. I have a brake fluid leak I traced to the proportioning valve. It looks to have a sensor the plugs into the rear of it. The fluid is Comming through the sensor. To my knowledge the sensor works. I have no lights on until it leaks enough fluid, then the light comes on. I had brakes at UTI....but not familiar with the sensors themselves.

Could a typical oring be broken....or the sensor need to be replaced?

Could that be the reason there is no ABS.?
 
That "sensor" is the ARC switch - under heavy breaking, it sets the shocks to "FIRM".

It can be replaced with the original or with the Lincoln/Mercury stop light switch (down side is, if you connect it electrically, you'll pop to FIRM on almost any braking. Up side is, it's a LOT cheaper.)

No, that has nothing to do with ABS.

Except that when it leaks, you lose enough brake fluid.

Do you have brakes at all? I.E., do the rear brakes do anything? Or do you have almost no brakes (save the 'Hit something cheap!' variety?)

If you have brakes, the ABS is working, since the ABS is also responsible for all the power boost AND the rear brakes on the Gen1 cars with the Teves Mk II Integral ABS (recognizably by the large trapezoidal reservoir).

If you DO have brakes, why do you think you don't have ABS? (That's a curiosity question, not meant to sound argumentative!)

RwP
 
That is a pressure switch used by the suspension control system to determine when hard braking is occurring so that the shocks can be switched to hard.

After a while, brake fluid will pass past the body of the switch internally, the only fix being a new switch.

You can get a new switch from the auto parts store. Standard Motor Products #PSS18. www.rockauto.com currently has a wholesaler clearance on these with a price under $40. Normally they are just under $80.

If the ABS light is on, you can pull the codes and find out why you don't have ABS. That switch has no relation to the loss of ABS.
 
I feel dumb

The other day we got a lil snow n when I hit the brakes the tires lock n I never heard nor felt pulsating in the pedal. Even on dry ground I can slam on the brakes n lock up the front tires. Still no pulsating or sign of ABS.

The car brakes smoothly except under hard pedal. I know its got air in the system....but I nvr thought it to be enough to affect anything. Since it leaks I have no doubt it got air in the lines.

Well the previouse owner had put new struts all the way around....sadly he used cheap. All the electronics for the struts are gone. N the struts are basic Monroe. I would like to reinstall the proper struts. So ill need to replace the switch. But I could do it cheap for now and get the right switch when I put in the right struts.

I think I answered my own question. Its got air in the lines. I guess it helps to just spell out the problem to see the answer. Ill look into a new switch.
 
You're aware that if you're slow enough, ABS won't kick on, right? And if all FOUR tires slide, it STILL won't kick on ...

RwP
 
yes

But I assumed 40mph was fast enough. Maybe the spungyness I felt under hard braking was the ABS? Cause if there was air it would be spungy all the time....

So I could have a working ABS system. But when it was ice all 4 could have slid. Which is why it didn't work then.
 
IF the ABS light is on. The ABS braking will not function. If the ABS Braking is not functioning, and the ABS light is not on, check and see if that light ever comes on. It should come on when you turn the key to start before releasing it. If it never comes on, someone may have yanked the bulb out so that you can't tell it doesn't work.

The only way air gets into the brakes when the system is closed is if you let the fluid get low due to the leak. Air won't go in through the leak as long as there is pressure in the system which is there as long as there is fluid in the reservoir.

If the brake pedal looses assist on the model year of SC you have, then you will have dramatically reduced braking capability. Without any assist, the master cylinder is designed such that nearly all the pressure you create from pressing on the pedal goes only to the front brakes. If you are driving in slippery conditions this can mean loss of directional control when the front wheels lock.

If that ever happens, consider downshifting in concert with braking so that the rear of the car does something to try to slow you down. But be very careful because if the car downshifts too soon, the rear can lock up and cause loss of control.

Thus it is best to fix your brakes.
 
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