brake pedal goes to the floor

[LJRuddy]

Last week, a guy i work with bought an 89 SHO beater for fun. He had to do some basic maintaince on it and one of the jobs was to install new front pads. Apparently, he forgot to tighten the bleeder screw on the driver's front wheel and he emptied out his brake reservoir. He put new fluid in and bled all 4 wheels in this order: drivers front, passengers front, drivers rear, passengers rear. He bled each wheel until fresh fluid poured out. However, he is still getting the super soft brake pedal. It goes to the floor every time before it begins to slow down. I took a look at it today and i found no rusty lines, no leaks, and all of the bolts and pieces are where they should be. 89s dont have ABS so we can rule that out as the problem. Any other ideas?

 

[St Louis SHO]

rear hoses and a master cyl will fix it.

 

[LJRuddy]

How would rear brake hoses cause these symptoms?

And if the master cylinder was leaking through a seal, the brake pedal would still feel normal but after keeping the pedal down for a bit, fluid would leak out of the cylinder and cause the brakes to loose pressure resulting in the pedal going to the floor... Make sense?

 

[St Louis SHO]

Well, after the pedal went to the floor, it pushed the piston past a lip if the MC is OE, tearing the seal inside. They wear just like anything else.

 

[naval-avi8or]

That's also not the correct bleeding order.

 

[dcmeigs]

I'm having the same sort of problem in my 93 ATX. Pedal all of the way to the floor. Replaced master cylinder with rebuilt. OK for a day. Replaced again. OK for a couple of days. Replaced ABS unit. OK for three days. Pedal all of the way to the floor. No a drop of fluid is leaking. WTF?

Shotime1979 recommended replacing the rear hoses. Why?

What am I missing?

And naval-avi8or, what is the correct bleed order? (by the way, I owe you a few cold ones for all the correct advice you have offered over the years)

 

[1993MTXSHO]

direct from the service manuel:

l RH Rear

l LH Front

l LH Rear

l RH Front

 

[baySHO_510]

I would bleed it again. Start from the rear passenger, then rear driver, then front passenger, then front driver. When you bleed them dont "pump up" the pedal... just step on it ONCE and hold it down while someone else opens & closes the bleeder screw. It makes it easier both people yell out "up"... "down" to avoid opening the bleeder screw while the pedal is up & you let more air into the system.

Do this as many times as it takes to get all of the tiny air bubbles out of the system. It helps if you get a small clear plastic line & attach one end to the ****** of the bleeder screw & the other end emptying into a container. Not only do you not make a mess but you can see the little air bubbles coming out... this way you know for sure when no more air is coming out.

Keep us posted, I think this should take care of the problem.

 

['94SHO]

Ummm, don't forget to bleed the master cylinder after you do the brakes.
This is overlooked many times.. Also, when compressing the fronts, don't go
crazy with the clamp. (If you use one.) You can force the piston too far into the bore. My brother-in-law did this once on my crown vic interceptor, and he almost hit his corvette getting my car off the ramps. Of course, normal people
usually don't do this, but he is a Gorrilla with 20 in. arms, and breaks things by
over tightening them. So, in short, bleed the master cylinder.. should help.

 

[DeepPower]

I recently had the same problem. Went to stop, pedal went to the floor. And by that I mean that the pedal travelled further than it usually does. When that happens, it's usually either tiny fluid leak or lots of air in the brakes.

For me, it was one of the rear brake lines - I could see the rust on the line, but I couldn't see the brake fluid leaking because it was coming out of a pinhole leak. I replaced all the rear brake lines, problem fixed!

Look for rust on the rear brake lines. Scratch away at the rust with your finger, you should get to either bare metal or your finger will get wet.