Brakes went to the floor driving home tonight. (Page 1/3)
RotrexFiero DEC 07, 09:34 PM
Never had a problem with my brakes, but tonight on the way home they went to the floor. Just frightening.

I was able to pump them to stop the car.

I drove to work the brakes were fine. Fiero sat for about eight hours, it was 30 degrees out.

I drove home had to pump the brakes, but by the time I hit my street they were solid.

I check the brake fluid reservoir it was fine.

Vacuum was fine.

Any ideas what to check next?

Unless I isolate the problem it's just too dangerous to drive.
Mike in Sydney DEC 08, 01:12 AM
Check to see if you have a dragging or stuck calliper. Happened to me once. Calliper piston was stuck and the resultant heat boiled the brake fluid. Hit the brakes and the pedal went to the floor. Could pump and get some pedal pressure to stop with. When the brakes cooled it was like the problem never happened.
RotrexFiero DEC 08, 08:04 AM
Thanks for you reply Mike.....I dont think it's a dragging or stuck caliper, I didnt at least feel any pull or lagging.

I ordered a new brake master cylinder.

Not taking any chances.

I'm wondering if the cold weather froze or shrunk the old seals in the old one. Is this something that happens?

I am lucky I noticed the problems as I drove, and not tried to make a hard stop and hit someone.
RWDPLZ DEC 08, 11:20 AM
Classic symptom of a burst line, usually the metal lines, not the rubber. Turn on the car and pump the pedal a dozen times. Check under the car for a puddle or drip, check all wheels to see if one is wet (burst hose).
RotrexFiero DEC 08, 02:12 PM
If the line burst I would have not brakes at all. That was not the case...I have no fluid leak.
RWDPLZ DEC 08, 02:42 PM

quote
Originally posted by RotrexFiero:

If the line burst I would have not brakes at all. That was not the case...I have no fluid leak.



No, if a line bursts you still have some brakes, just like you described. The Fiero like most modern cars has two distinct brake circuits, allowing the car to still stop if one circuit fails, just with increased pedal pressure/excessive pumping. It's a redundant safety circuit. That's been a thing since like the 70's. I had a line burst in a drive-through once, I was able to nurse the car home pumping the brakes like you described above, one of the old rusty lines finally let go at one spot. Pittsburgh is definitely in the rust belt.
RichLo1 DEC 08, 02:49 PM

quote
Originally posted by RotrexFiero:

Thanks for you reply Mike.....I dont think it's a dragging or stuck caliper, I didnt at least feel any pull or lagging.

I ordered a new brake master cylinder.

Not taking any chances.

I'm wondering if the cold weather froze or shrunk the old seals in the old one. Is this something that happens?

I am lucky I noticed the problems as I drove, and not tried to make a hard stop and hit someone.



You did the right thing by ordering a new master, and yes you are correct that is exactly what happened.

Usually a master with a worn seal 'creeps' to the floor at a stop light but the cold temps exaggerated that symptom drastically
Patrick DEC 08, 04:05 PM

quote
Originally posted by RotrexFiero:

I drove to work the brakes were fine. Fiero sat for about eight hours, it was 30 degrees out.



I'm curious. In regards to the "cold temp" theory... was your car sitting overnight (before driving to work) in a garage that was warmer inside than the temperature was outside?
theogre DEC 08, 07:42 PM
Cold temp won't cause above problem.
"Pedal to Floor," No leaks and maybe "restore" brakes by pumping either bad MC or Fluid Boiling.

Replace MC and expect 1 or 2 Quarts of New Fluid to "flush out" the system.
See my Cave, Brake Service

Before replacing MC...
Try to see all calipers bleed screws open.
If not... You likely need calipers and maybe soft hoses too.

⚠️ Warning: Often you won't feel Pad dragging. More so if on the rear axle.
You might find 1 pad is worn more then same on other side but may not be a dragging problem.

If can see the brakes thru the wheels then easy way is use IR to read rotor temp.
Drive then Quickly Read both on same axle. Should be close to same. Front vs Rear maybe way different.
See my Cave, IR thermometer

w/ this setup
Inner pad dragging is often piston problems.
Outer pad dragging is often slider problems.

Plus fluid boil often happens easier because of wet fluid. Most cars > 10 years often have wet to very wet fluid.
That's why often need 1 quart or more new DOT4 fluid...
See my Cave, Brake Fluid
Before you ask, cheap "Pen style" testers are unreliable at best. Don't buy them.

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

RotrexFiero DEC 08, 08:04 PM
My Fiero is garage kept and has low miles. Never seen snow, maybe once or twice. No rust. I replaced the brake lines with SS a while back.

No way that I boiled the brake fluid. It was 30 degrees out and I had only driven a mile.

No fluid seen around wheels or on the floor. Fluid level is normal.

I was fortunate I was not going sixty on the highway.

I worry about old parts. Maybe the weather did not cause this condition, cause if it did we'd all be in trouble. But, maybe it didn't help. I know nothing about the MC.

What is the longevity of these parts? I've never owned a car that was 35 years old. Even if its not the problem its getting swapped out!!!!