Brakes

[USAFPILOT]

My brakes seem to be slightly engaged after a while driving.


At first the pedal is spongy...then after some driving it gets real firm and works quite well...but if I put the car in neutral to coast it feels like it is slowing down on the brakes a little...and once I park it in the garage it wont roll. But it will roll again once it has cooled off.

This is not due to the e-brake not being disengaged. That is the first thing I checked.

I dont want these rotors to warp up...is this normal?

[WB9MCW]

My guess is either the brakes are semi-engaged like you suspect

or you may have wheel bearing on the way out

try the wobble the wheel test while on a stand and see if you have excess play

plus let's see what others think -- even though the wobble test is easy.

[tomtom72]

Hi, I don't know if this will help as my 90 maybe different from the later cars but in the FSM Brake section there is a diagnostic outlined in the Brake Troubleshooting chart for "dragging brakes". The answer for adjusting the Brake Pedal was the closest match to my symptoms, so I used that soloution as a starting point.

In my 90 it's so simple that I thought it was a miss-print. It said make sure the brake pedal is at the proper height by pulling up on the pedal. I did this and heard some clicks and the pedal moved! When the clicks stopped, the movement stopped. I was dumb founded, but when I tested the car the rear brake dragging was gone!

The only other answer in the chart involved the booster rod. On a 90 the rod tip has to be level with the outside face of the booster ( where the M/C bolts up ). If the push rod is too far out the booster applies enough pressure to the M/C to drag the brakes The push rod adjusts by turning it like a screw.

The only other thing I can remember is that there is an adjustment procedure for the parking brake....but I don't remember it...sorry...


Tom

[LT5-Lee]

I would suggest flushing the fluid. I had this happen one time on another car where it got so bad I had to relieve pressure just to get home. It seems a particle of trash or rust clogged the return port on the MC. I have also seen brake hoses fail and allow fluid to pass from the inner core to the outer rubber shroud and basically pinch off flow.

[USAFPILOT]

Flushing the fluid fixed it...now I am going to replace the pads and install some freshened up rotors and flush again for good measure. I also did a complete flush using DOT4. Ive always heard you can use DOT4 in a DOT3 system but not DOT3 in a DOT4.

I'll be using Hawk HPS pads and some slotted rotors from a previous vette. I wish I knew who made them but I know they are practically brand new and from Canada.

Should I use any additive on the pads before I install them? Ive seen that done before but I don't think it is necessary.

[WB9MCW]

Looks like Dot 4 is a good upgrade.

>>> http://en.wikipedia.org/wiki/DOT_4

I am about to do mine so I will do the same unless there is a reason not to.

"DOT3 has been all but replaced with the superior DOT4 as there is little cost difference between the two."

From >>> http://en.wikipedia.org/wiki/DOT_3

Dot 5.1 looks like the real winner even out performing Dot 5

See >> http://en.wikipedia.org/wiki/DOT_5.1

Wonder if there is any reason not to use 5.1 in our ZR-1's ???

[Kb7tif]

I think the fluid flush is a temp. fix and the master cylinder's rubber is breaking down and master needs to be replaced. mine did this.

[USAFPILOT]

Originally Posted by Kb7tif

I think the fluid flush is a temp. fix and the master cylinder's rubber is breaking down and master needs to be replaced. mine did this.

well that should be fun...shiza

[pantera1683]

Originally Posted by USAFPILOT

well that should be fun...shiza

It's not very hard to do.

[WB9MCW]

Where is a good place to get a rebuild kit for the MC on the ZR-1

Tom Henry Chevy? or any dealer? Are they available easy?

I think mine needs it since I too have the low pedal - spongy syndrome now.

Prob the orig Brake fluid in my system 63K miles now.