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!:dontknow:

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...:redface:

:cheers:
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]

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]

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.

[batchman]

In my experience the MC shows failure by slowly dropping the pedal with steady pressure. I've changed an MC trying to cure soft pedal syndrome but no luck. Only fix for me was flushing fluid with the right bleed order RR, LR, LF, RF. Rock Auto has rebuilt MCs pretty reasonable.

Loosening up wheel bearings (constant battle for me) cause pad knockback which also gives soft (actually more like long) pedal. Steel lines help some, the rubber lines are almost certainly degrading by now.

For street/autocross driving I use Ford heavy duty fluid, it's got the best wet boiling point and it's cheap. Once it's been in the car a couple months it's wet. Track driving is a different story.

Good luck,
- Jeff