I have a set of Speed Bleeders to install on all 4 wheels but noticed something peculiar that I want to ask about before I start. I plan on installing the Speed Bleeders and bleeding the whole system shortly but want to be sure what I'm dealing with. When I get into the car, before I start the engine, the pedal is firm. When I start the engine up, the pedal gets soft and goes closer to the floor? Is this normal for a brake system that just needs to be bled or not? The car has less than 50,000 miles and was maintained well by my cousin who had owned it since 1980 ish! Thoughts and experiences are appreciated.

Take care,
OLE442

 

It is normal that the pedal moves towards the floor with the engine running (vacuum boost), but soft pedal can be many things.

1. old fluid with water contamination ( water compresses more )

2. Air in the system, due to rotor run out , leak in the system

3. Worn down brake pads with high rotor run out. More travel for the piston to move.

4. master cylinder seal allowing by pass under high pressure ( vacuum booster assist )

So before you start a bleed check the fluid condition , check for caliper leaks , rotor run out , pad condition.

Too check for caliper leaks it is best to remove each wheel and remove the brake pads and look for wetness at the caliper pistons. This finds small leaks.

To prepare for brake bleeding I found it is best to pressure bleed, so you can purchase a motive pressure bleeder , or do something similar to this.



If you have never bleed Corvette brake system , be prepared for frustration. Attention to detail is required to get this right.

As a start , if the fluid looks reasonable run a line from the bleeder back into the MC (recirculate the fluid) just to see if there is air in any line.

Once you have done each line and no air retest to see if you get a firmer brake pedal.

Touching / Bleeding Brakes on the C3 corvette is frustrating for a lot of people on the forum. Search for soft brakes. Seems like a quite common frustrating process.

 

Yes its normal and it feel slightly different than with the motor off. The vacuum will give a different feel than just pushing on it with the motor off because you are just using the hydraulics alone

 

The pedal height also drops as soon as I start the car up. It drops maybe an inch? The fluid in the MC is full and it is pretty clean looking.

 

Nur - mall.

 

yep....your fine

 

hope you have better luck with the speed bleeders than I did. couldn't get them to stop leaking. went to harbor freight and got a pneumatic brake fluid bleeder and sucked out all the old fluid and pulled in new fluid. easy to see when all the air is out of the line. just keep the master full of fluid.i recently used it to suck the oil out of the rear diff. worked good !