C3 Spongy brake pedal.

[Frank K.]

Had front rubber hose collapse inside. Sleeved caliper removed and replaced (front) Bled bakes numerous times with clear heavy flow of fluid. Place foot on pedal still goes to floor slowly with motor operating. This all started with car pulling to right when brake was applied Whats next?

[Terry M.]

Re: C3 Spomgy brake pedal.

Had front rubber hose collapse inside. Sleeved caliper removed and replaced (front) Bled bakes numerous times with clear heavy flow of fluid. Place foot on pedal still goes to floor slowly with motor operating. This all started with car pulling to right when brake was applied Whats next?

Let me get this straight:

You replaced only both front rubber brake hoses, right?
You bled all four corners, Right?
What bleeding method did you use?
Power bleed
Gravity bleed
Two person pump and open

When you replaced the front hose(s) did the front part of the master cylinder drain all the fluid out?

[Frank K.]

Re: C3 Spomgy brake pedal.

One hose replaced ,all four corners bled, two person pump and bleed Master cylinder never drained. Did want to replace both hoses but foreign manufacture replacement was all I could find

[Stephen L.]

Re: C3 Spomgy brake pedal.

You may want to consider a total brake overhaul, including all hoses, wheel calipers and master cylinder. Do a thorough flush of the system and bleed.......

[Joe L.]

Re: C3 Spomgy brake pedal.

One hose replaced ,all four corners bled, two person pump and bleed Master cylinder never drained. Did want to replace both hoses but foreign manufacture replacement was all I could find

Frank------


I don't think you'll find anything but foreign-manufactured brake hoses in ANY auto parts store under ANY brand. However, Corvette Stainless Steel Brakes (CSSB) in Florida has US-manufactured brake hoses.

[Craig J.]

Re: C3 Spomgy brake pedal.

Vette Brakes and Products also carries US-made brake hoses.

[Terry M.]

Re: C3 Spongy brake pedal.

Had front rubber hose collapse inside. Sleeved caliper removed and replaced (front) Bled bakes numerous times with clear heavy flow of fluid. Place foot on pedal still goes to floor slowly with motor operating. This all started with car pulling to right when brake was applied Whats next?

Frank,
For some reason C2 & C3 brake systems are just difficult to properly bleed. I had success using gravity method, followed by the two person final check. Others on this board swear that pressure bleeding is necessary. They recommend the Motive unit:

http://www.summitracing.com/parts/mvp-0100?seid=srese1&gclid=CKampKHon74CFYtAMgodIzwAIw

I am not recommending that supplier necessarily, it was the first image that came up on Google. If you are using poly-glycol brake fluid (DOT 3, 4, or 5.1) I would suggest you use only the air pressure from this unit and not put brake fluid in it. One of its failure modes is for the master cylinder cover to come off under pressure. Your car does not need a spray bath with this type of brake fluid. Of course follow manufacturer's recommendations regarding the pressure applied to the system. I am a fan of DOT 5, but that is another story, and discussion for another time.

[Michael F.]

Re: C3 Spongy brake pedal.

I use dot 5 in my 67 with success since the early 90s

[Duke W.]

Re: C3 Spongy brake pedal.

Had front rubber hose collapse inside. Sleeved caliper removed and replaced (front) Bled bakes numerous times with clear heavy flow of fluid. Place foot on pedal still goes to floor slowly with motor operating. This all started with car pulling to right when brake was applied Whats next?

This could indicate an internal master cylinder failure to hold pressure, however, it's usually only one side, which would cause the differential pressure switch to light the brake warning light. If both sides won't hold pressure due to internal failure then the light won't illuminate. In either case there is usually no external leak. If there is an external leak the reservoir level(s) will be down with multiple pedal applications.

If an internal master cylinder problem, the brake should go to the floor or near the floor with the engine off or on, but if off it will take more pedal effort assuming you have power brakes.

Make sure that the bottom of the reservoirs are squeaky clean and the tiny compensating ports are not clogged.

Sludge buildup at the bottom of the reservoirs along with corrosion over the years due to lack of periodic flushing is a common cause of brake failure.

Duke

[Daniel S.]

Re: C3 Spongy brake pedal.

Just went through this. Had to rebuild one front caliper. Used 2 person method and Mity Vac suction method. Both did nothing but waste fresh brake fluid. Forked over the $70 for the Motive pressure bleeder with master cylinder adapter and had hard pedal within an hour.

[Richard M.]

Re: C3 Spongy brake pedal.

You may want to consider a total brake overhaul, including all hoses, wheel calipers and master cylinder. Do a thorough flush of the system and bleed.......

This could indicate an internal master cylinder failure to hold pressure, however, it's usually only one side, which would cause the differential pressure switch to light the brake warning light. If both sides won't hold pressure due to internal failure then the light won't illuminate. In either case there is usually no external leak. If there is an external leak the reservoir level(s) will be down with multiple pedal applications.

If an internal master cylinder problem, the brake should go to the floor or near the floor with the engine off or on, but if off it will take more pedal effort assuming you have power brakes.

Make sure that the bottom of the reservoirs are squeaky clean and the tiny compensating ports are not clogged.

Sludge buildup at the bottom of the reservoirs along with corrosion over the years due to lack of periodic flushing is a common cause of brake failure.

Duke

Frank,

Agree with these suggestions....... Because this exact scenario just happened to me last week on a friend's '72. We replaced all 4 hoses as a safety, flushed the entire system of dirty DOT 3 fluid, and did a foot on the pedal bleed. Did the rears, fine. Went to the fronts, totally lost the pedal after about 4 cycles of bleeding. The differential switch never turned the light on as I suspect there was never any pressure going out of the MC.

The master cylinder failed. We replaced it, re-bled everything again and all was fine.

I suspect the internal seals caught a bridge in the bore of the cylinder and tore, thus causing a bypass condition inside the bore. The foot bleeding makes the MC piston and seals go places that they've never been until they were new.

Rich

[Duke W.]

Re: C3 Spongy brake pedal.

Frank,

I suspect the internal seals caught a bridge in the bore of the cylinder and tore, thus causing a bypass condition inside the bore. The foot bleeding makes the MC piston and seals go places that they've never been until they were new.

Rich

Years ago a buddy of mine bought an old Porsche 914. The brake fluid looked like week old coffee, and the corrosion gremlins had probably been at work for years. So I suggested he have the system flushed, but his "mechanic" recommended against the procedure for the reason you cited above.

My take was that it is better to have the m/c fail in the shop rather than on the road... anyway, he didn't flush the system, but sold the car within a couple of years, and the brake system was still okay.

I have no doubt that there are a lot of vintage cars out there with an inicipient brake system failure right around the corner.

Duke

[Patrick H.]

Re: C3 Spongy brake pedal.

Just went through this. Had to rebuild one front caliper. Used 2 person method and Mity Vac suction method. Both did nothing but waste fresh brake fluid. Forked over the $70 for the Motive pressure bleeder with master cylinder adapter and had hard pedal within an hour.

You've got me beat. I've never done any better with the Motive than any other method, and the Motive seems to be excellent at spilling brake fluid everywhere OR pushing the fluid out of the system and leaving one of the bowls dry. Several uses later I figure that there must be an art to using one, but I'm not an artist.

[Joe L.]

Re: C3 Spongy brake pedal.

You've got me beat. I've never done any better with the Motive than any other method, and the Motive seems to be excellent at spilling brake fluid everywhere OR pushing the fluid out of the system and leaving one of the bowls dry. Several uses later I figure that there must be an art to using one, but I'm not an artist.

Patrick------


The "Achille's Heel" of the Motive bleeder is the master cylinder adapter retained by "chains". This is TOTALLY inadequate, to say the least. A modified or improvised adapter is the solution.

[Patrick H.]

Re: C3 Spongy brake pedal.

Patrick------


The "Achille's Heel" of the Motive bleeder is the master cylinder adapter retained by "chains". This is TOTALLY inadequate, to say the least. A modified or improvised adapter is the solution.

Oh, I've done that. The problem is that once you get to the point where you've got air and not fluid in the line from the bottle to the MC, when have you removed enough to to spill out once you remove the adapter?
There is no way to know, and it's way too easy to not remove enough and then have it spill once you remove the adapter plate.