Bled new Wilwood brakes but still spongy pedal

[wabco40]

Yes, thinking the same mate. Pressure bleeders are damn expensive though for 1 job. Got a mechanic coming out this afternoon, so will see how we go.

I can't remember how much it cost but I don't think it was that much. It gets used often enough (not just on the Vette) to justify it.

You could make one easy enough. When I use the pressure bleeder I don't put any brake fluid in the pressure tank. I just keep the master cylinder topped up. I clamp the top plate onto the master cylinder and then pump 10 psi into the tank.
10 psi head pressure on the MC is more then enough to force any air out of the system. It's then just a matter of opening the nipples in order to bleed. Because I don't put fluid in the bleeder tank, after each caliper I release the air pressure and remove the top plate off the MC to top it up with fluid again.

A cheap garden sprayer from Bunnings, a flat steel plate (with a rubber gasket) clamped to the top of the master cylinder and a nipple on the plate to join the hose from the sprayer will do the same thing.

[bfit]

I've seem a how to on a us forum to make one of these out of a weed sprayer .
Google it

[jimandemma]

no luck with mechanic, pressure bleeder next

[wabco40]

It's not fancy but it's cheap.

Doesn't need a gauge as 10 psi is only about ten pumps. The master cylinder top plate can just be a flat steel plate held on with a large G clamp.

https://www.corvetteforum.com/forums/c3-general/2905428-homemade-motive-type-power-bleeder-for-14-a.html

[gtc]

^ The last time my Vette brakes were bled, that sort of bleed device was used.

[bfit]

This is the one I'd make it out of

http://www.hardwareshoptoyou.com/h2u-ebay_wordpress/wp-content/uploads/2017/05/FireShot-Capture-51-Hardware-To-You_-http___www.hardwareshoptoyou.com_h-e1494652679631.png


When your finished use it I'm the garden

[jimandemma]

Got a brake specialist coming out Thursday, so will keep you guys in the loop.

[bfit]

I have seen the brakes on a vette test the best of mechanic's.

[bfit]

How did it go

[jimandemma]

He never turned up! Had to re-book for Tuesday. In the meantime, I tried forcing fluid through the bottom nipples to the top with an oil can and hose. Got some bubbles out, but the oil can died. Getting another today and will continue. Pedal still the same though.

[bfit]

I get very very p==sed off when tradesman don't turn up .

[gtc]

I get very very p==sed off when tradesman don't turn up .

Who doesn't?

And to not take the trouble to call and reschedule simply says that we don't matter.

[jimandemma]

Brake guy came out this afternoon. Clamped the lines and still a soft pedal, engine off. He checked the system and with clamps off, everything working, calipers moving front and rear. He believes it could be the proportioning valve, if not, master cylinder but 9/10 the valve. I pulled the master cylinder last night to check for leaks, nothing. So the question is, could it be the valve and if so, where to get one here in Australia or NSW?
No brake light is showing on the dash.

[bfit]

Ponti world  tel:02 4257 1230

[jimandemma]

Thanks Bfit. What do you think, the valve maybe?

[wabco40]

Did he use a pressure bleeder?

I've been through the same thing thinking it's the valve, master cylinder etc.

The problem with C3 brakes is there are too many places for air to get trapped.

I had the same problem with standard calipers as with Wilwood calipers.

10 psi of head pressure on the MC sorts out the problem.

[jimandemma]

No pressure bleeder mate, it all comes back to that though doesn't it. I"m going to buy one and try it first I think. Problem is, where in Australia do you get one???

[wabco40]

Just make one as stated in a previous post.

Garden sprayer and a flat plate to clamp onto the MC.

The plate can be a piece of steel, aluminium or maybe even wood. Just use a thin sheet of rubber as a gasket between the plate and MC. Hold it in place with a large G clamp. Then join the hose from the garden spray to a nipple on top of the plate. The nipple does not have to protrude into the reservoirs. You only need to be able to seal air pressure between the top of the fluid and the flat plate.
About 10 pumps of the sprayer should be enough for sufficient head pressure. Just keep a eye on the fluid level and don't let it run dry.

I will see if I have any pictures I can post.

[bfit]

Thanks Bfit. What do you think, the valve maybe?

I have read that the proportioning valve can cause these sort of problem , I personally can't see how.
I have not striped a valve out of a 75 model , I'm familiar with the earlier models.
Which control rear whell pressure with what I would call a modulation valve.
The spool moves to restrict the port area to the rear hence reducing the pressure.
I'm thinking do you have any line pressure valves fitted ,  your original calipers should have springs behind the pistons to keep the pads out .
If you have no line valve to hold residual pressure in the lines , then that can cause this problem.
What I don't get , if I read your post correctly .
With the line clamps , soft pedal  yes
Removed clamps and hard  pedal . If that's right  it is odd to say the least.
I have to say I do not agree with clamping brake lines.

Now when I had wilwood calipers I did not have line valves, I always had to two tap the brakes the get a full pedal

[jimandemma]

Pedal feel is the same with or without clamps