Bleeding Brakes

[Dave Forster]

This may be a dumb question, but I'm having trouble bleeding the brakes.

The car has the stock Tilton Series 600 pedal set that came with the kit. Using a pressure bleeder combined with the traditional pedal pumping and nipple valve cycling, we got the pedal rock hard (yaay!), but by the time the car had rolled out to the driveway, it was feeling soft again and by the time I got to the end of the street, it required pumping to come to a stop.

Yes, this means the car is now officially at the go-kart stage (another yaay!)

We tried bleeding again using the same method and didn't see any air bubbles, but once again after the bleeding process, the pedal felt hard and then a short while later, felt soft again.

At no time could we find any brake fluid dripping from any of the brake line connections or under the master cylinders.

I'm wondering if this means I have bad seals in the Tilton master cylinders? What do you guys think?

 

[PeteB]

It takes a lot of bleeding to get all the air out of new, empty lines. I had the same issue as you describe when I built my Cobra. This time I used a reverse pressure bleeder: V5 DIY Reverse Brake Bleeder - Phoenix Systems. I still had to bleed a little using the traditional method, but I had good brakes on the first drive.

 

[Howard Jones]

Wait a few days and re bleed. It takes a few times to get all the little bubbles to group up, I think. If after several try's they won't stop getting soft you may have a bad master seal but I wouldn't take things apart yet.

Patience grass hopper. You will get it. We all do in the end.

 

[John]

Also, did you bench bleed the master cylinders?

 

[Bill]

The brakelines are stainless steel vs the more typical bronze. The SS line connections can be a bear to get sealed. Have you seen any leaks?

 

[Mike]

The brakelines are stainless steel vs the more typical bronze. The SS line connections can be a bear to get sealed. Have you seen any leaks?

Yea, what Bill said. These connections must be tight - you're deforming/mating metal to get a good seal. May a connection be tight enough to not casually drip fluid, but still allow air to get by and in the line?

BTW: I have a power bleeder and have never found it to be as good as the old fashioned two person/pump pedal method.

 

[Scott Davis]

If you didn't bench bleed, you may want to reverse or vacuum bleed using one method or another like Pete mentioned (can use pump up garden sprayer). Sometimes it hard to get enough pressure from the two person method to get air out before it rises back again. And if enough air, pumping rapidly can foam and make more difficult to push air out and then as suggested a couple days break may help.

 

[Dave Forster]

Thanks for all the tips.

I didn't bench bleed the master cylinders, but have up to now tried pressure bleeding from the reservoir, reverse pressure bleeding and vacuum bleeding from the calipers. The best results have been the latest ones, by pressure bleeding from the reservoir while doing the up/down pedal, nipple open/closed thing.

I will try a couple of times again over the next few days and see what happens. It never occurred to me that it might take an extended wait between bleeding attempts for things to settle out - or that we might get foaming by pressing too quickly on the pedal. . .

 

As I understand it, the pedal gets hard after repeated pumping, but softens when inactive. I'm of the mind that says that it is the main seal in the master cylinder which relaxes back to it's inactive position gained when it was sat on the shelf for months before the build. You've got the air out, you've got no leaks, so the fluid must be bypassing the master cylinder seal imho. Let us know what you find, Tony.

 

[Scott Davis]

Wow...you put in some work. Not to state the obvious and I'm not sure this is capable on your setup, but sometimes its possible to have the calipers switched (pass on driver). Nipple up typically.

 

[Cam]

This may be 5 year old, stale information but i remember there was a joint in the rear brake line in the chase by the drivers side door. it was a real pain to get at to finally seal. I remember buying a line wrench and having to cut a few inches off to be able to get it to fully tighten. Are you using line wrenches?

 

[Dave Forster]

Yes, I am using brake line wrenches. Pretty sure non the of the joints are leaking - they are consistently dry to the touch. The bleed nipples on all the calipers are at the top of the caliper (inlets on bottom).

The last bleeding session seemed to help a bit. I will try another and see what happens, though I didn't see any bubbles come out of the line on last try.

I'm also suspicious of the seals in the master cylinder.

 

[Howard Jones]

Try this Dave. When you are depressing and releasing the brake peddle do it slowly. Lets say take 3-4 sec to go all the way it and about the same time to let out. I'm not sure why this helps but it does.

 

[Pat Buckley]

I think the reason that's a great idea is because thrashing away at the brake pedal could cause cavitation? Just a guess, but probably a good one.