spongy brake pedal and tons of air in the lines...

[G50911]

i always knew my brake pedal was a little spongy and a couple days ago i decided to change out pads and rotors. after i was told "damn your brakes are soft" i decided to tackle bleeding it.

i used a vacuum pump to pull the air out of the lines (started from the passenger rear) and found air bubbles to no end. i mean NO END. the size of the bubbles were huge too. i checked all the lines and couldn't find any leaks in the system. master cylinder looked fine and no seepage anywhere.

my pump reservoir filled up almost twice and i just gave up. FWIW the bubbles didn't get any smaller and i had no confidence it was ever going to. i made sure the master cylinder reservoir was at or near max the entire time.

anyone encounter this? can the lines have that much air?

[Spumato]

What is the age of the car itself? How long has it been since its been changed? When was it last used?

[DRACO A5OG]

It could be seeping thru the pistons. When was the last time the caliper seals were rebuilt?



3 out of 4 front pistons were pitted and allowing air into my system. No amount of bleeding helped. Swapped - Hard Brakes

[RedCoupe]

I used to use a hand vacuum pump to bleed my brakes, but I switched to the power bleeder that they sell here at Pelican a couple of years ago. With the vacuum pump I always got some bubbles in the fluid coming out because of air being sucked around the bleeder screw threads, but with the power bleeder you don't have that problem and can see when the air bubbles are gone. In the instructions for the vacuum pump it said to wrap the bleeder screw threads with Teflon tape, but I didn't really like that idea so I just bought the other style bleeder. IMO I think bleeding with pressure gets the air out of the master cylinder better than sucking it through with vacuum.

[DRACO A5OG]

Go old sckool and do a two man pump to make sure.

Remember to place a block of 2X4 behind the pedal as not to damage the MC while pumping to the floor.

Remember 1/4 turn on the nipple, no more. Use some di-electric grease around the nipples to insure air tight seal or use a zip tie.

[heimtun]

Spongy brakes aside. +1 Vacuum bleeding can get lots of air from the bleeder screw threads.
I'd go with previous suggestion of pressure bleed or the two person method - a good way to get your significant other involved. YMMV

[G50911]

it's a 68. i've driven it spiritedly on weekends and did some track time. i've noticed it to be a little soft but i just got used to it. i figure since i did the pads and rotors i may as well flush and bleed them.

the calipers look very clean. at least they don't look to be untouched since 68 so I'm guessing it could have been rebuilt at some point. i thought about air coming thru the threads but wouldn't the bubbles be super tiny? especially since i've tried cracking it just a bit and then 1/4 turn and then 1/2 turn. there's no change in bubble size when i do this. i guess i'll try gravity bleeding and old school pumping too.

damn i got up early too sort the brakes so i can do a quick run this morning. now it's turning into an all day thing. (!&#^$%)

[sugarwood]

Originally Posted by RedCoupe

With the vacuum pump I always got some bubbles in the fluid coming out because of air being sucked around the bleeder screw threads, but with the power bleeder you don't have that problem and can see when the air bubbles are gone.

+1. Vacuum pump is garbage. It was creating an endless stream of air bubbles, b/c the connection at the nipple was crap. Wasted an entire bottle of fluid and a few hours until I said screw this. I'll wait for a helper who can pump the brake pedal, old school.

[sugarwood]

Originally Posted by G50911

damn i got up early too sort the brakes so i can do a quick run this morning. now it's turning into an all day thing. (!&#^$%)

I never schedule plans after a car project.
One hour job quickly turns into 5.

[Bob Kontak]

Originally Posted by G50911

i thought about air coming thru the threads but wouldn't the bubbles be super tiny?

Red Coupe is correct. Vacuum bleeding will create any size bubble that can bleed around the hose. Big or little. It's just physics and suspect this is your issue.

You would also not pull bubbles if you had that much air in the system. You would pull packets of air.

If you have no friends or significant other like me, here is what I suggest to maybe save the day.

Get to the parts store and buy some one way bleeders. They pinch, $10 or so for two.

Disconnect the lines from the master cylinder and bleed both (with one way bleeders) into a plastic bag. Spits the fluid right out the side of the master cylinder. Zip tie, rubber band, whatever on the bag to keep it off your paint.

Reconnect the lines to the bled master cylinder. Put the two new bleeders in the rear and go to town then move to front.

I am not sure what size goes where, front, rear, master cylinder but you can take your bleeders in and match them up.

This will work if your system has integrity. Betting master cylinder has a nice lump of air in it.

[Bob Kontak]

Originally Posted by sugarwood

I never schedule plans after a car project.
One hour job quickly turns into 5.

That is just silly. None of us true DIY professionals ever have that happen to us.

You are just trying to make him feel good.

[DRACO A5OG]

��

[JohnJL]

How did the pedal feel after the bleed. As above, a vacuum bleeder is prone to showing lots of air which can come in not only from actual air in the lines but from the bleeder nipple/hose connection and through the bleeder threads.
I have a those pressure bleaders too but I acutally have gone back to the good ole fashioned "pumpem and fillit" routine with better results/less liklihood of spillage/wastage.

[Bob Kontak]

Originally Posted by JohnJL

I have a those pressure bleaders too but I acutally have gone back to the good ole fashioned "pumpem and fillit" routine with better results/less liklihood of spillage/wastage.

All methods work pretty well but if MC has air or is tired, you can pull your hair out.

I do like the old fashioned method as well. Pal with a big foot that listens while you bark.

Believe a hint the MC is the culprit is if you can pump multiple times and pedal gets stiffer.

[G50911]

i just got abducted by a 6 pack of beer and a hot tub... going to try out the old school method later tonight. btw, the rear has 2 bleed plugs. i should be bleeding from the inside out right?

[reddogmotrsprts]

Yes, bleed each caliper from the inside out. We use the shop-air-to-reservoir adapter ($15 or so) when we have to bleed brakes solo, but we have the best results from the two-man process. If you use the pressure method, try not to put more than 15-20psi to the reservoir. We use a valve to prevent any splashing of fluid when we remove the cap, and this allows us to bleed the pressure out of the reservoir before pulling the cap off to top off the fluid.

We setup a mirror above the reservoir. We dial it in using a laser thermometer so that the guy pumping the pedal can keep an eye on the reservoir fluid level. This saves some back and forth checking and topping-off and is especially useful when bleeding a car from which you previously have removed all the brake fluid.

More than you needed to know about this process, I'm sure.