air in brake lines

[Whaanga]

I have a 1973 bus and recently redid all the brakes (new pads, rotors on front and shoes, springs on back and replaced both e-brake cables). I also replaced the upper reservoir under the seat as it was damaged when I bought the bus last April. The brakes work well but I feel like I have to push the pedal down farther than I would like. I have bled the brake several times and each time there is air in the lines.

There is no fluid leaking from the front calipers nor in the rear wheel cylinders. I did have to top off the reservoir but not because of losing fluid in the system but because the new reservoir's port is smaller in diameter than the original. To make this spigot's outer diameter larger, I made a bushing with electrical tape and noticed that the loss of fluid was seeping through this modified connection. I've done some work on it and it's dry now. There is no evidence of leaking fluid in the master cylinder or in the servo.

When I first got the bus the vacuum line in the front end running from the carb to the servo was damaged so I replaced it. Before it was replaced, there was always a howling sound when I pressed on the pedal. Once this hose was swapped out, the sound went away.

What other places can I check for air leaks?

Thanks, as always.

[KBDDBD]

Other than the obvious places where things come together and rubber hoses. if the rear drums are out of spec, sometimes you will get air in the lines from the pumping action. It says you replaced your shoes, did you mic the drums?

[Whaanga]

I did not replace the drums. They are in good round and quite clean on the inside.

[SGKent]

how many people are there bleeding the brakes? You and a helper? Did you try a power bleeder?
_________________
“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[busdaddy]

Were the rear brakes fully adjusted before bleeding?, how fast were you or your helper pumping the brakes between bleeds?

As for the electrical tape................WTF?, why not just buy the correct part?, you'll really miss your brakes when they are gone. http://www.busdepot.com/211611833c
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[Whaanga]

I have a helper but not a power bleeder. Yes, the brakes were adjusted before bleeding. When you ask how fast, do you mean the interval between pumping or the rate of speed of each pump itself.

Per the tape - I bought the reservoir two times - the first one broke at the spigot (there was leftover plastic from manufacturing inside of spigot blocking the flow and I was clearing it out with a rat tail file). The outer diamater was also too small on this one. I ordered a second one and it also came with the same sized spigot. I was new at all this so I figured this was how they all were. Looks like I was wrong (not the first time).
Bus Daddy, thanks for the link to Bus Depot. I wish I would have know about this a few months ago. I appreciate the help and chastisement.

Thank You

[busdaddy]

[Tom Powell]

Is it true that a bleed screw, if damaged or not tightened down, will leak some fluid as the pedal is depressed and suck in air as the pedal is released, resulting in a loss of fluid, air in the lines, and a spongy pedal?

Aloha
tp

[Whaanga]

No worries Bus Daddy - I get it. I have six children of my own so I understand where you're coming from. My son (who is my bleeding buddy) and I will double check our procedure. I'll make sure he's not pumping too fast. As we go through the process, we always check the reservoir and top it off is necessary. Also, the Bently says to start with the drivers side, right front, right rear, and then left rear. Ratwell says the opposite. I've tried both and seem to get the same results. Any thoughts about this?

On a properly working system what is a normal range of movement for the pedal before the resistance starts? Mine is about 2" (I know the Bently says a clutch pedal should be about 1"). Also, on the front calipers, do you bleed the top or bottom valve (or both?)

Thanks again.

[busdaddy]

On a well adjusted system there shouldn't be more than 1/2"- 1" of movement, maybe a bit more if the engine's running and you have vacuum boost.

Were the parking brake cables hanging loose while you adjusted each wheel far past where it stopped turning until the star wheels wouldn't turn anymore (then back off until the wheel just turns)?
_________________
Rust NEVER sleeps and stock never goes out of style.

Please don't PM technical questions, ask your problem in public so everyone can play along. If you think it's too stupid post it here
Stop dead photo links! Post your photos to The Samba Gallery!

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[Wildthings]

Only doing 2 or 3 pumps and then doing the bleed will keep the amount of entrained down.

It is possible to suck in air past the cup seals in the slave cylinders, when you release the pedal quickly. The solution is to buy new cylinders or at least to rebuild your old ones.

[BayCreamPuff]

[Whaanga]

Thanks for the input. When I adjusted the back brakes, the e brake cables were not hanging loose (to coin a phrase) but they were not tight either. I'll be up early in the morning to readjust the back brakes and bleed the lines again. In the past, I have done each wheel until the air is gone and a little bit of old fluid comes out. Should I go back around a second or even thrird time in each wheel?

I did adjust the brakes until the wheel wouldn't turn and then backed them off. Maybe I was too generous. I have done drum brakes on my other cars over the years but it's been a while.

I ordered the small part from Bus Depot (surprised that an small/light rubber gasket costs $12 to ship).

Thank you for helping me learn and think this through.

[ToolBox]

[Whaanga]

Ok, here's an update. I discomnected the e brake cables, adjusted the back brakes and found that they needed to be tightened up. Knowing that I'm going to install the new rubber I ordered, I did not bleed the brakes but plan to do this work at the same time. I put everything back together and drove to a friend's house about 10 miles away. The brakes responded much better and everything felt great.

However, I could smell that the back brakes were a little hot and then about five miles in, I began to notice a change in the brake response. By the time a I got to my friend's house, the pedal was traveling almost to the floor.

I got out and checked the back wheels and they were pretty hot. We had lunch and we looked at his amazing 57 Jag ( which has completely been restored and winning prizes at car shows). After the brakes/wheels had cooled, I adjusted them and backed the off a little. This was much better but I made the drive home very carefully. Got home safe and got under the car. There is no evidence of fluid leaking anywhere. There is plenty of fluid in the upper reservoir so am not sure what is going on.

How do I trouble shoot this? I guess I should have bled the lines this morning. Where could air be entering the system?
I've attached a few photos of the components of the brakes system.

[Wildthings]

[SGKent]

did you use the top bleeder on the front calipers when you bled the brakes?

Normally I tighten the bleeder each time the pedal goes down. Have them push down moderately slow so nothing tears in the master.

Buses have to be reasonably level when you bleed them. If the nose is low that will make it hard to get air out of the rears.
_________________
“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[Whaanga]

The fluid may have boiled but the brakes did not return to normal function. I was just fortunate with lots of green lights and moderate speeds. I never want to go through this experiece again.

I'm wondering if the master cylander is bad? Perhaps my mistake was not bleedning the brakes this morning after adjusting them. Honestly, they have never been this bad so am wondering what I did wrong.

Will wait for the new gromet to be placed on the reservoir and then bleed again.

[Wildthings]

Maybe I missed it but are you getting air out of just the rear, just the front, or both?

[Whaanga]

Getting air in front and back brakes.