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Louisd75
Samba Member
Joined: October 01, 2006
Posts: 21
Location: Bellingham WA
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 Posted: Sun Nov 12, 2006 12:12 am Post subject: Brakes |
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I've been having problems with my brakes since purchasing my 1970 bus last summer, most notably a slight pull to the left under hard braking, and sponginess in the pedal which sometimes necessitates pumping the pedal a couple of times. I've lived with it so far because it was just part of driving the bus. Recently, the brakes have gone downhill pretty quick and it just isn't fun anymore, so I'm trying to do something about it. In addition to pulling, there have been two instances where the front brakes didn't seem to do anything while the back brakes locked up. Both instances involved a slight downhill. In addition, the brake fluid reservoir would drop 1/4 to 1/2 an inch per week, depending on how often I was driving.
I ordered new brake shoes and started taking things apart. The front right drum had a nice little pool of brake fluid in it and the top wheel cylinder was leaking. That explains the bus pulling to the right. Being a college student and not exactly rolling in cash, I ordered rebuild kits from Busdepot for each cylinder in the front wheels. In the meantime, I cleaned everything up and replaced the rubber grommet that seals the master cylinder reservoir to the filling tube that runs up to the small reservoir inside the bus.
The rebuild kits arrived and there was much rejoicing. I removed the cylinders from each wheel, cleaned them really well and installed the new rubber ring and seal. I installed the new shoes and put the drums back on. I bled the front brakes (at the time I didn't have the right size wrench for the rear brakes) and it looked as though I removed a lot of air from the system, which I was expecting considering that I had opened everything up. No matter how much bleeding we did, we could not get the pedal to feel solid. After a trip for the right wrench, we bled the rear brakes. No air came out. So we bled the front brakes again. A little air came out of the driver's side, but nothing from the passenger side. The brakes still did not feel right at the pedal. If you pump them, eventually you'll get a solid feeling, but if you don't pump them, the pedal goes straight to the floor. I've checked every connection that I so much as looked at during this job, they are all tight and I see no leaks. I pulled the drums back off to see if there was any leaking from the wheel cylinders, but could find none. I left the bus sitting over two nights and the brake fluid level did not change in the reservoir.
I drove the bus tonite and found that the brakes work great if you have time to pump them five times before you need them, otherwise the pedal goes straight to the floor.
One other detail I should mention. If I pump the brakes a few times, the I can get the brakes to feel solid so long as I keep pressure on the pedal. If I ease up just a tiny amount and then reapply the pressure, the pedal goes straight to the floor.
I'm running out of ideas now. I'm pretty sure that there is still air in the system, but I don't know where it could be that it wouldn't come out during the bleedings. I've wondered about the master cylinder, but the rear brakes were working well enough to lock up and the front brakes would work with a couple of pumps, although on tonite's test drive I couldn't get any of the brakes to do anything.
Any ideas?
Louis
1/C ME cadet
3A/E in training |
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67jason
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Joined: August 28, 2005
Posts: 4741
Location: behind my back feet - Pittsburg CA
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| Posted: Sun Nov 12, 2006 12:43 am Post subject: |
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did you adjust all the brakes before bleeding?
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Louisd75
Samba Member
Joined: October 01, 2006
Posts: 21
Location: Bellingham WA
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| Posted: Sun Nov 12, 2006 12:54 am Post subject: |
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I haven't done anything with the rear brakes except look at the pad thickness through the hole in the drum and then bleed the brakes.
The front brakes I adjusted per Muir's book, by tightening adjusting both stars evenly until the shoes hit the drum, and then backing off til the drum spun.
Louis
1/C ME cadet
3 A/E in training |
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67jason
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Joined: August 28, 2005
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Location: behind my back feet - Pittsburg CA
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| Posted: Sun Nov 12, 2006 12:56 am Post subject: |
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try adjusting the rears then bleed again. also what kind of shape is your rubber brake hoses in? they can cause problems if they are collapsed on the inside.
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vdubyah73
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Joined: July 05, 2003
Posts: 2541
Location: somewhere in Texas, my house has wheels
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| Posted: Sun Nov 12, 2006 4:59 am Post subject: Re: Brakes |
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| Louisd75 wrote: |
| the brake fluid reservoir would drop 1/4 to 1/2 an inch per week, depending on how often I was driving. |
You have / had a leak somewhere.
| Louisd75 wrote: |
| One other detail I should mention. If I pump the brakes a few times, the I can get the brakes to feel solid so long as I keep pressure on the pedal. If I ease up just a tiny amount and then reapply the pressure, the pedal goes straight to the floor. |
I'd think master cylinder, they can leak internally and externally.
Bill
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atmellovw
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Joined: September 05, 2006
Posts: 1652
Location: Minnesota
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| Posted: Sun Nov 12, 2006 6:08 am Post subject: |
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Did you bleed the brakes in the proper order? Farthest from master cylinder first and so on...
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cbcarch
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Joined: November 03, 2006
Posts: 224
Location: St. Louis, MO
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| Posted: Sun Nov 12, 2006 9:56 am Post subject: bus brakes |
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I'd suspect the master cylinder as well.
Also, did you bleed the brakes the traditional way, with a helper pumping the pedal while you watch the bubbles go away and then tighten the bleeder valve? If so, you should also get a professional grade
vacuum/canister type bleeder/evacuator--the shop manual actually recommends this method. You will get ALL of the air out. Then you can better diagnose where the trouble is.
hope you get 'em solid.
I'm getting ready to replace all my rears today.
Cheers!
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Louisd75
Samba Member
Joined: October 01, 2006
Posts: 21
Location: Bellingham WA
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| Posted: Sun Nov 12, 2006 11:57 am Post subject: |
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| 67jason wrote: |
| try adjusting the rears then bleed again. also what kind of shape is your rubber brake hoses in? they can cause problems if they are collapsed on the inside. |
The rubber hoses *look* ok from the outside. I don't know what they're supposed to feel like, ie soft and pliant or hard and not flexible, but they're somewhere in between.
[quote="vdubyah73] I'd think master cylinder, they can leak internally and externally.[/quote]
I was kind of hoping that this wouldn't be the case, but I figured it'd be a likely suspect after I finally got the rubber grommet between the master cylinder reservoir and filling tube installed. Guess I'll get to do that twice, eh?
| cbcarch wrote: |
| Also, did you bleed the brakes the traditional way, with a helper pumping the pedal while you watch the bubbles go away and then tighten the bleeder valve? If so, you should also get a professional grade vacuum/canister type bleeder/evacuator--the shop manual actually recommends this method. You will get ALL of the air out. Then you can better diagnose where the trouble is. |
I did bleed the brakes with a helper, starting at the right rear, then the left rear, right front, left front. I spoke with a friend last night and he'll be bringing a bleeder to school when he comes back from the long weekend. It might be a few days before I'm able to get to it again since all of our instructors seem to pick the same week to have all of our projects/writing assignments/labs due.
If it is the master cylinder, are there any recomendations as far as rebuilding/replacing? It looks like a straightfoward removal and installation from the outside, all of the connections appear to be in good shape.
Thanks for all of your help and suggestions.
Louis
1/C ME cadet
3 A/E in training |
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Randy in Maine
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Joined: August 03, 2003
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Location: The Beach
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kevlore
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Joined: September 21, 2006
Posts: 46
Location: Moving to Bend, OR March 10th!
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| Posted: Mon Nov 13, 2006 9:49 pm Post subject: |
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Yep, what Randy said.
Most hoses are dated. My bus was pulling to the left and my right front would stick occaisionally. i replaced all the hoses and now she stops straight and quick.
The date on my hoses? 72, they were original!
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Louisd75
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Joined: October 01, 2006
Posts: 21
Location: Bellingham WA
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| Posted: Tue Nov 14, 2006 12:41 pm Post subject: |
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I've new hoses and master cylinder on the way. I tried finding the steel braided hoses for the 1970 model year, but could only find them for the rear brakes. Has anyone seen them for the front? In the meantime, I've got rubber replacements on the way that should last me til I graduate in April and start making the big $$.
Louis
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galexander
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Joined: April 17, 2003
Posts: 610
Location: Round Rock, TX
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| Posted: Wed Nov 15, 2006 10:47 am Post subject: |
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I just went through a similar scenario as yours on my '66 bus. And now, I cannot believe how good a pedal I have and how true it stops , no dragging to the left or right.
In order of how it worked out for me:
1. replace all 4 rubber brake hoses, front and rear
2. replaced wheel cylinders, inlcuding the the pair in each front wheel
2b, replaced brake shoes, front and rear
3. raised bus on jack stands(4) and adjusted each brake shoe per Muir.
4. filled Motive Brake pressure bleeder with brake fluid, then attached cap to the brake reservoir, pumpd up to about 15psi, and cracked open bleeder on RR, then LR then LF and finally RF.
5. Then I still had a long pedal, it was solid, just a 3/4 way till it got there, so I adjusted the brake master cylinder push rod(per Muir again, man that book is fantastic) and wow, now it stops great with a nice high pedal.
Good luck,
Gary
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Louisd75
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Joined: October 01, 2006
Posts: 21
Location: Bellingham WA
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| Posted: Wed Nov 15, 2006 9:15 pm Post subject: |
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| galexander wrote: |
I just went through a similar scenario as yours on my '66 bus. And now, I cannot believe how good a pedal I have and how true it stops , no dragging to the left or right.
In order of how it worked out for me:
1. replace all 4 rubber brake hoses, front and rear
2. replaced wheel cylinders, inlcuding the the pair in each front wheel
2b, replaced brake shoes, front and rear
3. raised bus on jack stands(4) and adjusted each brake shoe per Muir.
4. filled Motive Brake pressure bleeder with brake fluid, then attached cap to the brake reservoir, pumpd up to about 15psi, and cracked open bleeder on RR, then LR then LF and finally RF.
5. Then I still had a long pedal, it was solid, just a 3/4 way till it got there, so I adjusted the brake master cylinder push rod(per Muir again, man that book is fantastic) and wow, now it stops great with a nice high pedal.
Good luck,
Gary |
Sounds kind of like what I'm shooting for. Turns out the parts I ordered were out of stock. I'm a bit bummed since I was hoping to be able to put them on for this weekend, but now I'm just trying to get it driveable. I've got next week off for Thanksgiving, and I know that there's a shop that has the parts close to where I'm staying, I just have to get there. I borrowed a vacuum bleeder from a friend, and I've noticed a huge improvement using just that. I'm just using it for vacuum, though I think with a little creativity I could use it as a pressure bleeder. My only concerns are that my brake fluid reservoir in the cab has a couple of lines on it that look suspiciously like cracks. No fluid comes out of them, but I'm leary of putting any sort of pressure into the system from there. The only other way that I can think of would be to remove the fill hose and rig some kind of adapter to pressurize the reservoir that sits directly on top of the master cylinder. This might be doable, but then I run into the problem where the brake bleeder reservoir is relatively small, about the same size as the cab fill reservoir, so I could see myself easily sucking air into the system if I wasn't *really* careful. The pedal already feels firmer than ever before, but it still goes to the floor. I'm not sure that I've gotten all of the air out of the right rear yet, but I've got confidence that I'll have it roadworthy by the weekend. I'm using the Muir book too, and I agree, it's pretty much the best.
One thing that I found out on accident, when I was still driving the bus and the brakes were dodgy, was that I was "bleeding" the system every time I went over to a friend's house to do homework. The hill outside of his house is really steep, and I found that if I parked the bus on the street with the nose uphill, the air bubbles naturally worked their way out of the system through the reservoir in the cab.
Louis
1/C ME cadet
3rd A/E in training |
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