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TomWesty
Samba Member
Joined: November 23, 2007
Posts: 3529
Location: Wyoming,USA
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 Posted: Thu May 25, 2017 5:39 pm Post subject: '71 brake servo and master cylinder replacement |
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I figured I would do a brain dump of what parts I used and anything I think might help. The first thing I did was review the harveybacon video on YouTube.
I bought all parts at EIS because they had everything I needed in one place.
Airtec brake servo for '71 bus ( set the actuator rod the same length as the one on your old servo. You'll need 7mm and 8mm wrenches to do it.) I believe it was Kreemoweet who discovered that. Correct me if I'm wrong....
Master cylinder part number 211611021AA ( it came with the reservoir grommets already in it so I really didn't need to purchase those.)
Airtec lower reservoir part number 211611313J and associated sleeve to go in side the tube from the upper reservoir. I discovered my brake switch boots were shot and found that EIS also has the correct ones, but I can't figure out how you could install them without destroying them.....part number 211945521A. You need a 24 mm socket to remove the switches. You need a 19 mm wrench and maybe a big Crescent wrench to remove the brake pedal rod from the front of the servo. After all was replaced I got a quart of brake fluid and tried using a Mightyvac to bleed the brakes. It didn't work that well for me so I reverted to the Bentley procedure and it worked fine. I also replaced the vacuum lines with 15/32" Gates vac line part number 27231. I now have power brakes again! My right hip and knee have already thanked me. Also, thanks to Aeromech (Gary) and Busdaddy for their brakes posts over the years.
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airschooled
Air-Schooled
Joined: April 04, 2012
Posts: 13521
Location: West Coast, USA
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| Posted: Thu May 25, 2017 5:44 pm Post subject: Re: '71 brake servo and master cylinder replacement |
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Glad you got it working, Tom!
I've also had minimal success vacuum bleeding a pressure system, but when Aeromech did it on my bus years ago the pedal was FIRM. I probably just missed a step or two, but 'ye olde up down' method hasn't failed me yet……
Was your MC bad, or did you just feel like replacing it?
Robbie
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TomWesty
Samba Member
Joined: November 23, 2007
Posts: 3529
Location: Wyoming,USA
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| Posted: Thu May 25, 2017 5:56 pm Post subject: Re: '71 brake servo and master cylinder replacement |
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| asiab3 wrote: |
Glad you got it working, Tom!
I've also had minimal success vacuum bleeding a pressure system, but when Aeromech did it on my bus years ago the pedal was FIRM. I probably just missed a step or two, but 'ye olde up down' method hasn't failed me yet……
Was your MC bad, or did you just feel like replacing it?
Robbie |
Let me put it this way, I set the old servo on the ground with the vac port down and black brake fluid poured out all over the place. 
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airschooled
Air-Schooled
Joined: April 04, 2012
Posts: 13521
Location: West Coast, USA
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| Posted: Thu May 25, 2017 6:05 pm Post subject: Re: '71 brake servo and master cylinder replacement |
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| TomWesty wrote: |
| asiab3 wrote: |
Glad you got it working, Tom!
I've also had minimal success vacuum bleeding a pressure system, but when Aeromech did it on my bus years ago the pedal was FIRM. I probably just missed a step or two, but 'ye olde up down' method hasn't failed me yet……
Was your MC bad, or did you just feel like replacing it?
Robbie |
Let me put it this way, I set the old servo on the ground with the vac port down and black brake fluid poured out all over the place. |
Ouch. I was going to say, for the readership, that it is possible to replace the booster without removing hydraulic components, but I think you needed a "little" bit more than that. 
Robbie
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aeromech
Samba Member
Joined: January 24, 2006
Posts: 17660
Location: San Diego, California
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| Posted: Thu May 25, 2017 7:58 pm Post subject: Re: '71 brake servo and master cylinder replacement |
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Tom,
Yeah with that new booster you have to make a slight adjustment so the pedal has a little bit of free play.
On the boots you'd need to release the female spade connectors from the plastic plug then thread them through the new boot and reinstall.
I have a mityvac. It sucks, not literally, for brake work. I use a Vacula from Sweden. Freaking thing is the bomb. Glad you got it done.
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Boeing 727,737-200-300-400,757,767
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TomWesty
Samba Member
Joined: November 23, 2007
Posts: 3529
Location: Wyoming,USA
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| Posted: Fri May 26, 2017 12:09 am Post subject: Re: '71 brake servo and master cylinder replacement |
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| aeromech wrote: |
Tom,
Yeah with that new booster you have to make a slight adjustment so the pedal has a little bit of free play.
On the boots you'd need to release the female spade connectors from the plastic plug then thread them through the new boot and reinstall.
I have a mityvac. It sucks, not literally, for brake work. I use a Vacula from Sweden. Freaking thing is the bomb. Glad you got it done. |
Yeah, that's what I figured. I looked at the big plug and the tiny hole and knew there would be some level of disassembly involved.
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If you haven't bled on them, you haven't worked on them.
Visit: www.tomcoryell.com and check out my music! |
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TomWesty
Samba Member
Joined: November 23, 2007
Posts: 3529
Location: Wyoming,USA
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| Posted: Wed Jul 02, 2025 10:02 am Post subject: Re: '71 brake servo and master cylinder replacement |
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I’m Back! Looks like my Airtec booster lasted exactly 8 years. Maybe less. I’m going to replace it with the BBT one from CIP1. It looks like it’s made in China.
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