Creaky Sound from Brake Servo

[Whaanga]

I had my brake servo rebuilt last in February of 2020 by a reputable shop in Indiana. It’s been working very well but recently, it’s making a creaking sound when the pedal comes up. It does this with the engine running or not. It functions well and I have confidence in the braking system but this odd sound has me slightly concerned. Has anyone experienced this? What might be the issue here?

Thanks (as always),

Jeff
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Late 1973 Bay w/a transplanted 914 Engine

[Abscate]

THe diaphragm makes a creak when they relax, when new, especially.
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.ssS!

[Whaanga]

Thanks Steve- This rebuild is a year old and the servo functioned silently until a few weeks ago. The bus sat for a month while I sorted out some fuel/carb issues - but of course, it sat all winter during the off-season and didn't make any noises when I got it back on the road.

I made a little video that demonstrates the condition better than my ability to describe it with words.

https://youtu.be/igdX6ejZZB0
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Late 1973 Bay w/a transplanted 914 Engine

[Abscate]

Wait till the seventh decade hits and your joints turn into bubble wrap....


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.ssS!

[skills@eurocarsplus]

did you bother to lube any of the pivot points? return spring coils?

not for a second do i believe the sound in your vid is internal to the booster
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[orwell84]

You left your Geiger counter on.

[aeromech]

Close off the booster vacuum line. Apply the brakes several times. Any change?
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[Whaanga]

[skills@eurocarsplus]

lube the brake pedal cross shaft where it bolts to the frame. actually, take it out and grease it. bit fiddly of a job getting the spring back on.

the coils of the spring need lube too. if you pull the pedal assy out there is a guide "cup" the coils of the return spring ride on. i have seen these break.

beyond lubing everything i would look for something out of place, broken weld somewhere.

if it's internal to your booster i will shit in my hat. very unlikely it is but nothing surprises me anymore
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[aeromech]

I don’t care how you do it but close off the vacuum and see if it still makes noise. On my 1971 I’d just use some needle nose vise grips and squeeze the hose closed. If you have a late model bus you’ll need to remove the hard vacuum line and plug it
_________________
Lead Mechanic: San Diego Air and Space Museum
Licensed Airframe and Powerplant Mechanic
Licensed Pilot (Single engine Land)
Boeing 727,737-200-300-400,757,767
Airbus A319,320,321
DC9/MD80
BAe146
Fokker F28/F100
VW type 1 1962,63,65,69,72
VW Type 2 1971 (3 ea.) 1978, 1969
VW Jetta
VW Passat
Capable of leaping tall buildings in a single bound

[Whaanga]

I made this post a few months ago and after the suggestions here, got underneath to clean snd grease the brake pedal spring and pin. And it seemed to help for a few months.

However, a couple weeks ago the issue returned. The braking ability of the bus is fine and I’m confident in my ability to stop.

Today, I decided to dig further in and removed the pedal assembly, pin, spring, etc. cleaned everything up and then checked the servo. When I removed the boot I was greeted with water coming out. This surprised me - a lot. I didn’t have time to remove the servo but did my best to blow out the water through the fitting. After reassembly, the pedal action was smoother but there is still a creaking sound come from the servo. Is it toast? Seems like the moisture in there caused the spring to get rusty. The retaining ring was secure on the boot so I’m not sure how the water got in there.

I just had the servo rebuilt in the spring of 2020 and I store the bus in the winter and rarely drive it in the rain - but nonetheless, there was water in there.
Perhaps I can access it from the MC side and can see if I can remove any water in the chamber - but not sure if that will do any good.

Here are a couple of photos of what I saw today. Any guidance would be appreciated. Thank You,
Jeff

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Late 1973 Bay w/a transplanted 914 Engine

[airschooled]

Nice find. Have you checked the integrity of your booster vent hose, and its totally rust-and-moisture-free open end?

In the mean time, I’d shoot it with whatever lubricant your booster rebuilder recommends. On my own car I might use wd40, and only enough to quiet things down.

Robbie
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