Itinerant Air-Cooled

Boxcar wrote: While my 9550 cam might be a source of inherently low vacuum#s...booster exhibits a sink soflty to its bottom on pedal's last cms of movement..all the while braking, but requiring faith as progressive resistance of line pressure goes away..almost as if bleeding a cyl.
Thanks.// Eric

And thank YOU for another magnificent haiku/tone poem/word salad.

I shall interpret for the Earthlings, with your blessing . . .

"My performance cam reduces vacuum assist to the booster. I experience a dropping pedal under braking."

To which I get to reply,
"A booster leak/insufficiency exhibits a *rising* pedal, a sinking pedal suggests that your master cylinder is failing or you have a leak elsewhere in the system."
Check for wet spots at the backing plates or for paint blistering/lifting off the booster underneath the master cylinder. If it is the rear piston/seal of the master cylinder, you might also have brake fluid inside the booster can. Check."
Colin

Yep. What you said. After a haikuwordsalad sample.
Sorry, I write it like I feel it.
Hope it breaks the monotony of the successfully expressive postings here.

"A dropping pedal under braking" succinct. Thats it.

Brakefluid not lost.

When I get out of frozen maintenance February, I will again try bumping trans selector into N and opening throttle to boost vacuum assist under braking.It did change pedal drop iirc.

So, dropping pedal under braking is not a symptom of booster demise?

Hieroglyphically yours,happily driving over and under salt encrusted 944. with REAL HotWaterlikefluid dashboard heat when the blend doors don't conspire to the contrary.915 trans that would like it's own heat zone please 75w swepco is thick @5°f.

Boxcar wrote: So, dropping pedal under braking is not a symptom of booster demise?

You ask the above immediately after reading:
"A booster leak/insufficiency exhibits a *rising* pedal, a sinking pedal suggests that your master cylinder is failing or you have a leak elsewhere in the system."

I, I, I don't know how to re-explicate it any more succinctly . . .

Boxcar wrote: Hieroglyphically yours,happily driving over and under salt encrusted 944. with REAL HotWaterlikefluid dashboard heat when the blend doors don't conspire to the contrary.915 trans that would like it's own heat zone please 75w swepco is thick @5°f.

Well, I have even real-er carbon monoxide-laced oil vapored engine compartment exhaust pipe-warmed air frothed by a 6,000 rpm cooling fan driven by a Pratt & Whitney turbine facsimile Bosch 38A generator that was built when the US had 210,000,000 citizens.
Dizzily Oxygen-Starvedly Yours,
ColinOfLateNightSojourn

Thanks Boss.I is informed.
M-Cyl scrutiny to follow.

...
Well, I have even real-er carbon monoxide-laced oil vapored engine compartment exhaust pipe-warmed air frothed by a 6,000 rpm cooling fan driven by a Pratt & Whitney turbine facsimile Bosch 38A generator that was built when the US had 210,000,000 citizens.
Dizzily Oxygen-Starvedly Yours,
ColinOfLateNightSojourn

Pictures please? Of some dervish watt making air moving part possibly coming to a town near someone.

Boxcar wrote: Pictures please? Of some dervish watt making air moving part possibly coming to a town near someone.

It is just the ol usual Type 1 engine that happens to hang the cooling fan on the end of the generator inside that big black lump of a fan housing with two dainty little ducts driving into paper hoses that feed the exchangers.
Colin

Thats what I was seeing.though the wordhaikutonepoemsalad dressing got me a bit a drift of typ1 squirrelcage spun by typ1 alt setup.
210,000,000 US population was a dead giveaway tho Boss.

I am concluding 'faulty brake vac booster' after idling engine and pumping brakes and hearing no change in rpm.
I also followed Chilton surprisingly good section on testing booster and neither procedure gave evidence of working booster.

Soo..can you give brief description of Rhode Island/rebuild ?

Also, i jave afew good late Bay boosters...wondering if they can be modified to be used on 71.

dingo wrote:I am concluding 'faulty brake vac booster' after idling engine and pumping brakes and hearing no change in rpm.
I also followed Chilton surprisingly good section on testing booster and neither procedure gave evidence of working booster.

Soo..can you give brief description of Rhode Island/rebuild ?

Also, i jave afew good late Bay boosters...wondering if they can be modified to be used on 71.

Mounting holes have to be drilled for late booster, other than that, I think it will work.
Rhode Island Rebuild was so hack, I couldn't possibly formalize it.
Colin

well what exactly fails in the booster ? some kind of diaphragm ? I assume just split the case with a prybar and dremel and go from there ? what do i need ? razor blades, jb weld ?

dingo wrote:well what exactly fails in the booster ? some kind of diaphragm ? I assume just split the case with a prybar and dremel and go from there ? what do i need ? razor blades, jb weld ?

Sometimes it is the diaphragm. Sometimes it is the control valve which has to proportion the vacuum vs atmospheric pressure as you apply the brakes. The control valve has to react to which direction the pushrod is going, more atmosphere as you release, more vacuum as you apply. As the inner part of the diaphragm executes your command, it changes the proportioning. It is sophisticated and it does suffer from moisture, rust and brake fluid.

The two cans are sweged together around the periphery under a good spring pressure with the diaphragm serving as the edge seal. It needs to be good. A bench vise would have helped us there on the stoop.
Colin

Brake booster switcheroo: late bay unit does fit on early Bay..just barely with not one mm to spare. Disengage the driver side e-brake cable and it slides right on. Using late Bay master cylinder and early resevoir. Everything else seems to be the same. Beer time arrived before i could test it out, but so far so good.
As for the faulty early unit..about a quart of dark brown stale brake fluid gushed out when i pulled the master cyl...the innards were predictably rusted like an old shipwreck

dingo wrote:Brake booster switcheroo: late bay unit does fit on early Bay..just barely with not one mm to spare. Disengage the driver side e-brake cable and it slides right on. Using late Bay master cylinder and early resevoir. Everything else seems to be the same. Beer time arrived before i could test it out, but so far so good.
As for the faulty early unit..about a quart of dark brown stale brake fluid gushed out when i pulled the master cyl...the innards were predictably rusted like an old shipwreck

Have you tested it, yet?
Colin

Yeah, seems to work OK. Took me a while to figure out why i was getting no boosting vacuum...that the steel tube was clogged and not allowing vacuum to pass. Assume years of corrosive brake fluid vapor had rusted it ? Bypassed with later style plastic..

Installed the plastic tubing lengthwise with little fuss, but now upon starting engine, i have vacuum leak...traced to the front side of the freshly installed booster unit....hissing from somewhere under the boot ! Can this be from the fact i had to depress the connecting rod to get the pin to fit in the linkage ? OK well then what am i lookin at ? o-ring in there ? damn, it looked like avery clean servo, as did the master

meanwhile, whilst pondering, i ripped open the old unit which was rusty, but the rubber diaphragm looked surprisingly intact

cant remember how to post images

so it looks like three possibilities..
-leaking rubber diaphragm,
-air valve : closed at rest, open when pedal depressed
-vacuum valve : open at rest, closed when pedal depressed

i guess i should test to see if hissing (at rest) stops when pedal depressed....