[alfa] Diagnosing a bad brake booster

[Jon Pike <jhpike@xxxxxxx>]

Jay beat me to it, mentioning the location of the one way valve in the
#4 intake manifold.. but I was going to suggest an alternative quick testing
method: remove the vac line at the booster end, and while using your calibrated
thumb to plug it, have an assistant start and idle the car.  You then can check
for flow, by uncorking the hose and observing a healthy suction.. as well as 
#4 probably missing with all that extra air.  The other test would be: have
assistant turn off motor while your thumb is on hose.. if you get vaccum and it
holds for a while, you don't have major leaks in the hose and valve.

Haven't tried this, but should work as described. If you suspect the one way
not sealing well, you could remove the hose at it's end, and spray a little
carb cleaner or similar down it's port, while the engine is running, to 
"degunkify" it and hopefully get it sealing tight again.

Hope it helps..

Jon
77 Spider
Irvine, CA




> Kevin Trent <trentkc@domain.elided> described the symptoms
> of his Spider's brakes (hard pedal, etc).  Yea, the symptoms you
> describe definitely sound like a bad booster.  There is a valve at 
> the back of the intake manifold, but that's just a simple one-way 
> valve to maximize the vacuum (e.g., minimize the pressure) in the 
> booster.  I guess you could unscrew it from the manifold, and use 
> the simple "blow in it from both directions, and confirm that air 
> will only flow one way".  I would bet that the valve will check out 
> OK.  While you are putting off the inevitable, you could also
> check the flex hose between that valve and the booster - make
> sure it isn't cracked/leaking.
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