[alfa] Brake Booster diagnosis, repair, & replacement?

[Kevin Trent <trentkc@xxxxxxxxxxxxxx>]

I have previously reported brake booster problems on the '79 spider I'm 
trying to bring back to daily driver status.  The symptoms are a very hard 
brake pedal and high pedal pressure to activate the brakes. If you start 
the car with a foot on the brake, there is no "drop" of the pedal when the 
engine starts and vacuum is created.  I am almost certain that the booster 
is not working properly.  I've checked the vacuum hose and the vacuum 
fitting on the #4 intake throttle, and both appear to be in good 
condition.  I initially thought that driving he car (which had sat for 3 
years) would loosen thing up, but after at least 200 miles there is no 
change.  All 4 brakes work equally well and release.  I've had brake 
boosters go bad before, but those had symptoms of a leaking booster 
diaphragm you could hear and pulsating pedals.   If I pull vacuum on the 
hose, the booster seems to hold the vacuum.

A Google search yielded some references to the booster and its "check 
valve".  What and where is the check valve on these ATE boosters?  Could it 
be rusted or stuck shut?  Is it that valve on the # 4 intake?

Is there any repair that can be done with the booster installed in the car?

Are there any diagnostics I can perform to pinpoint the problem?

I have a booster/pedal unit from a parts car that I think is good, but 
swapping the unit out is a PITA.  Before I go that route is there anything 
I can do to make sure the current unit is bad (or the replacement unit good)?

THanks in advance.  //kct Powell, TN
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