Alfa Romeo Forums banner

1 - 5 of 5 Posts

·
Registered
Joined
·
380 Posts
Discussion Starter #1
the info on the tech digest sticky doesn't seem to quite hit this one.

Pedal sometimes goes hard when depressed and stopping power is degraded. sometimes when this happens, more force will help and other times not.

engine's idle is fine. I get the "fffsstttt" sound when I depress the brake pedal while engine is off, but the pedal does not drop if I hold it down while starting.

What to try next ??

Cheers

Jeff
 

·
Administrator
Joined
·
17,465 Posts
See if the check valve in the vacuum hose is sticking. Remove it, squirt some carb cleaner into it, shake it to work the carb cleaner around, repeat once or twice more.

You should be able to easily blow through in one direction (towards the intake when installed) and not at all in the other direction.

A simple test for booster operation is to pump the pedal 6-8 times with the engine off. This bleeds off any residual vacuum in the booster. Then, while pressing on the brake pedal, start the engine. As vacuum is applied to the booster you should feel the pedal move down a little bit.
 

·
Registered
Joined
·
131 Posts
Also, after you have pumped the pedal to destroy vacuum as mentioned above, hold firm pressure on the brake pedal. If the pedal slowly travels to the floor, you have a master cylinder leak.
To me though, it sounds like you have an intermittent leak to your booster, often the grommet that holds the vacuum hose into the booster gets loose on older cars and can cause random issues.
A good way to check a vacuum booster is with a vacuum pump, pull a vacuum on it and see if you can hear leaks etc.
 

·
Registered
Joined
·
380 Posts
Discussion Starter #4
Thanks guys - good info.

I have noticed, however, that my car ('69) does not have the check valve on the vacuum hose. At least I don't see it. In the big parts house's catalogs a replacement check valve is shown as screwing into a threaded fitting on the intake manifold. The vacuum hose to the booster goes from the check valve to the booster. My car doesn't have that valve at all. hose goes right into a simple fitting on the intake.

I seem to remember there's something specific about this on the '69 cars. The check valve arrangement is different somehow (?) or missing, if memory serves (memory may not serve at all, of course ;)
 

·
Registered
Joined
·
1,610 Posts
On a 69, the check valve in the intake is very simple. It just screws in. The first one I had didn't have valve left, it was just the fitting. I installed a later one and everything worked great.

Will
 
1 - 5 of 5 Posts
Top