Re: vacuum control valve

[jonathang@domain.elided]

Darran Gauci wrote:
>Subject: 1750 GTV brake booster hose

>I've just replaced a worn hose which runs from the brake booster to the engine intake manifold on my 1750 GTV.
>What puzzles me is that in the workshop manual I have, it appears to say something along the lines that this particular hose "incorporates a vacuum control valve".  Now the original hose which I removed doesn't appear to be
>anything special - just an average rubber hose.
>
>I'm wondering if someone more experienced can tell me if this particular
>hose does indeed include some sort of valve ?
>Thanks,
>Darran

Hi Darran,
The "vacuum control valve" is not incorporated into the servo-to-manifold hose itself, it is actually the part that sticks out from the inlet manifold which you slide the hose onto. If you were to look closely you'll see it has flats for turning with a spanner... inside is a simple spring and ball-bearing valve. When the motor's running the low pressure zone in the inlet manifold opens the valve and allows scavenging of air from the servo hose and unit into  the manifold. At lower revs or when the engine is switched off the valve closes to allow the servo to retain its vacuum and maintain some braking assist function.

As an aside - a 1750 Berlina I had a few years ago had a ticklish brake problem. Every time I prodded the stop pedal it slowed well but when I released foot pressure they would stay on for anything from 1 to 4 or 5 seconds! Eventually I traced the cause to a vacuum servo hose that had delaminated internally and was "pinching together" inside every time I applied the brakes - disconcerting when you get hooted from behind at lights for not moving off fast enogh! So I reckon you're doing the right thing there Darran.

Jonathan Griffin

Giulia Super 2000 race car (resting before the new season)




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