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From: rob@lzmi.UUCP
Newsgroups: net.auto
Subject: Re: Honda Prelude noise
Message-ID: <153@lzmi.UUCP>
Date: Wed, 9-Nov-83 11:51:54 EST
Article-I.D.: lzmi.153
Posted: Wed Nov  9 11:51:54 1983
Date-Received: Fri, 11-Nov-83 02:00:41 EST
References: <648@ihuxi.UUCP>
Organization: AT&T Information Systems, Lincroft, NJ
Lines: 20

I also have a Prelude, and have experienced a noise (more of a whistle
than a hum) in the summer during extemely hot days, as you described.
It was explained to me that it was the pressure release valve in the
gas line between the gas tank and the carb. As the tank gets heated
by the ambient tempature, the vapor pressure inside the tank goes
up, and the valve tries to equalize the pressure. This whole scheme
is implemented to get around the problem of the gas cap blowing off
in your hand when you stop to fill the tank (so they say...) on 
a hot day. It also helps the carb perform better if the vapor pressures
are equalized.

I pressed the dealer to change the valve, which he did under protest,
claiming that it wouldn't help, and he was partially correct.
The noise did NOT stop, although the volume did drop somewhat.

My wife drives a Civic Wagon, and we have heard the same thing
with her car, but not as loud.

It must be a badly designed (i.e. - NOISY) valve. If anyone has
a solution, please (PLEASE) post it to the net......rob