From: bjgaed@bb1t.monsanto.com
Subject: Re: [A] '71 Super has CO trouble
Organization: Monsanto Company, St. Louis, MO
Date: Tue, 5 Jan 1993 14:21:11 GMT

In article <1993Jan4.175343.438@hsh.com>, paul@hsh.com writes:
> In article <1993Jan4.182324.5034@zia.aoc.nrao.edu>, troberts@zia.aoc.nrao.edu (Timothy Roberts) writes:
>> Hey, Folks!
>> 	I have the joy of breathing Carbon Monoxide everytime I drive
>> my '71 Super Bug.  My heater boxes are brand new.  My engine is
>> freshly rebuilt and runs like a top.  I can't smell a thing.  

[Comment by Wise Guy deleted]
> 
>> Questions:
>> 1) The pre-heated air hose slips onto the oil-bath air cleaner
>> housing, goes through the tin rear engine cover and goes WHERE?  I
>> can't find a place to attach the other end.
> 
> There is _supposed_ to be a little dingus that fits down there in that mess
> of muffler pipes, into which the preheat hose is supposed to slip.  (If you
> haven't seen it, I can't describe it better.)  However, most of us lose that
> dingus (if we ever had it) the very first time we 1) change the muffler 2)
> rebuild the engine 3) hit a bump.  That's not the cause of your problem
> anyway. 

The "dingus" looks like a flat piece of metal with a rolled edge and a 
short tube going through it.  The rear end of the tube is cut square, 
the front at an angle.  It hangs down behind #3 cylinder underneath 
the rear tin.  It is *hell* to put on with the engine in.  If you have 
it, fix it when the engine is out to replace the seal (see below).

> 
>> 2) The old engine compartment seal is rotten and very hard.  I can't 
>> see a way to replace it.  I was told a new one costs a mere $8.95 and
>> I was told "you just remove the rear engine cover."  Huh?
> 
> That is part of the problem.  But there are two seals under discussion -- the
> one you quote above is for the rear engine cover.  However, the one you
> should be looking at is the rubber seal that fits around the engine
> compartment -- if it's torn or missing, fumes can often enter your car. 
> Replacing it is easy -- once you pull the engine! 

There is a partial vacuum in the engine compartment due to the fan 
pulling the cooling air.  Those slots above the engine compartment 
cover should be the source of this air, but they sometimes get blocked 
with leaves in the rain tray underneath.  Be sure they are clear.  
Then replace all the seals around the engine tin and the hoses so no 
air can come in from underneath, where there be exhaust fumes.  If the 
fan sucks in exhust fumes they will find their way in via the heaters 
unless the flaps are *really* closed.

> 
>> 3) Why does my bug blow fumes even when the heater boxes are closed?
> 
It's probably almost impossible to *completely* close the heater box 
flaps, so it's important to have exhaust-free air comeing from the 
fan.  Check to be sure the heater cables are adjusted properly and 
that the flap mechanism and springs operate freely on both sides.  
They can crud up pretty fast.

One other possibility is an opening somewhere in the passenger 
compartment that is somehow sucking exhaust back from the tailpipes.  
It would take a wind tunnel to properly track this down.  Analogous to 
driving a hatchback or station wagon with the rear open.

> 
> Paul Havemann, VP        HSH Associates          (201) 838-3330 | 1-800-UPDATES


--Electric Monk            (Bruce Gaede); 
                            e-mail: bjgaed@ccmail.monsanto.com

"...and then time started seriously to pass."
--Douglas Adams, _Dirk Gently's Holistic Detective Agency_