[W126 Coupe] Re: VACUUM LEAKS

[Dan Gardner]

Thanks for the information Chet,you are spot on of course,I will price a set 
of hoses on Monday although they may be cheap in the US,parts here can be 
triple the price,ah well I will just have to bite the bullet,thanks again it 
was very informative.


Kind Regards  Dan Gardner    1986 560 SEC euro 220kw(300HP)

> Message: 3
> From: "Chet Hwilka" <chwilka@comcast.net>
> To: <mbcoupes@mbcoupes.com>
> Subject: RE: [W126 Coupe] Re IDLE AIR VALVE PIPE WORK"IS YOURS LEAKING"?
> Date: Sat, 15 Jan 2005 10:05:48 -0500
> Reply-To: mbcoupes@mbcoupes.com
>
> Hi Dan,
>
> Just replace the hoses.
> If the hoses are too soft (or too hard) they're not going to make a good
> seal.  Rubber is going to break down in time, under the conditions close 
> to
> the engine.  An air hose subjected to engine heat left undisturbed for 
> years
> hardens and seals itself.  Once the hose is moved or disconnected, the 
> seal
> is broken and it's most likely going to leak.  If those are the original
> hoses they lasted 19yrs, it's time...
> That goes for the all the rubber involved in the air intake to the engine.
>
> As you know, the engine requires an air/fuel mixture to run.  Fuel is
> regulated, basically, by the pressure regulator and fuel distributor.  The
> air is primarily regulated by the throttle valve (directly linked to the
> accelerator pedal).  The idle is basically set by the throttle closed
> position.  That closed position allows only enough air to get into the
> engine to barely keep it running (500 rpm).  The Idle Valve is controlled
> electronically by the Idle Control Unit which in turn receives its 
> controls
> for various sources (eng temp, speed, A/C, even the gear shifter, etc).
> The way the idle speed is adjusted, is the Air Valve allows air to by-pass
> the Throttle Valve and goes directly into the engine.  When the O2 Sensor
> detects more O2 in the exhaust, it tells the fuel distributor (thru the 
> EHA)
> to supply more fuel.  More fuel increases engine speed.
>
> So with the throttle closes at idle, any extra air that is sucked into the
> engine that by-passes the throttle is going to increase engine speed.
> That's any leaks in the any of the hoses after the Idle Valve.  Those 
> hoses
> are, the little one from the IV to the metal housing that the Cold Start
> valve mounts to, from there to a "Y" hose that connects to the left air
> manifold hose.  The other leg of the "Y" goes to a cross-over hose, that 
> is
> routed under the air/fuel mixture unit to the right air manifold hose.
> Those air manifold hoses connect to each fuel injector holders that are
> secured to the head by clamping the injectors down.  The holder has a 
> rubber
> o-ring sealing it with the head and the injector has a rubber seal, 
> sealing
> it to the holder.
> Any of those connections are sources for extra air..
>
> Also after the throttle there's a lower air plenum that's connect to the
> intake manifold through 8 rubber "O"  ring seals. Again a source for extra
> air that didn't find it's way to the engine through the throttle.
>
> Long story short.. Rubber is not going to last forever and has to be
> replaced in time, it's cheap.  You can't fault MB for that.  The original
> unclamped design lasted this long without leaking problems. Now if you've
> recently replaces the hoses and they leak, then the hoses are at fault. 
> If
> so, were they MB or after market?
>
> Hope this helps and sorry for the looong reply..  Must be the coffee..:)
> Chet
> 




-- 
No virus found in this outgoing message.
Checked by AVG Anti-Virus.
Version: 7.0.300 / Virus Database: 265.6.11 - Release Date: 12/01/2005