Flashing Coolant Light

[amalventano1@comcast.net (Allyn)]

whew, this is gonna be painful to explain...
i fully agree that the bubble contracts as pressure rises. keep in mind that it doesnt go away fully
(the primary coolant loop of a nuclear reactor is very similar to a cars coolant system). reactors
run at about 2000 psi, and they do have a 'reservoir' so to speak, and it keeps a decent bubble even
at that pressure. now here is how we get the bubble. since our coolant systems run at saturation
(unlike a reactor, where only the reservoir runs at saturation), the majority of the boiling will
occur at the hottest point in the system (and NOT in the core, as that would be a bad thing: i.e.
chernobyl pops, anyone?). cavitation of water through the head (or the core, in the reactors case)
causes non-condensable gasses to collect (argon, etc). this eventually results in a bubble of gasses
trapped in the head. with the car off and cool, you have 2 bubbles, one in the reservoir and one in
the head. half way into warm-up the reservoir dips slightly below the trip point, resulting in the
light. once fully warmed up, cycling the ignition while coasting will clear the light (sound
familiar to those of you plagued by 'the bubble'?).

likely causes of 'the bubble':
* if you have the problem right after filling:
1. you didnt get all the air out when you filled :)
2. corrosion/blockage in head/block/radiator trapping air
* if you get it a few weeks after filling:
1. corrosion by-products in the coolant system (rust, oxidation of head)
2. combustion gasses leaking by the head gasket (this happens in every engine, seal is not perfect)
3. pure water put in system (no lubricants + high temps makes oxidation happen faster) even a cup of
antifreeze is enough to prevent this problem.

the rieger had this problem and it went away completely when i ran some purple power through the
coolant system at temperature. i think i lost 2 pounds of brownish/blackish goo out of my coolant
system when i did that.

anyhow, im on leave, enough nuclear babble for this week :)

Allyn Malventano, ETC(SS), USN
87 Rieger GTO Scirocco 16v (daily driver, 180k, rocco #6)
86 Kamei Twin 16V Turbo Scirocco GTX ('it has begun', rocco #7)
86.5 Occo 16v Trailer (dotting 'i's across the country, rocco #8)
87 Jetta 8v Wolfsburg 2dr (daily driver, 260k, 0 rattles, original clutch, driveshafts, wheels :)


----- Original Message -----
From: "Larry" <rocco16v@netzero.com>
To: "Allyn" <amalventano1@comcast.net>; "John Erickson" <ranahan@charter.net>;
<scirocco-l@scirocco.org>
Sent: Saturday, August 17, 2002 10:56 AM
Subject: Re: Flashing Coolant Light


> Al-
>   As the engine heats up, the coolant expands as much as the air.  In fact,
> the bubble will decrease in size since air is compressable and water is not.
>  I had this same problem (as John is experiencing) and was able to fix it
> quite easily (as a result of a suggestion that the Meze gave me).
> (Ah, the Meze.  He may not have the fastest, quickest, best-looking Scirocco
> in San Diego, but he sure has a brain in his head...)
> :)
>
> Larry
>
> > better check for air in the rest of your coolant system. this will allow
> the bubble to expand as
> > your engine warms up, tripping the sensor.
> > Al
> >
> > ----- Original Message -----
> > From: "John Erickson" <ranahan@charter.net>
> > To: <scirocco-l@scirocco.org>
> > Sent: Friday, August 16, 2002 2:01 PM
> > Subject: Flashing Coolant Light
> >
> >
> > > My coolant light (the one in the gauge) has started
> > > flashing at me on a pretty regular basis, but not all the
> > > time.  The Bentley appears to be fairly worthless in this
> > > area.  I have been unable to find the circuit (in the
> > > manual) that runs to the sensor in the top of the
> > > expansion tank.  I have replaced that sensor to no avail.
> > >  My next thought is to clean up the connectors on the
> > > instrument cluster, but since everything else works well,
> > > I have little hope here.
> > >
> > > Has anyone had any experience in this area?  I'm tempted
> > > to just disconnect the bulb, but would like to make an
> > > effort to fix it.
> > >
> > > TIA
> > > John.
> > > Long Beach.
> > >
> > > _______________________________________________
> > > Scirocco-l mailing list
> > > Scirocco-l@scirocco.org
> > > http://neubayern.net/mailman/listinfo/scirocco-l
> >
> >
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> >
>
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