I'm steaming

[Brett Dikeman]

I can't guarantee it, but $20 says your radiator fan failed to 
operate properly; the dead giveaway was that the failure happened 
once you stopped/slowed down.  At highway speeds(even 40mph or so), 
there's more than enough airflow to cool the engine, but at slower 
speeds or stop+go, the car needs some a help from the fan.

The source of the coolant was almost certainly the pressure release 
valve in the cap, if the fan didn't work properly.  Make sure it's 
replaced after this whole thing is over(especially if it's rather 
old; I think Phil was the one who recommended these guys get changed 
every so often.)

The failure, if it was cooling-fan related, could either be the fan 
itself, related wiring(like the fuseable link or the resistor pack), 
or the circuit specific to the second-stage fan(such as the 
multifunction sensor, or the wiring connected to it.)

You can quickly check the fan system overall by switching on the 
ignition, and seeing if the fan comes on low speed when you put the 
climate control into auto mode(note, it must be above 40 degrees F 
outside for this check to be valid; A/C won't come on below about 40 
degrees.)

The fact that you got a high-temp warning means that the 
multifunction temp sensor was working fine(it activates the 
second-stage fan, puts the ECU into limp-home mode, and disables the 
a/c clutch circuit, all by raising the voltage on one line, which the 
auto-check system monitors.)  So it's not a very likely suspect.

I'd examine the fuseable link; also, watch the link while the 
ignition is on and the cc in auto mode; look closely for 
sizzling/sparking that could occur with a corroded connection.  Make 
sure voltage is getting to the fan, and that there's a good ground. 
I believe the ground side is switched, NOT the positive, so be 
careful and work with the Bently, disconnect the battery when 
appropriate, etc.(you can easily spot-weld a socket wrench handle to 
the body no problem etc.)

The Bently probably has specs on proper resistance values for the 
motor, along with a complete diagnosis flow chart that's better than 
what I put above...

BTW, has anyone every wondered how much mileage could be improved by 
a simple circuit that detected when the vehicle's speed was over a 
certain range, and shut off the first-stage-a/c circuit?  Although, 
with all that air forced through, the load on the fan must be very 
low(and hence current usage?)


Brett


At 11:43 PM -0400 4/7/01, Kent McLean wrote:
>Well, my '89 200 TQ is.  I came off the highway after a
>1-1/2 hour run, and got caught in traffic on the off ramp
>onto S. Willow St. in Manchester (NH to those in the UK).
>Took 10 minutes to work my way up the ramp when the water
>temp. warning light came on and the chime went off,
>followed by huge clouds of steam billowing out from the
>edges of the hood. D*mn.
>
>Looking under the hood, lots of green water everywhere,
>the sweet smell of antifreeze. I couldn't tell the source.
>It may be a hose, it may be the radiator (although the
>bottom of the radiator seemed dry).
>
>I let AAA take it to my local service station. They don't
>open until Monday. Until then, I'll dream of getting rid
>of it for an S6.  And I'll stop thinking of upgrading to
>a cheap V8, which doesn't get me past the problem of
>maintaining an old car.
>
>Cheers,
>Kent McLean
>(who is very happy that BC beat UND tonight in overtime
>for the NCAA Men's Div. 1 Ice Hockey championship.)