Date:         Tue, 17 Jan 1995 10:40:23 CST6CDT
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         "Dan Houg" <fairwind@northernnet.com>
Subject:      coolant sensors

Just a short diatribe from the "I should've known better department."

A few weeks ago I posted a note regarding the near death of my
Toyota ECU (this pertains to VW's too, especially with all the talk
of air in the cooling system) and how I rejuvenated it my
unplugging/plugging it back in.  Well... I didn't quite hit the nail
on the head.  Seems my trouble codes were still being set
(indicating a bad water temp sensor or the ECU) and the car
continued to be unreliable-- stalling, bogging, etc. Sensor would
check out okay spec-wise.

Well), to make a long story short, I decided that 
the time  had come to buy a new car and end my frustrations, after 
all the Toya had 237,000 mi on it.  I came THAT close <picture narrow 
gap between fingers> to spending 18 grand on a new car.  I was half 
stranded with the Toya and out of town, hood up, staring 
dumbfoundedly at the engine trying to figure out what the H#LL was 
wrong.  I looked at the overflow coolant jug-- half full, but pulled 
the cap off anyway-- it was empty!  There was a scum line on the jug 
making me think it was full.  I pulled the radiator cap off and the 
coolant level was above the core but down a couple inches.  I bought 
a jug of antifreeze at the station I was 'stuck' at and filled the 
radiator and the overflow jug.   Folks-- the car has run PERFECTLY 
since then (about 400 miles).  With the air in the cooling system, 
enough tomfoolery was going on with the coolant sensor to trick it 
into telling the ECU all sorts of nasty things.

As my wife said, "So we just about spent $18,000 because your 
radiator was low?"  

3 lessons:
1.  Keep It Simple, Stupid.   KISS
2.  Don't assume things, check them out
3.  Electronic engine management is wonderfull but EVERYTHING is 
related.