Check Engine light - Slight water leak

[John Larson]

You wrote:  "Hello,

I have a 1993 Audi 90S which I purchased 2 years ago.  The car has been
running great ever since I bought it and I haven't had much trouble
aside from normal wear and tear items.  This morning my check engine
light came on while I was stopped at a stop light."

..............................SNIP .......................................

"I took the plastic cover off my engine area and noticed a bit of "gunk"
on some of the hoses and saw a spot of coolant further down.  One hose
has some tape around it(looks like electrical tape)and it's one of the
hoses with the "gunk".  I checked for signs of coolant in my oil and oil
in the coolant and saw no signs of cross contamination.

Does anyone have any ideas or advice?"

Many thanks,

Floyd

Hi, Floyd!  One thing you have to remember, and it's something I have to 
tell customers and potential customers nearly every day, the "MIL" (or 
"CEL") is NOT in any way related to common mechanical problems.  Your car 
could be completely out of oil or coolant (or both) and the engine seized, 
and the CEL most likely would remain unlit.  It is, especially on a pre-1997 
(pre-OBD 2) car, solely a monitor of a small number of very simple EMISSIONS 
RELATED components and functions.  On later OBD 2 cars, there are literally 
hundreds of (emissions related) functions and components addressed, but on 
your car there are a dozen or less. Newer cars even monitor transmission, 
ABS, entertainment systems, HVAC, locks, seat controls, windows, alarms, and 
many other systems.  That said, you could have a flaky coolant temp sensor 
or wiring, an EGR problem, a crankshaft or camshaft position sensor problem, 
a Bad O2 sensor, a bad mass airflow sensor, or a bad catalyst.  I don't 
think a 93 even monitors an engine miss, though I could be wrong and I'm 
writing this from home, away from the book.  I can't even have a life on 
Sundays!
Anyway, I would do what you did, look the engine over, make sure the fluids 
are up, and try to define the conditions under which the light comes on.  I 
would call my mechanic on Monday and discuss it with him or her, get it 
scanned, and go from there.  John