radiator fan inop , blown coolant resevoir = frustrated audi owner

[Marc Swanson]

I'll start with the questions and get on with grumbling afterward :-)

car: 88 90q
symptom:  radiator fan will not come on

I was in kind of a rush this morning as I was already late for work, but
I did a little diagnosis ruling out the most likely suspects.

So far, I have tried jumping the fan switch wires to rule out the sender
which resulted in audible clicking of the fan relay but no movement in
the fan. Next I disconnected the harness from the fan and hooked up my
DMM to the connector, which showed no power through the wiring when
jumping the connector.  Next I checked the two fuses that relate to the
cooling fan:  both were fine.

So, to save me some debug time given what I've tested so far, what's the
next most likely mode of failure?  I'm thinking I've got some melted
wiring under the fuse box to deal with.  Anyone BTDT?

<long and rambling story>

Ok, now for the rest of the story. I replaced my coolant tank when I did
a T-belt job on the car about a year and a half ago.  Fast forward to
about a month ago and I noticed some dried coolant showing up on the top
of the resevoir.  I didn't think much of it until about a week ago when
the coolant level warning light went off.  I was only about a mile away
from the gas station where I needed to fill up anyway, so I pulled over
and checked it out while filling up.

In my experience, that sensor is really sensitive.. even if the coolant
is down just a little bit it will piss off the sender.  Sure enough in
my case I was only down a little bit on coolant, but this time I could
hear hissing and could see a tiny pin-hole leak at the top of the
resevoir.  I wasn't too worried about it knowing I could probably make
it to work and back without incident, and I did.

When I got home, I put a little plastic epoxy over the leak and let it
sit overnight, then topped up the coolant.  So yesterday I take the car
to work and get the warning light again half way into work.  So when I
get to work it is down just a little bit but the epoxy clearly didn't
hold:  I could see the coolant fizzing out from the edges of the patch.
Again, not very worried about it I headed home.

I knew things had to be getting worse cause' now I could see steam
coming up from the edges of the hood in stop and go traffic and the
coolant gauge was climbing higher than normal (but not high enough to
make me pull over and stop). So I more or less raced home figuring I was
at a better advantage to get there before all my coolant leaked.  Got
home: too late, resevoir was completely EMPTY!  Naturally with my luck I
have a spare cooling resevoir, but it is at my folks place in NH: doh!
Further investigation as stated above showed that the cracked resevoir
was probably just a symptom of the bigger problem:  higher system temps
due to an inoperative radiator fan......

I think I got lucky and managed to escape without a blown head gasket as
one would expect after subjecting a poor car to such treatment.  I
didn't notice any coolant out the exhaust or oil mixed in with coolant
as I ran the car up to temp this morning with another failed attempt at
epoxy (JB weld this time...), so I guess I'm happy in that regard.

So now between two cars and a motorcycle, I'm down to just the bike to
get me back and forth to work (my TQ is down for a turbo job...).


I swear, my cars are going to be the death of me....

</long and rambling story>

--
-Marc
87' 4ktq
88' 90q
www.mswanson.com/audi