rad. fan question

DAK dak at rochester.rr.com
Sun Feb 23 15:31:43 EST 2003

Last night, my car dumped coolant! It had been running for 10-15 minutes
in a parking lot (wife was there with sleeping child). I was inside
paying for some groceries. Anyway, she comes in (with child, now awake)
and explains something wrong with the car, smoke coming from under the
hood, heard a knocking sound. (yes, she did shut it off right away).
Great! :-/
So, I go out to find some steam coming from under the hood. Pop the hood
to find a little more steam rising, and coolant over the engine bay
behind the radiator. I see it up on top of the ABS pump housing also...
I thinks to myself... must have been quite a spray to get up there! I
don't see any visible holes in the cooling system (no radiator neck
failure, no hose gashes). I loosen the coolant cap and more steam rushes
out! Hmm, must be holding some pressure. So, I let things cool for 10-15
minutes, then put in more coolant/water. We drive home without incident.
I pop the hood in the garage, but nothing unusual to report. So, I'm
thinking something to do with high under hood temps kicked in and caused
a problem... aux coolant pump? looks fine... Hmm, perhaps the radiator
fan didn't kick in and the coolant cap vented the pressure! That is my
working theory.
Looked at SJM's site, Bentley... go out the garage and attempt to
energize the fan motor. fan spins when I turn it... disconnect wires,
use jumper cables... it cranks right up! I let it stop and do it a
couple of more times to be sure it is working normally. So, I reconnect
the ground and try again... the fusible link smokes! I try again, more
smoke.. OK, something strange. I put a meter lead on the link, but it
falls apart with very little pressure.
My question is, does a failing fan motor require more current than
usual? I've heard about this on electric fuel pumps. Might the fan not
have kicked in on the stage 1-2 settings, allowing the car to overheat?
It powered right up with direct 12VDC applied. I need to get a new
fusible link (and spares), then I'll diagnose the low speed controls
(thermo switch, resistor pack...) If the fan is going bad, could there
be a certain position that won't work (bad commutator)?

Any other theories?

BTW. a couple of months ago, I had a mysterious coolant loss in the
garage. Couldn't see any thing leaking, just found some coolant (perhaps
a cup or more) on the garage floor. (put extra in the trunk at that point).



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