Re: Water circulation pump?

[Wallace White <wallace@remdesign.com>]

Jack -

In addition to what Avi said... Whenever the radiator fan comes on after
you've turned the car off, the aux water pump turns on at the same time.
The after-run relay runs the fan and pump until the coolant temperature
(measured by a two-wire thermoswitch on the coolant output flange) drops
to an acceptable level or until a timeout (10 minutes?). 
The fan by itself doesn't do a whole lot to decrease the coolant
temperature at the engine block, so cars with dead pumps tend to have
their radiator fans running for a long time after shutdown (often the
full 10 minutes or whatever) instead of a couple of minutes. Some people
have found this electrical drain to make starting afterwards difficult;
I suppose this is especially true for cars with a weak alternator or
battery.

BTW, a seized pump often causes the after-run relay to fry one of its
transistors, so that a new pump won't run. If so, not to fear: there's a
$1 Radio Shack part (NPN TIP 31, I think) to fix that. 

The pump costs about $120 at the cheapest (The Parts Connection has them
on sale sometimes) and the pumps are not known for long-life. Avi's
altnerative certainly sounds promising.

- Wallace
  '87 5kcstq 152k

Jack Gagnon wrote:
> 
> I noticed an electric water pump in my 87 5kcstq and a previous owner
> bypassed the pump for some reason.  My mechanic said it is to cool the turbo
> after the engine is turned off.  Why would it be necessary to bypass it? and
> if I let the turbo spool down for a minute or two before shut-down is it
> necessary?  I will probably fix it soon, but I need to earn some more money
> first.
> 
> Thanks
> 
> Jack