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Re: Engine after run system problem

Hmmm. This explanation sounds exactly like what is going on with my 5kcst.
Except for one problem: The fan and pump (both new!) do come on as specified.
They only stay on for a few seconds. Is this an alternate failure mode for this
thermoswitch (close, then quickly reopen) or should I suspect the relay? It does
come on when I short the wires.
Thanks for bringing this subject up again. Unfinished discussion on my part.

James A. Desveaux wrote:

> Mike:
> It's fairly easy to check out whether there's a problem with the
> turbocharger coolant pump afterrun on your S4.  If you drive the car and get
> it up to operating temeperature (and use the turbo a bit to accelerate the
> process), and then let it idle until the rad fan comes on.  Shut the engine
> off immediately and wait in the car for about 5 minutes.  THe low speed fan
> should come on, and with it the turbo coolant pump.  If the fan comes on,
> you can take a rag in your hand, and put it around the coolant pump to
> determine if it's vibrating (pumping).  Make sure the car is good and
> warm/hot when you do the test, because the thermoswitch for the coolant pump
> is fairly sensitive.
> If nothing happens, remove the two wires at the bottom of the thermoswitch
> which screws into the bottom of the inlet water manifold under the intake
> manifold.  Jump those two wires (you can also perform this test when the car
> is cool).  If the fan and pump come on when you touch the wires, you've got
> a bad thermoswitch (part #054-919-369B), about $30 from the dealer, or $11.
> from the Parts Connection.  If the fan still doesn't come on when you touch
> those two wires together, check the fuse.  On the '91 200Qs with the 3B
> motor, it's fuse #21, and it should be a 25 amp fuse.  It might be the same
> fuse on the S4, but I'm not sure.  When I first bought my car, I had this
> problem.  Turned out the previous owner or somebody else had stuck a 10amp
> fuse in there, and it was blown.  By the way, that thermoswitch is very easy
> to change.  Anyway, if it's none of these things, you might have a broken
> wire somewhere.
> - Jim