RE: <E30> Engine temperature problems, help!

["Fadeev, Alex" <Alex.Fadeev@xxxxxxxxxxxxxx>]

> I have a 1989 325i who's temperature is driving me nuts.  At 
> highway speeds, it's always at slightly above the 1/4 mark on
> the temperature gauge, regardless of whether the AC is on and
> what the outside temperature is.  

	That's not right. The temp gauge (if working) should hang around 1/2
mark (12 o'clock) all the time. Could be a bad thermostat that is stuck open
all the time ($20 at the dealer). Replacing is a very simple 15 minute job
(see Bentley or ask on the Digest).

> In stop and go traffic, the temperature will settle on the 1/2
> mark. However, if you turn on the AC and are stuck in traffic,
> it will move toward the 3/4 mark. If it's hot out, then watch
> out... I usually shut off the AC before it hits the 3/4 mark 
> (sometimes it stops at 3/4, sometimes it will start to move 
> beyond it)

	With AC on, your auxiliary fan should run in low speed to provide
additional air flow. Aux fan runs at high speed whenever the coolant
temperature is above a certain level (forgot the exact temperature - see
Bentley).
	It sounds like either your aux fan resistor is shot (rectangular
black box in front of the fan at 4'clock position) or the aux fan itself is
dead. 
	Bentley has instructions on what wires to short at the coolant temp
sensor to induce aux fan to spin at either speed. The fan is not cheap
(~$250) but necessary if run AC. The resistor failure is common with age. 

> The radiator is relatively new, the auxiliary fan resistor was changed
> recently, and according to my mechanic - who tried to stop the fan at
> idle, told me that the fan clutch was ok.  The thermostat was also
> changed very recently.  He said that this problem happened with older
> cars sometimes because  the engine and cooling parts don't mate as
> well and the heat transfer isn't as good.  Doesn't make a lot of sense
> to me.

Agreed.
I would double check the aux fan resistor (if the aux fan clutch is dying it
can fry the resistor). 
Also check the coolant temp sensor (on the passenger side of the radiator).
If its readings are off the aux fan will never get the signal to spin.
Replace the thermostat. 
 
good luck,
alex

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