re: E36 overheating

["Sean Murphy" <scm1@xxxxxxxxx>]

Hi David,

I have just read about your troubles and thought I
would attempt to offer some guidance / help.

>>I have a very big headache.  My 92 325i keeps
overheating.  Initially my
>radiator tank cracked so I replaced that,  thinking
everything is fine,

Do you mean you replaced just the plastic reservoir on
the side of the radiator? I didn't know it was possible
to do that!

>I drive about a block and my car overheats.  I then
replaced my
>thermostat( 76 degrees Stant),  drove about  a block,
again overheats.
>I then think to myself change the water pump so I did,
drove a block,
>overheats.  What's interesting is at idle it's fine,
its only when I
>drive.  Also the plastic tank where I pour the coolant
in is not
>circulating(is it supposed to when car is warmed?).
Is it the
>aftermarket radiator(it fits fine)?  The radiator cap?
Sensor?  All
>your inputs will be greatly appreciated.

This sounds to me like the classic air-lock scenario.
Did you have the heater switched to maximum heat
position before draining coolant? Did you remove the
engine block drain plug? Are you sure that you bled the
system properly on refilling by using the small screw
next to the header tank filler cap? (I also bleed mine
after filling by running the engine on idle or just
above and opening the bleed screw until coolant only
escapes, i.e.. no bubbles)
I would recommend that you drain the coolant again
(remember the heater position), and refill SLOWLY with
the bleed valve open.
The only good point to all these troubles is that you
now have a nice spangley new water pump and thermostat.
(You have put the water pump drive belt back on haven't
you....?)
As I said, sounds very like an air-lock in the system.
Nothing that a bit of light work and patience shouldn't
fix.

Good luck and hope this is of some use.

Regards

Sean
http://homepages.tcp.co.uk/~scm1/bmw.htm

'93 E36 325i SE (24v Vanos)

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