E21 cooling problems
Subject: 323i overheating
Sent: 1/4/04 19.39
From: Asier, asierotxar@yahoo.es
To: Jeroen, jeroen@bmwe21.net
Posted on the bmwe21.net forum by Jeroen: 1/4/04
21:38
Replying to:
Hello, I'm from Spain and I want to ask something that can't find the
solution. I've got a BMW 323i e21 of year 1981, and always we have a problem
with the temperature of the engine, for example if you are driving some time,
and you stop the car, and you have the car anytime at slow motion, the engine
temperature go up, and stops at the next baar (or a litle more) of the optimal
temperature. We have asked at BMW mechanicals and many mechanicals and all tell
us that in this model is normal. One of the mechanicals try to install another
type of ventilator, but was imposible, because the cylinder head is very near
of the cool system. If somebody know how to end with this problem, please
answer me. Asier
Hi Asier,
Well, there are known temperature weaknesses in the M20 engine your car has.
First there's the viscous fan coupling that can break down and thus not give
enough airflow through the radiator. This is something that causes problems
especially at low speeds, because of the lack of 'driving-air'. The older E21
six cylinder cars as well as the air conditioned models had an electrical fan
in front of the radiator. It shouldn't be too hard finding one and with a
little electrical knowledge you should be able to get it running, manually or
automatically. But that should be considered a means to get extra cooling
capacity, not the way to work around a problem. So, is the current fan clutch
still ok?
But there are more weakpoints:
The water pump can be worn (I always advise people to change it every two
timing belts -when in Rome...)
The cooling system could not be building up enough pressure due too a worn
expansion tank fill cap.
Thermostats, even factory new ones, are a PITA too.. they can get stuck in any
possible position, in your case that could be slightly opened thus not
providing enough coolant flow.
A clogged radiator can ofcourse contribute to a flow problem, as well as a
badly bleeded cooling system. Finally, the temperature sender can be bad. I've
seen that before as well.
These are the most common weakpoints, at this moment I'll stay off possible
more serious problems like a head gasket. But, as long as the gauge doesn't go
too far past the three quarter mark, I wouldn't think about something more
serious, and if the temp doesn't go too far your cilinder head isn't at risk.
Good luck, and keep us all posted!
Rgds,
Jeroen
>>>Some additional comments by Jeroen, Jan 5, 2004:
·
Temperature gauges
in BMW’s, at least in every E21, should always be in the middle when the engine
has reached normal operating temperature. Ofcourse, slight deviations are
possible, but a temp gauge that never passes the ¼ mark, or a gauge that’s
always on ¾ … it may be harmless but something’s not the way it should be.
·
The water pump
problems occur mostly on six cylinder models.
Bleeding the coolant system: there are many theories, here’s what I
usually do:
·
4 cil: check
coolant level in the radiator, run the engine warm, when warm put on a few
gloves and squeeze the two big rad hoses tight, repeat 2-3 times. Beware of the
fan!
·
6 cil: jack up the
front of the car before filling the system. Make sure the interior heating is
on fully opened. Bleed screw (on top of the thermostat housing) must be closed.
Run the engine warm and check the coolant level in the expansion tank. Add some
coolant if necessary. As soon as the coolant starts to flow, put the cap on the
expansion tank. When the engine is warm, bleed the system using the screw.
After that, drive for a couple of minutes and bleed again, just to be sure.