[alfa] 156 overheating

[Jonathan Coates <jon@xxxxxxxxxxxxx>]

Some thoughts which may or may not help. If the logic is wrong anywhere, 
somebody please point it out.
The cooling system works by running water araound a circuit using a pump.
The water gets heated in the engine and cooled in the radiator either/or 
the heater matrix.
The car shows overheating symptoms when moving slowly / stuck in traffic - 
seems like a low airflow over the radiator takes away less heat - fan 
problem?
Switching on the heater introduces a second method of cooling the water - 
Temp. goes down - hot comes out of heater - ergo water is going round and 
round.
Water is also going through radiator as fast moving car does not get hot.
Seems like the radiator fan is not doing what it should i.e. switch on and 
provide sufficient cooling airflow over the radiator to take away the heat.

Investigating further - parts CD ( I have no 156 manual) appears to show 
water pump driven off the smooth side of the cam belt.
I can find no mention of the fan temperature switch on the parts CD so I 
don't know where it is.
Parts manual does, however, show a resistor on the radiator fan page, 
though no wiring diagram to show what it is for.
Parts manual also doesnt show (or I can't find) the sender unit. On my 164 
the sender has two terminals so that one does the gauge, the other does the 
light. dont know which way the 156  does it.

My guess so far is that the problem lies with the fan and is electrical in 
nature. Either the switch is kaput (see below) or the resistor is too 
resisty and is not running the fan on full speed (guessing that the fan is 
a  two speed affair similar to a heater fan). Could also be that the high 
fan speed is not functional.

Possible tests / solutions:-
IF the fan switch is suspect (and it is) then you can bridge it to make the 
fan run all day, controlling the engine temperature with the thermostat, 
kind of like driving in very cold weather thsi should do no harm. All my 
cars have a piggy back terminal on one side so that bridging this switch in 
extremis is easy.
Bridging the fan resistor could make the low speed turn into high speed, 
though this is not a very good idea as the low speed wiring might not be up 
to the higher current draw, which will take away the heat more effectively 
showing that the high speed is disabled.


Other possibilities:-
The radiator on the 156 has the supply and return on the same side of the 
radiator. Presumably the radiator header is split internally so that the 
water flows across the radiator and back again. If the baffle is not there 
then the water can short cut the radiator. Does the other end tank get hot 
I wonder?

HTH
Jonathan Coates
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