Running Hot - Causes

Tue Jul 10, 2007 2:41 pm

Ive owned my 320 for a few months now and all has been great.
When i first got the car the coolant temp always sat just below the half mark.
Recently i've notices that the fan has been running a lot and the temp has been gradually climbing.
It now sits at the 3/4 mark which is worrying me, occasionally going just over the 3/4 mark.

Is this likely to be a failed water pump? Is the water pump a common weakness?

I don't think its the head gasket, its not showing the sual signs if it is.

If it is the waterpump can someone advise to the likely labour costs of replacing the pump and cambelt and time it takes.

Cheers in advance

Ashley

Tue Jul 10, 2007 2:59 pm

i had a similar problem and was told that the viscous fan was the cause. it is a common fault on e30s,luckily it is pretty cheap to change at aprox Ã‚£50 including labour .

Tue Jul 10, 2007 3:01 pm

Sorry to sound like a pleb but do you know what the viscous fan is??

Tue Jul 10, 2007 3:34 pm

Basically the fan which is powered by the fan belt is attached with a heat sensitive connection. When the engine is hot it binds giving more kenetic energy to the fan spinning it faster and cooling the radiator.
When it is cold, it releases the pressure and so the fan 'slips' which doesn't cool the radiator down so well.

The big metal centre to the fan on the engine front is the 'viscous coupling'

Tue Jul 10, 2007 3:40 pm

To test the coupling, run the car to normal temperature and turn the ignition off.
Wait for the engine to stop turning and then spin the fan by hand.
If it spins easily and continues to spin it afterwards then it needs replacing.

Tue Jul 10, 2007 9:01 pm

After having a good look i found the top rad hose to be very hot but the bottom one cold.
Sounds to me like water pump failure
Agree??? or could it still be something else?

Cheers

Ash

Tue Jul 10, 2007 9:33 pm

that just means the thermostat isnt opening. Take it out, put it in boiling water and see if it opens.

Tue Jul 10, 2007 9:48 pm

M20 water pumps can and do fail, but normally the result is a water leak, not a circulation failure.
If the car overheats only when moving slowly or stopped, then comes back to normal temperature when moving fast, then the viscous coupling is the likely culprit.
If it overheats at all speeds, then the thermostat is the first thing to check, as Munky says, or it could be a partly blocked radiator.
Of course, the gauge could be telling fibs! Tighten the small brass nut on the back of the instrument cluster, immediately behind the temp. gauge before getting too involved.

Tue Jul 10, 2007 10:48 pm

whats your heater like is it very warm not got a bit of an airlock hav ya just a thought