E30 318 Engine coolant problem

[lee_edwards]

im not sure whats up with my bmw, driving it day to day i doint have a problem, the temp gauge sits nicely @ the 1/4 mark

but when i stop and sit in traffic ect... the temp rises up quite slowly and when its reaches the 1/2 mark on temp gauge it starts chucking water out of the radiator / cap area. then all of a sudden i have huge amounts of air in the system...??

it has done this a few times on me now, iv bought a new radiator cap thinking mine might be dodgy and not holding the pressure.... but again it has dont it today.. maybe might radiator has had it?

Thanks
lee

[Brianmoooore]

Sounds very much like a description of the effects of a duff viscous fan coupling.

[lee_edwards]

what are the fixes for this? new one?

how tight should the fan go when the engines warm? or how can i test if its working

[Brianmoooore]

When the engine begins to overheat, the fan coupling should lock just about solid. Revving the engine should produce a sound like a light aircraft on its take off run.
I have heard of a procedure where they can be refilled with fluid, but the usual cure is to replace.
It's also possible for a duff radiator to cause this problem if it has a serious blockage in the middle, so that not enough hot air is produced to lock the fan, but this is unusual.

[lee_edwards]

okay well i will start looking for a new fan then.. any ideas where to get one from?

someone suggested welding the viscous fan solid??? surely it would cause the engine to run way to cold wouldnt it?

[Brianmoooore]

someone suggested welding the viscous fan solid??? surely it would cause the engine to run way to cold wouldnt it?

Wouldn't affect the engine temperature in the slightest - that's set by the coolant thermostat, but it would certainly affect the fuel consumption.
You can fit a good second hand coupling, or they're available from the likes of GSF and ECP.

[lee_edwards]

i have fitted a new coupling from gsf... i take it my old one was buggered because you can hear the fan all the time now!

Although it hasnt sorted my problem, having abit of a spirited drive the other day my temp got up to the 1/2 mark. i then took it easy on my way home to cool it down abit but it hardly moved. the next day i when out init and the temp shot up to 3/4 very quick, then came back sensible and then went to the 1/2 and stayed there. when i started it up after about an hour, it soon warmed up and went to the 1/2 i had the heaters on full and it was blowing cold air. soon after driving off the heaters were blowing warm air but the temp stayed at 1/2 again

Any ideas anyone?

thanks

[Brianmoooore]

You have air (or other gasses) in your cooling system. If you haven't had the cooling system apart, then it's probably 'other gasses' which are likely to be combustion gasses leaking into the cooling system.
Bleed the cooling system properly, and hope. If the problem returns, you need to get the space above the coolant in the header tank tested for the presence of exhaust type gasses.

[lee_edwards]

when you say bleed it properly, how do you mean?

the only way i can bleed it is through the bung on to of the radiator next to the cap, because the bleed screw in the housing on the engine is seized solid!

i have done a pressure test for head gasket and the results seemed tidy.

[Brianmoooore]

Bleed it by pulling off the upper heater hose from the stub pipe on the bulkhead, and replace the hose with coolant flowing from both parts.