Strange Cooling Problem (Alfa 75 TSpark)
Discussion
After a track session at an airfield day on Monday, I was shocked to
find that my 75 had dumped a load of coolant on the floor under the car.
A quick check showed that the radiator fan switch had failed, so I
topped up the coolant, bridged the switch connectors so it ran
continuously on the ignition and largely ignored it for the rest of the
day (although I did get into the habit of cutting the engine and letting
the fan run for a while before killing the ignition from then onwards)
However, later in the day, I pulled into the Severn View services to
grab a coffee and came back out to find it had done it again. When I
parked up this time, I didn't give the car a couple of minutes to cool
with the fan on.
The temp. gauge is reading normally - never climbed above 85-ish
degrees. I know the guage is working, 'cos I've seen it climb as far as
110 degrees in traffic.
The water is coming out under pressure from one of the hose connectors
on the expansion tank.
Any ideas? - I suspect the expansion tank cap may be allowing pressure
to build in the system rather than letting it bleed away. Is this a
possibility?
I'm ordering a new expansion cap, fan switch, thermostat and hoses next week.... hopefull that'll fix things.
find that my 75 had dumped a load of coolant on the floor under the car.
A quick check showed that the radiator fan switch had failed, so I
topped up the coolant, bridged the switch connectors so it ran
continuously on the ignition and largely ignored it for the rest of the
day (although I did get into the habit of cutting the engine and letting
the fan run for a while before killing the ignition from then onwards)
However, later in the day, I pulled into the Severn View services to
grab a coffee and came back out to find it had done it again. When I
parked up this time, I didn't give the car a couple of minutes to cool
with the fan on.
The temp. gauge is reading normally - never climbed above 85-ish
degrees. I know the guage is working, 'cos I've seen it climb as far as
110 degrees in traffic.
The water is coming out under pressure from one of the hose connectors
on the expansion tank.
Any ideas? - I suspect the expansion tank cap may be allowing pressure
to build in the system rather than letting it bleed away. Is this a
possibility?
I'm ordering a new expansion cap, fan switch, thermostat and hoses next week.... hopefull that'll fix things.
I'd nominate air in the system, combined with sorting that fan switch - underbonnet engine temperatures are hottest immediately after the car is shut down so this is when the fan is most needed. The temp gauge could also be off it there is air in the system - I had an old pug once that registered fine on the guage, but mostly because the sensor was in air that doesnt conduct heat nearly as well as water 
Thanks.
Sounds possible - I chucked the car at my local mechanic to do a few jobs on it before the track day. Was going to do the coolant myself, but let him do it whilst he had the car.
I bet he didn't know about the special bleeding procedures.
I'll get everything replaced then refil and bleed the system.
Next job..... uprated discs and pads on the front.
Sounds possible - I chucked the car at my local mechanic to do a few jobs on it before the track day. Was going to do the coolant myself, but let him do it whilst he had the car.
I bet he didn't know about the special bleeding procedures.
I'll get everything replaced then refil and bleed the system.
Next job..... uprated discs and pads on the front.
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