411 (1969/1970) cooling fans

[john smith]

When my engine (383) is hot (fans running) and I switch OFF the engine, both fans stop.

This is the way it has worked for the past 35+ years.

The other day, the fans continued to work after switching OFF the engine (like I would expect in most modern day automobiles).

Which is correct – fans stopping immediately the engine is switched off (key removed from the ignition) or continuing to operate until the radiator is cool?

Have I had fault for all these years and not known it?

Many thanks -

[Peter.Kent]

Can't think why your electrics have changed the way they operate. But, it surely makes perfect sense to circulate under bonnet air and keep that big mass of iron a little cooler. The heat generated by those enormous exhaust headers when at rest is considerable. Stand by the car with the fans running and you will feel the hot air being blown through. ACCS fit an adjustable thermostatic switch and bypass the ignition switch so this all happens in a controllable way. Peter

[sjp63]

Mine stop when the engine is turned off. If ign switch is then moved to pos 1 they will continue to run until thermostat stops them

[GREG]

Surely a fan running after the engine has been turned off is only cooling the radiator and not the engine !

[Peter.Kent]

No: those two fans blast air through the whole of the underbonnet area. As I say, just stand outside the car when they are running. One car I had, you popped the bonnet to let the heat out. Fans on a proper switch much better. P

[GREG]

And I thought that Bristol's were water cooled !

[john smith]

Thanks Peter
Though the years past, I often wondered about this but always thought this
is the way Bristol Cars meant it to be.
I also wondered about the drain on the battery if the fans ran for even a
short time.
ACCS???
Sorry, not familiar with them.
Little more information please.

[john smith]

Sjp63
Thanks for your suggestion - maybe this is what I did unwittingly, moved to
pos 1 and hesitated.
Next time the engine is hot I will try what you have suggested.
I will follow up Peter Kent's thoughts about bypassing the ignition switch
to the thermostat.
Regards -

[john smith]

Thanks Creg
Yes, it is cooling the radiator.
When standing beside the car with both fans running (engine off), there is
an awful lot of hot air moving out of the engine bay.
This is a good sign that the fans are doing more than just cooling the
radiator.
If the fans are switched 'off' immediately the engine is shutdown then there
must be a large amount of residual hot air building up with no place to go.
It would certainly melt any snow accumulation on the bonnet!!!!

[lansdownplace]

I find the heat normally rises for a little while after the engine is turned off.

[Rubbond]

Peter is quite right - the fans should run on until everything has cooled
down sufficiently - with the ignition switched off - unless you want to sit
in the car for another10 minutes.
Rgds,
Andrew.

[Des]

This could be a relay at fault, power to fans via ignition controlled
relay, relay contacts have stuck together so now fans are powered always, not a
bad thing really, engine will get some heat soak preventing cooling once
stationary as cooling system will still have some thermo syphon effect,
this, and the nice blast of fresh air can only help prevent vapour lock
possibility. Disadvantages I can think of would be a flat battery if the fan
switch sticks on, or, in the event of an engine fire, could fan the flames.

[Rubbond]

Hi Greg,
Don't forget the water pump doesn't turn when the ignition is switched off!
You could end up with a big pool of coolant on the garage floor!
Rgds,
Andrew.