On demand cooling fan in GS300 MK-I?

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John Smith - 20 Aug 2006 01:33 GMT

With many if not most cars, I can hear a temperature controlled cooling
fan start to run when I stop the car and switch it off. It continues to
run for a little while. As far as I know, that is meant to ensure that
the engine can slowly loose its heat after being stopped, because there
is no longer air passing past the radiator (due to no movement) and the
water pomp has stopped (due to the engine being stopped. This of course
is all good and well and makes sense. However, I cannot remember having
heard this on my 1995 GS300. AT least not for the last couple of years
and perhaps not ever in the last 8 years that I have had it.

Does this car not have any temperature controlled auxiliary fan? Does it
not need it?

I remember once or twice on really hot days, after a lot of stop and go
city traffic, hearing the radiator (or expansion vat, didn't open the
hood) actually boil after parking the car. That does not sound like it
should be that way either.

Or is there perhaps a problem with a fan or sensor that is not
functioning? No warning or CEL light and the temp gauge is always at
just a notch below middle.

Thanks in advance for any insights.

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Ray O - 20 Aug 2006 03:30 GMT

> With many if not most cars, I can hear a temperature controlled cooling
> fan start to run when I stop the car and switch it off. It continues to
[quoted text clipped - 19 lines]
>
> Thanks in advance for any insights.

The electric cooling fan on the GS 300 does not run if the engine is not
running.

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Ray O
(correct punctuation to reply)

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John Smith - 20 Aug 2006 04:17 GMT

>> With many if not most cars, I can hear a temperature controlled cooling
>> fan start to run when I stop the car and switch it off. It continues to
[quoted text clipped - 22 lines]
> The electric cooling fan on the GS 300 does not run if the engine is not
> running.

Thanks for your reply. Your answer is definitely clear. Is there no risk
of the engine overheating when the water pump stops while the cooling
fluids are still very high?
And I do wonder however what I should do whenever (if ever) I do
experience boiling cooling fluid. Mind you, that has only happened two
times in the past that I can recall, both times after a lot of stop and
go traffic in the city, during very hot days. And that was before
replacement of the radiator, that had been on its last legs for a while
too, so that might have already been clogged up.

Thanks in advance!

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John Smith - 20 Aug 2006 04:22 GMT

> Thanks for your reply. Your answer is definitely clear. Is there no risk
> of the engine overheating when the water pump stops while the cooling
> fluids are still very high?

When the temperature of the fluid is still very high, is what I meant to
write, of course...

> And I do wonder however what I should do whenever (if ever) I do
> experience boiling cooling fluid. Mind you, that has only happened two
[quoted text clipped - 4 lines]
>
> Thanks in advance!

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Ray O - 20 Aug 2006 05:15 GMT

>>> With many if not most cars, I can hear a temperature controlled cooling
>>> fan start to run when I stop the car and switch it off. It continues to
[quoted text clipped - 26 lines]
> of the engine overheating when the water pump stops while the cooling
> fluids are still very high?

I suppose that in theory, the engine can overheat after the engine is shut
off, but I have never heard of it happening in a Lexus.

> And I do wonder however what I should do whenever (if ever) I do
> experience boiling cooling fluid. Mind you, that has only happened two
[quoted text clipped - 4 lines]
>
> Thanks in advance!

The cooling system is pressurized so you should not be able to hear boiling
coolant. If you can hear the coolant boiling, then there is air in the
system and/or the radiator or radiator cap is bad. If the system is
operating properly, after the engine is shut off, some coolant would
circulate by convection and if the coolant is heated, it would expand and
move into the overflow vessel. As the coolant cools down, the coolant is
sucked back into the radiator from the overflow vessel.

Signature

Ray O
(correct punctuation to reply)

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John Smith - 21 Aug 2006 02:15 GMT

>>>> With many if not most cars, I can hear a temperature controlled cooling
>>>> fan start to run when I stop the car and switch it off. It continues to

>>> The electric cooling fan on the GS 300 does not run if the engine is not
>>> running.

>> Thanks for your reply. Your answer is definitely clear. Is there no risk
>> of the engine overheating when the water pump stops while the cooling
>> fluids are still very high?
>
> I suppose that in theory, the engine can overheat after the engine is

shut

> off, but I have never heard of it happening in a Lexus.
>
[quoted text clipped - 8 lines]
>
> The cooling system is pressurized so you should not be able to hear

boiling

> coolant. If you can hear the coolant boiling, then there is air in the
> system and/or the radiator or radiator cap is bad. If the system is
> operating properly, after the engine is shut off, some coolant would
> circulate by convection and if the coolant is heated, it would expand

and

> move into the overflow vessel. As the coolant cools down, the

coolant is

> sucked back into the radiator from the overflow vessel.

Well, like I said, I do know that my radiator was on the way out already
when that happened, so that will account for the boiling. Since the rad
was just replaced (with timing belt which was ready to be replaced and
thus water pump and serpentine while they were there anyway) I don't
expect it to happen again. Thanks for your info. It is always a pleasure
to read your comments and well founded insights here.

Cheers!

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Ray O - 21 Aug 2006 04:08 GMT

> >>>> With many if not most cars, I can hear a temperature controlled
> cooling
[quoted text clipped - 45 lines]
>
> Cheers!

You're welcome and thank you for your kind words!

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Ray O
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