On or around Tue, 18 Jul 2006 16:26:08 +0100, "Nige"
<
[email protected]> enlightened us thusly:
>Austin Shackles wrote:
>> On or around 17 Jul 2006 15:10:02 -0700, "ChavScum"
>> <[email protected]> enlightened us thusly:
>>
>>> agree - put the running hot down to old cars and inadequate
>>> maintenance. I've currently running a V8's auto Defender, with A/C
>>> and it doesn't twitch off 90 degrees celcius. It's not tricky and
>>> there's no need to sweat it out on a hot day.
>>>
>>
>> it's nearly always down to old radiators IME. There's really no
>> answer other than to replace 'em.
>>
>> I had this on the 110 V8 - tried various flushing stuff and
>> flushing it from the tap and reverse flushing and so forth, and
>> none of 'em had any effect, it'd still overheat when running slowly
>> uphill and suchlike, even with a fixed fan. New rad on it and it
>> never strayed above "normal" again.
>
>I had a look under the bonnet today after a long wait. The fan could easily be rotated with the engine
>off but still steaming hot. Shouldnt it be stiff or dopes that o0nly happen if engines running?
The viscous fan IME only starts turning for real when it's up near red on
the dial. It shoudl of course spin at startup for 20-30 seconds, easily
audile at road-going revs, and then spin down as the hub frees off. If
yours doesn't do that I'd suspect it. Worth noting that the bit of the dial
between the blue and the red (sometimes labelled "normal" is normal through
out the range - it only represents quite a narrow temperature range. ABOVE
normal is where "overheating" starts, i.e. into the red bit. Fitting
instructions for kenlowe suggest that you run it 'til the needle is pointing
about 3/4 of the way up normal (i.e. above common operating temperature),
then tweak the knob til the fan cuts in, then turn it back slowly til the
fan just cuts out.
so the cut-out temperature for the fan is slightly above normal, and the
cut-in is most of the way up to the red. The viscous fan should work much
the same - not doing much until it's needed.
diagnosis:
first, see that the fan pulls hard first thing in the morning, and that it
spins down after 20-30 seconds of say about 2000 rpm. You can check that
stationary with the bonnet open - if the fan's pulling hard, you'll be in no
doubt
If it doesn't do that, then I suggest replacing it anyway. If it spins but
doesn't spin down at all, then it's safe enough to use but reduces your
efficiency slightly.
next test: Try running the engine with the vehicle stationary (in D with
T-box in neutral for autos) at about 3000 rpm. Watch the gauge closely, and
listen for the fan spinning up - it makes a distinctive roar when pulling
hard, and more or less no noise when idling. If the temp pointer gets to
the bottom of the red without the fan spinning up, then I'd suspect it. If
it does that, don't just shut off - drive round gently to cool the motor
down a bit first... I reckon most of the damage due to overheating is down
to too-rapid cooling.
If you've got aircon, check the aircon fans if it has them, they too should
cut in (but possibly only with the aircon on). Not sure if P38s have 'em,
the classics definitely did - supposed to give extra airflow for when you're
idling with the aircon on.
Having said all that, BiL Tim had no end of bother with his 3.9 overheating
and in the end removed the aircon rad and decommissioned the aircon. Having
done this he fired up the engine and nearly got choked by the cloud of dust
and debris that got blown out of the engine bay. The aircon rad does
compromise airflow and thus cooling on the classic. again, don't know about
P38s.
--
Austin Shackles.
www.ddol-las.net my opinions are just that
"For when the One Great Scorer comes to write against your name,
He marks - not that you won or lost - but how you played the game"
Grantland Rice (1880-1954). my opinions are just that