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From: HiC on 17 Nov 2007 08:00
'90 Supra with a 7MGE non-turbo. New fan clutch, radiator, thermostat,
water pump, fresh rebuild on the engine. Radiator and overflow tank
filled to correct levels.

After a few miles of running, the gauge shows it running well on the
hot side. However, when I turn it off and immediately restart, or even
just to the run position without starting, the gauge jumps back to
center and creeps back to the hot side. If it were running hot,
shouldn't the gauge jump right back to the hot side where it was?

From: EdV on 17 Nov 2007 11:04
On Nov 17, 8:00 am, HiC <brasspl...(a)yahoo.com> wrote:
> '90 Supra with a 7MGE non-turbo. New fan clutch, radiator, thermostat,
> water pump, fresh rebuild on the engine. Radiator and overflow tank
> filled to correct levels.
>
> After a few miles of running, the gauge shows it running well on the
> hot side. However, when I turn it off and immediately restart, or even
> just to the run position without starting, the gauge jumps back to
> center and creeps back to the hot side. If it were running hot,
> shouldn't the gauge jump right back to the hot side where it was?

In my experience, overheating engines would have some slight loss of
power and pinging sounds prior to reching the red zone. Do you
experience any of them?
From: Jeff on 17 Nov 2007 12:11
EdV wrote:
> On Nov 17, 8:00 am, HiC <brasspl...(a)yahoo.com> wrote:
>> '90 Supra with a 7MGE non-turbo. New fan clutch, radiator, thermostat,
>> water pump, fresh rebuild on the engine. Radiator and overflow tank
>> filled to correct levels.
>>
>> After a few miles of running, the gauge shows it running well on the
>> hot side. However, when I turn it off and immediately restart, or even
>> just to the run position without starting, the gauge jumps back to
>> center and creeps back to the hot side. If it were running hot,
>> shouldn't the gauge jump right back to the hot side where it was?
>
> In my experience, overheating engines would have some slight loss of
> power and pinging sounds prior to reching the red zone. Do you
> experience any of them?

In my experience, I have never really noticed a loss of power. The only
times I have noticed relatively less power was when I had a load of
people in my car or in a Toyota SR5 truck, I had a load of cylinder
heads in the back (17 if I recall). In both cases, I would estimate that
the weight of the load was about 2500 N (mass of about 250 kg - the
people included two kids). I also used to carry engines, speedy dry
(once when the truck had only 5th gear - the fork got bent), and junk
parts to the recycling center and other stuff - but what was different
these two was that I didn't expect lower acceleration to the extent that
it was.

Even when I load the car with books or other items, I don't really
notice less power. I just push the accelerator a little harder.

So, my question for Ed is, how much less power would there have to be to
really notice it? (In the above cases, the power was the same, just
lower acceleration because of the mass of the vehicle and what it was
carrying). I would think a slight loss of power would actually be a
significant loss of power.

Jeff
From: Hachiroku ハチロク on 17 Nov 2007 18:40
On Sat, 17 Nov 2007 05:00:22 -0800, HiC wrote:

> '90 Supra with a 7MGE non-turbo. New fan clutch, radiator, thermostat,
> water pump, fresh rebuild on the engine. Radiator and overflow tank filled
> to correct levels.
>
> After a few miles of running, the gauge shows it running well on the hot
> side. However, when I turn it off and immediately restart, or even just to
> the run position without starting, the gauge jumps back to center and
> creeps back to the hot side. If it were running hot, shouldn't the gauge
> jump right back to the hot side where it was?

Have you removed the bottom shroud?

From: Ray O on 17 Nov 2007 19:09

"HiC" <brassplyer(a)yahoo.com> wrote in message
news:8f351c6f-aba5-4471-a447-8ac7b7987e01(a)e4g2000hsg.googlegroups.com...
> '90 Supra with a 7MGE non-turbo. New fan clutch, radiator, thermostat,
> water pump, fresh rebuild on the engine. Radiator and overflow tank
> filled to correct levels.
>
> After a few miles of running, the gauge shows it running well on the
> hot side. However, when I turn it off and immediately restart, or even
> just to the run position without starting, the gauge jumps back to
> center and creeps back to the hot side. If it were running hot,
> shouldn't the gauge jump right back to the hot side where it was?
>
Several things can cause an engine to run hot. Check the coolant mix, make
sure the fan shroud and under-engine shrouds are in place, check to see that
coolant is actually circulating, check ignition timing. When the engine is
indicating hot, shut off the engine and see if the fan clutch is engaged.
If you replaced the thermostat yourself, make sure it is properly installed
(orientation of the spring and jiggle valve) and if you used an aftermarket
thermostat, make sure it is also properly seated.

Check the coolant temperature sensor voltage and associated wiring.
--

Ray O
(correct punctuation to reply)



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