thermostat woes

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///Owen\\\ - 16 Jan 2006 01:32 GMT

I have a 89 Nissan truck, and was told I have a "lazy" thermostat. So I
took the old
one out (the spring side was pointing into the engine), put the new one in
and started up. I had the top of the rad open to add more coolant, and
noticed coolant running across the opening. My first thought was that there
shouldn't be any movement of coolant because the thermostat was shut.

My second thought was that the coolant was not only flowing, but flowing
AWAY from the thermostat. In other words the coolant was trying to push the
thermostat away from the engine block. I thought the coolant should push
the thermostat into the engine block - the flange keeps it out of course,
but the pressure of coolant seats the thermostat against the block..

Test drive - engine stayed cold

Help please

John

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Nate Nagel - 16 Jan 2006 01:39 GMT

> I have a 89 Nissan truck, and was told I have a "lazy" thermostat. So I
> took the old
[quoted text clipped - 14 lines]
>
> John

Your new thermostat is stuck open or installed incorrectly. Direction
of flow is correct. In a conventional radiator with top and bottom
tanks the top tank is the "hot" or "from engine" side.

nate

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Lawrence Glickman - 16 Jan 2006 01:49 GMT

>I have a 89 Nissan truck, and was told I have a "lazy" thermostat. So I
>took the old
[quoted text clipped - 14 lines]
>
>John

Dear John,

On any American vehicle I've worked on, the hot coolant leaves the
block through the tstat on the way to the top of the radiator. It is
helped along by the water pump. The water moves to the bottom of the
radiator where it hooks up with the water pump for recirculation.

So in my experience, the hot water coming from the engine is pushing
the tstat away from the block. And hot water from the engine comes to
the radiator by way of the upper radiator hose.

You say you have a Nissan. Can't speak to that particular vehicle. I
had a Fiat that was pretty screwy when compared with American
vehicles, so I can't rule screwy out in your situation, just show you
the way the American car makers do it.

Lg

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Nate Nagel - 16 Jan 2006 01:59 GMT

>>I have a 89 Nissan truck, and was told I have a "lazy" thermostat. So I
>>took the old
[quoted text clipped - 32 lines]
>
> Lg

should read, "used to do it." The trend now, esp. with crossflow
radiators, is to use "reverse flow" cooling systems where the water
cools the heads first, then the block. Supposed to keep the temperature
more even throughout the engine, and allow for higher compression (as
the heads run a little cooler.) But you are correct in that the flow
the OP describes is still what we would consider "conventional" flow.

The reason that originally radiators had the hot tank on top and the
cool tank on the bottom is that that is the natural direction that the
water would flow anyway. Remember the Model T Ford? Well, I don't
either, but it didn't have a water pump at all. It relied solely on
what they called "thermosyphon" circulation of the water, basically the
hot water rose to the top tank of the radiator, which was higher than
the cylinder head, and the engine drew in cool water from the bottom
tank of the radiator. For decades after that, cooling systems were laid
out that way because that was the way it had always been done.

nate

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Lawrence Glickman - 16 Jan 2006 02:42 GMT

>>>I have a 89 Nissan truck, and was told I have a "lazy" thermostat. So I
>>>took the old
[quoted text clipped - 32 lines]
>>
>> Lg

===========================================================

>should read, "used to do it."

Yes, I hesitate to make any generalizations anymore, with transglobal
manufacturing such that one doesn't even know where their car comes
from ( what country ), just where it may have been assembled.

Then again, different parts/modules come from different places, just
as the parts do. I have a Ford Stamping Plant here, about 10 minutes
away in Chicago Heights, where they bang out gas tanks and such. And
there are engine *assembly* plants up in Canada, and my car was bolted
up at Atlanta Georgia, and rail-shipped to Chicago. So who knows?

> The trend now, esp. with crossflow
>radiators, is to use "reverse flow" cooling systems where the water
>cools the heads first, then the block. Supposed to keep the temperature
>more even throughout the engine, and allow for higher compression (as
>the heads run a little cooler.) But you are correct in that the flow
>the OP describes is still what we would consider "conventional" flow.

It's the way it works on my Vulcan V6 anyhow. And any other car I've
owned, _except_ for the screwy Fiat from Italy and the Renault R8 from
France. When talking about Foreign Imports, all bets are off. My
money isn't on the table anymore, what little of it there is.

>The reason that originally radiators had the hot tank on top and the
>cool tank on the bottom is that that is the natural direction that the
>water would flow anyway. Remember the Model T Ford?

There are photos of that on the WWW. I have visited quite a few *car
museums* on the WWW and it is often more than worth the time.

> Well, I don't
>either, but it didn't have a water pump at all. It relied solely on
>what they called "thermosyphon" circulation of the water

Natural convection currents. Less dense water ( warmer ) rises and
floats on top of the cooler, denser, heavier water.

>, basically the
>hot water rose to the top tank of the radiator, which was higher than
[quoted text clipped - 3 lines]
>
>nate

I think it has a lot to do with tooling also. Who wants to switch to
a new and better design if it means throwing billions of dollars of
machining tools and castings into the garbage.

No doubt, somebody can build a better mouse trap, but Delorean aside,
who is going to make the investment? Already the car mfgrs. are
scratching tooth and nail to stay alive ( American car mfgrs.).
Laying off people left and right, closing down plants, stopping
certain models. BTW, I think the Sable isn't in production anymore.
I think I got the last one off the line ;-|

Lg

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///Owen\\\ - 16 Jan 2006 15:47 GMT

>I have a 89 Nissan truck, and was told I have a "lazy" thermostat. So I
>took the old
[quoted text clipped - 16 lines]
>
> John

Thanks, guys. I had a job keeping the new stat in the engine while I put on
the housing and tightened it up. The stat kept falling out. Perhaps it
never properly seated.

John

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