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..
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.
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.
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.
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?
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.
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.
Natural convection currents. Less dense water ( warmer ) rises and floats on top of the cooler, denser, heavier water.
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 ;-|
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.
MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.