engine cooling question

[coldtaco]

First, how does the engine coolant circulate when the thermostat is closed? Does it just go from block to interior heater back to block?
Next, is there any way of knowing when the thermostat is open?
Also, if you look at the picture below and the coolant hose with the yellow arrows, I have a secondary coolent temp guage coming off of this line. So, if I see temp on this secondary coolant temp guage does that mean the thermostat has opened? If this is correct, then that means that the thermostat basically never opens all winter long, even on 4hr road trips at 55mph.?? Is this bad or does it not make any difference? Just means I don't get too warm inside.

[Fantom]

As far as I know a thermostat has an operating temperature, this means that whatever make the unit is there is a factory spec for a limit on the temps when it opens. When closed the coolant just circulates through the engine, heater core(s) and into the lower section of the rad. When the temps reach the limit of the thermostat, it opens and the pressure sucks the coolant out of the top of the rad (where it is cooler) and mixes with the rest of the coolant already in circulation and assist in cooling the engine. As for your after market temp guage, it will tell you what temps the coolant is, more then likely it is going to give you about the same reading as you factory one. You'll know that the thermostat is not opening when you start to overheat. Even in cold weather the engine still reaches high operating temps and the thermostat still opens and circulates coolant, since the air outside is cooler, the engine will run cooler in winter then in the summer because the coolant in the rad is colder then in the summer. If you want it to be warmer inside, just turn your heater to recycle and it should be very toasty, unless your thermostat has been replaced by one with a very low temperature spec. they you'll also notice the engine temps running very low all the time.

[coldtaco]

Well, like I stated above, in the winter I don't get any temp readings on the second temp gauge. In the summer, or "warmer" temps, I will get reading on this second guage, but it also may drop to below the bottom, which I think is 100F. It will read the max that the thermostat is set at. So again, if I get temp reading on the second gauge, does that mean that the thermostat has opened?

[roscoFJ73]

Originally Posted by coldtaco

Next, is there any way of knowing when the thermostat is open?
.

My manual says to put your hand on the lower rad hose (careful) with engine running and after 5-10 mins you should feel the hose get noticeably warmer when it opens.
I tried it on my old 3F engine and it worked.

[coldtaco]

Rosco,
I don't think this will work with our temps. If you let it idle at 1200rpm all day long the water temp will hardly move, if any depending on the outside temp. When having it pluged in all day and then starting it up and letting it run for 5 min. before unplugging you will see a little more temp on the needle.

[roscoFJ73]

Originally Posted by coldtaco

Rosco,
I don't think this will work with our temps. If you let it idle at 1200rpm all day long the water temp will hardly move, if any depending on the outside temp. When having it pluged in all day and then starting it up and letting it run for 5 min. before unplugging you will see a little more temp on the needle.

I thought you would say that
Try some cardboard in front of the radiator or take the thermo out and put it on the stove in some water and watch a thermometer

I haven't experienced your low temps but I think the thermo should still open at 55mph on 4hr trips if its good.

[coldtaco]

Yeah, I got all that block the radiator and stuff. I even have the bottom of the engine compartment sealed off, to try and reduce wind chill factor and maybe store some engine heat when parked. Don't know how much this helps anything. How do you know if there are traped air bubles in the system? For the first time I have had temp showing on my secondary water temp gauge a couple of times since I installed the new thermostat. Anyone else got ideas to my original questions?

[roscoFJ73]

Im not familiar with the 13bt but normally the heater pipes would be the same temp as the engine coolant like they are in other LC engines.
This leads to another question. Does the heater have a good flow? They block up inside and impede the flow.

To get the air out of the system disconnect the heater inlet hose at the firewall end and open your heater switch.
This is the highest point of the coolant system so any trapped air should exit there. Top the coolant from that point
While your there you could backwash the heater element via the outlet heater hose. A lot of owners have reported these being full of crud,just stick the garden hose down there(you might have to thaw it 1st ).