circulation

[supraman508]

If the vacuum circulation is'nt working proper,could that interfear with the circulation of the radiator fluid traveling through the head and the heater core.I'm asking this because i had my system professionally flushed .afterwards i was driving through town and i did'nt have air for 2 minutes.i came back on and then the heat needle went all the way to 'H'.Then it proceeded to the middle normal range.The guy at the radiator place told me that i am getting no vacuum at the heater valve.so i had to re re-route a vacuum hose ,then i had heat.

 

[CyFi6]

not sure i completely understand but yes the heater core valve uses vacuum to actuate. If you dont have vac there, you wont get heat.

 

[supraman508]

not sure i completely understand but yes the heater core valve uses vacuum to actuate. If you dont have vac there, you wont get heat.

That makes sense.Someone told me to tie the heater valve open with wire or string.I tried that but did'nt work do to the heater core needed flushed.Know that it's been flushed i can tie the valve open now and it should work.Even after the radiator and the heater core has been flushed some of the antifreeze runs into the overflo.Does'nt make any sense.but what does:runaway:

 

[IJ.]

If it goes anywhere near the H it's way overheated due to the way our gauges read....

It might have been a one time air pocket thing but chances are it wasn't.

 

[CyFi6]

That makes sense.Someone told me to tie the heater valve open with wire or string.I tried that but did'nt work do to the heater core needed flushed.Know that it's been flushed i can tie the valve open now and it should work.Even after the radiator and the heater core has been flushed some of the antifreeze runs into the overflo.Does'nt make any sense.but what does:runaway:

Its supposed to, as the coolant heats up it expands and goes into the overflow at a specified pressure depending on your radiator caps accuracy. when the car cools down it sucks it back in

 

[jetjock]

^ Right. It's not about making sense. It's about science. The car uses what's called a closed pressurized cooling system, in contrast to open pressurized or non-pressurized systems of old. As such the radiator is always kept filled to the brim. Unlike open pressurized systems (in which airspace was left in the radiator for expansion) the radiator cap opens nearly every time the engine is run. Since liquids are incompressible the coolant has to have a place to go when it expands and that place is into the overflow.

When the engine cools a vacuum valve in the radiator cap opens and draws coolant back to keep the radiator filled to the brim. Next time you have the cap off look at the bottom and you'll see this little vacuum valve. It'll be either spring loaded or weighted. It really doesn't matter but the as long as the cooling system is clean the weighted type is preferred.

For the system to work the overflow plumbing must be airtight all the way from the radiator neck (including the upper seal on the rad cap) to the suction screen in the overflow tank. Many people ignore this little bit of plumbing. Don't. Finally, although many people do it, the radiator cap on such systems is not supposed to be be routinely removed.

 

[CyFi6]

Jetjock, while we are on this topic i have had a problem with the stock radiator in my na 7m. It seems theres a large area at the top of the tank that is filled with air, when i squeez the upper hose i can hear coolant sloshing around in the upper tank, but wheni remove the cap coolant is up to the top, like theres a high spot in the radiator where air is stuck, ive tried burping it with the special funnel and going on a steep slope but nothing does it. The car also does not seem to spew much if any into the overflow tank, im assuming because of this air.
edit, it has a new thermostat and a new radiator cap rated at 13psi

 

[IJ.]

The recovery fitting in the neck should be the higest point in the cooling system so if it's all functioning correctly it "should" self bleed once the Rad is filled with the Heater on.