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post #1 of (permalink) Old 12-30-2004, 07:06 PM Thread Starter
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venting the coolant system

I need to replace my thermostat (stuck open). I've got a 258 (4.0 head - not that it really matters), so the thermostat is on the top front of the head. I also have a heated intake. The connection pattern for the heater loop is:

pump to heater core (upper)
heater core (lower) to intake (rear)
intake (front) to thermostat housing

I don't know if the hoses for a v-belt system are significantly different, but the high point in mine (serpentine) is right in the middle of the upper radiator hose. What is the best way to refill the system, purging/venting as much air as possible? Does getting as much air out as you can really matter - in other words, does the system do a good job of venting itself? If it does, how does it push the air out and pull water in? I realize the overflow tank is there for expansion/contraction, but I don't get how it would help get air out (if it does).

Also wondering which way the coolant flows... does the pump push water into the engine or pull it out?

highfill is offline  
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post #2 of (permalink) Old 12-31-2004, 07:55 AM
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Re: venting the coolant system

[img]images/graemlins/smile.gif[/img] The coolant flows from bottom to top in most systems. That is to say that the radiator cools the falls to the gravity feeds to the intake side of the water pump.....and the pump PUSHES it through the system. In my 1952 John Deere tractor, the coolant moves all by water pump...and that is called a percolator coffee pot. Auto engineers have just made the thermo-siphon system better by having a pump to scoot the water along overcome the high spots. My John Deere would not work if there was a high spot anywhere. [img]images/graemlins/tongue.gif[/img] What you need to do is BE SURE that you drill a hole in that thermostat before you install it. Not much of a hole, just the size of the lead in your pencil is enough. That hole will help the engine BURP better when you are filling it and when it is just starting up, and it will help the coolant temps be more level as the engine warms spikes. Modern systems are made to run with no air in them at all....just liquid...and it takes a little doin' to get all the air out. After you have driven it some, expect the level in the coolant tank to drop as the air in the system is "burped out" and then replaced by liquid when the engine cools down and slurps liquid back in from the coolant tank. Add coolant as needed to get to the correct line. Be sure that you fill it when the engine is cold so you know how much to add. [img]images/graemlins/tongue.gif[/img] The flow is actually from thermostat housing to the intake manifold heat jacket-to lower heater core fitting-out of upper heater core fitting to water pump fitting. The thermostat housing is the high pressure side of the pump circuit, the lower fitting next to the lower radiator hose is the suction side of the pump. [img]images/graemlins/tongue.gif[/img] Hope this helps you get things straight in your mind. [img]images/graemlins/smile.gif[/img] I'm kind of busy right now or I would go to Tennessee and help you just to see what Tennessee looks like. [img]images/graemlins/smile.gif[/img]
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