95 Eldorado ETC - Cooling system
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Northstar Engines and System Technical Discussion Discussion, 95 Eldorado ETC - Cooling system in Cadillac Engine Technical Discussion; I am trying to figuire out the direction of coolant flow through the radiator. I noticed the thermostat is connected ...
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    mem54 is offline Cadillac Owners Member
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    95 Eldorado ETC - Cooling system

    I am trying to figuire out the direction of coolant flow through the radiator. I noticed the thermostat is connected to the lower hose. Which way does the coolant flow? Thanks.

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    Ranger's Avatar
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    Re: 95 Eldorado ETC - Cooling system

    It flows the opposite of most engines. Flow is from the engine through the stat and to the radiator. This keeps the engine temps consistent rather than bringing cool coolant into a hot engine.

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    Re: 95 Eldorado ETC - Cooling system

    Most of the warmup time, because the thermostat is at the engine end of the return hose, the radiator is not even in the cooling circuit. You'll notice that the thermostat wax pellet and spring are on the water bypass side of the thermostat housing. Start the car and all coolant flow is confined to the engine, bypass, crossover, and heater circuit. As the engine coolant returning through the bypass warms to 188 the thermostat begins to open, and small amounts of coolant from the "radiator side" of the system begin to bleed into the engine side but not enough to close the thermostat. As the engine warms further the thermostat opens further (normally about 60%) and then there's high coolant flow in the engine side and low to moderate flow in the radiator side. This holds true even in summer with the A/C on because then the fans run in slow, and the temperature stays about at 12:00 on the gauge (~196 degrees). Turn OFF the A/C, the fans stop, and are then controlled by the temp sensor circuits/PCM to come on in slow at 224 degrees, fast at 236.

    The older system, in which the thermostat sits in the top of the intake manifold water outlet, uses a bypass system to heat the block and heater circuits, BUT, when the coolant hits thermostat temps the thermostat opens, allowing a cold slug of coolant from the radiator to enter the water pump, then block, then heads. The cold slug cools the thermostat which shuts, and the cycle repeats over and over until the entire system reaches equilibrium.

    The Northstar system eliminates the cold slugs of coolant in the system and assures a constant, even flow of coolant to the water pump which eliminates cavitation and aeration of the coolant which could cause hot spots. It also warms the engine and heater much faster than a conventional system.

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    Re: 95 Eldorado ETC - Cooling system



    Quote Originally Posted by Ranger View Post
    It flows the opposite of most engines. Flow is from the engine through the stat and to the radiator. This keeps the engine temps consistent rather than bringing cool coolant into a hot engine.
    I think you may have it backwards. When the temp gets high enough to open the thermostat, the waterpump sucks coolant out of the bottom radiator hose, through the stat, and pushes it through the engine. This is why there is a metal spring in the bottom hose: to keep it from collapsing from the suction.

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    Re: 95 Eldorado ETC - Cooling system

    No, read Subs post. The stat is on the return line so cooled water does not slug the engine. Just the opposite of most. They wanted to keep the aluminum components as stable as possible temperature wise.

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    Re: 95 Eldorado ETC - Cooling system

    If you search the hose racks at any parts house you'll find that the great percentage of "lower hoses" has a stainless steel coil spring insert OR a reinforced wall: ALL "lower " hoses are subject to some or great water pump suction, particularly when the thermostat is still closed and the engine (any engine) is warming up in the bypass loop mode. In a conventional cooling system the coolant "wants" to take the path of least resistance - out the upper hose, through the radiator, and back through the lower hose. In the Northstar, with its unique bypass and thermostat location, the path of least resistance is the engine/bypass/heater circuit and only enough coolant is bled through the radiator to maintain temperature. BUT, similar to a conventional setup, when engine coolant temperatures exceed the thermostat "wide open" setting the system changes to almost full flow through the radiator.

    Hard to envision, but this is NOT your average cooling system.

    Someone's gonna say "But centrifugal pumps don't have suction." Not so: When a centrifugal pump (automotive water pump) is not airbound it has a good deal of inlet suction and can "lift" liquids a fair distance. It's cavitation and air intrusion, as in: dry running from loss of coolant or system pressure, that stops a centrifugal pump dead.

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    Re: 95 Eldorado ETC - Cooling system

    Quote Originally Posted by Ranger View Post
    No, read Subs post. The stat is on the return line so cooled water does not slug the engine. Just the opposite of most. They wanted to keep the aluminum components as stable as possible temperature wise.
    I think we're both on the same side, explaining the same things in different ways.

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    Re: 95 Eldorado ETC - Cooling system

    Kind of what I thought.

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