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Old 01-13-2010, 06:39 PM   #1 (permalink)
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Why do taurus' have a heater bypass line? Why is it there? and what is it's main function? Is it simply incase the heater core plugs up? If so why does it not have a PSI relief valve in it?
It has been bugging me. some one help...
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Old 01-13-2010, 07:32 PM   #2 (permalink)
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QUOTE (tonyrader @ Jan 13 2010, 07:39 PM)
Quote:
Why do taurus' have a heater bypass line? Why is it there? and what is it's main function? Is it simply incase the heater core plugs up? If so why does it not have a PSI relief valve in it?
It has been bugging me. some one help...[/b]

I bypassed a leaking heater core on wife's Y2K Taurus several years ago. Went from thermostat end of Vulcan via the two temperature sensors with a long piece of heater hose, directly back into the connection on the water pump. That connection feeds returned, heated coolant into a low pressure area behind the impeller.

The bypass is always transporting warmed/heated coolant from the 'hot' end of the motor back to the water pump. In the original configuration, it is moving the first warmed/heated water via the heater core long before the thermosat starts to open. Helps to warm the cabin, a skosh sooner.

Long story, but shorted, to say the bypassed fluid wants to first and always be passing by the temperature sensors near the 'hot' end of the motor.

J
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Old 01-21-2010, 11:29 AM   #3 (permalink)
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Joepa, I believe you did not get it quite right. And I have a similar question as tonyrader.

Why the heater core has a bypass? Factory installed hose that let the water flow avoid going through the heater core.
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Old 01-21-2010, 11:56 AM   #4 (permalink)
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Return line from heater core feeds coolant to the bank 1 head. Plugged core = little/no coolant flow to bank 1 head = overheating, cracked head, blown HG, etc.
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Old 01-21-2010, 07:03 PM   #5 (permalink)
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There's no doubt it's a "kludge" fix by Ford to save themselves from being sued by thousands of customers with cracked engine blocks. They knew the heater cores would plug up, so they put in that parallel branch to make sure there would always be flow even if the core was completely blocked.

I think the bypass hose was installed under a TSB.
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Old 01-21-2010, 08:22 PM   #6 (permalink)
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[quote]
There's no doubt it's a "kludge" fix by Ford to save themselves from being sued by thousands of customers with cracked engine blocks. They knew the heater cores would plug up, so they put in that parallel branch to make sure there would always be flow even if the core was completely blocked.

I think the bypass hose was installed under a TSB.
[/quote


With my own two mitts, just finished replacing both Vulcan heads with rebuilds. If a feller looks at the coolant coursing through the motor, as a result of the pressure generated by the waterpump, flow is EVENLY distributed left and right upon exiting the pump, into each side of the front of the block, below each head. The coolant then EVENLY pressurizes each side of the block in the vicinity of the cylinder walls. This same coolant moves upward toward each head and is EVENLY restricted by the small holes in each head gasket. Once inside each head, coolant continues to pickup heat and move EVENLY towards the rear of each head, then via passages of EQUAL size up and into the lim. Here the coolant flowing from each head joins up in the cavity behind the thermostat. An accurate temperature reading of coolant leaving each head at this time would be interesting. I'm betting on a healthy motor, the two temps would be mighty close.

The above presumes a decent flow of warming coolant by the thermostat, which will cause it to allow hot coolant to move to the radiator inlet. If no coolant is being bypassed back to the waterpump low pressure area, coolant temps in the area of the thermostat will seriously lag the need for thermostat opening. The hot area in the thermostat cavity is an ideal location to sense temps needed for the gages and computer. With the bypass presenting a good, hot, flow sample for the thermostat, place the temp sensors for the gage/computer in the same stream.

I have doubts about the Vulcan ever having a problem with even coolant flow throughout each side of he motor. Why the heater core itself was bypassed, was to guarantee the thermostat and the two temp sensors a failsafe working sample of max hot coolant. A plugged heater core would prevent this, without the bypass arrangement around the core. Quick and dirty fix.

YMMV, J
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Old 01-21-2010, 08:56 PM   #7 (permalink)
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Just being an ass because I did Hydraulic Design for several years but Pumps do not create pressure. They create flow.
restrictions creat pressure. Restrictions also create heat.

Just sayin

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Old 01-21-2010, 10:21 PM   #8 (permalink)
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Many other cars/trucks have them, too. I know GM's full size cars in the 80's also had them, for the same reason our cars have them.
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Old 01-22-2010, 01:39 PM   #9 (permalink)
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Nowadays, the heater core is a part of the regular coolant circulation whether cold or hot. If the heater core is completely clogged and there's no bypass, there is no coolant circulation at all. Then the engine will overheat. So under this type of design, I don't see how you can NOT have a bypass hose.
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Old 01-23-2010, 09:35 AM   #10 (permalink)
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QUOTE (yiranhu @ Jan 22 2010, 01:39 PM)
Quote:
Nowadays, the heater core is a part of the regular coolant circulation whether cold or hot. If the heater core is completely clogged and there's no bypass, there is no coolant circulation at all. Then the engine will overheat. So under this type of design, I don't see how you can NOT have a bypass hose.[/b]
That's what I (a non-mechanic) always thought (at least with my Taurus), but JOEPA seems to indicate that this is not the case. He says the bypass "guarantees a sample of max hot coolant" to the temperature sensors.

Is this a matter of semantics here?

If I remove the bypass hose and revert back to just the hoses going in and out of the heater core (with no parallel branch), what will happen?

The heater core will block up completely and then what?

JOEPA says that coolant will continue to flow through the engine but: "coolant temps in the area of the thermostat will seriously lag the need for thermostat opening"

I don't get this part.

He seems to say the bypass hose is not needed for coolant circulation - that the coolant courses through the block regardless. But then he says the coolant near the temp sensors does not get hot enough to open the thermostat often enough.

If the thermostat is not opening often enough, doesn't this create an increased risk of overheating (and/or a cracked block)?

And how does the coolant (still coursing through the block even without the bypass hose) not get hot enough to open the thermostat often enough if it isn't coursing though the radiator? Wouldn't this coolant open the thermostat MORE frequently, rather than less frequently???

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