740il over heating !

Hello to all, please help . i have a 1998 740il , the upper raiator hose gets verry hot , but the lower radiator hose stays cold ! when i remove the radiator cap, and rev up the engine i see
that colant rush in the tank , is this meansthe water pump is good? i is this a stuck termostat , please advise how to replace. many thanks Fredwash @aol.com
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On Thu, 05 Oct 2006 11:08:52 -0700, fred740il wrote:

this is generally indicative of a spent thermostat.
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How do you figure that? If the coolant flow in the radiator reacts to revving the engine, doesn't that mean the thermostat is open?
Just curious.
Eisboch
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Could be a dead water pump. when the plastic impeller and metal shaft part company it might still drag the fan along and cause some flow. But not enough for proper cooling.
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Email: snipped-for-privacy@unixnerd.demon.co.uk, John G.Burns B.Eng, Bonny Scotland
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John Burns wrote:

Does the 740i V8 engine use a plastic impeller on its waterpump? I thought that mishap was limited to the "small six?"
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No, the V8s do it too. At least in the early years.
--
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Email: snipped-for-privacy@unixnerd.demon.co.uk, John G.Burns B.Eng, Bonny Scotland
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Thank you all , may be that why when i rev the engine i see the water flow to the expantion tank ! i have to start from somewhere, i am going to replace the termostat and then see ! next is water pump or radiator ? i just hate to repalce all . i have done the cooling system bleeding . i will let you all know the findings . Regards Fred740iL John Burns wrote:

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On Fri, 06 Oct 2006 08:38:02 -0400, Eisboch wrote:

It is my understanding(limited as that may be :) ) that the thermostat functions as a "door" based on temperature. If the thermostat is stuck closed then the coolant will not be able to flow through the radiatior, cooling the engine. Thereby giving you a very hot upper hose, and a cool lower hose. All the hot stuff stays blocked up by the faulty thermostat.
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no one wrote:

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Thanks for your advised , i am going to replace the termostat this afternoon and post my finding for all E38ters .Oh this realy works ( PIXEL restoration instructions-for MID speedo/tach ) i have done that, but be more carefull that i was ( bent the temp gauge nidelle) here ....http://bimmer.roadfly.com/bmw/forums/e38/forum.php?postid 70167&page=1
good luck to all Fred740iL no one wrote:

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HI again , in this 740 even when engine is cold and termostat closed , there is small flow to the expantion tank. i did replaced the termostat and upper radiator hose , after runing the engine for about 20 min, finaly the lower radiator hose start to warming up , but now i don't get much heat from heater even the engine temp is in the midel ! what is next that i have to do , repalce the water pump or radiator ? can any one tell me in order to bleed the radiator , engine must be warm or cold ( open termostat or closed ? ) , thanks Fred Eisboch wrote:

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