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7 Series - E65 / E66 (2002 - 2008)
Discussion of BMW's 4th generation E65/E66 7 Series flagship. The E65 generated much controversy, due to its radical styling and iDrive user difficulties. Nonetheless, the E65 broke records to become the best-selling 7-series iteration ever, especially after its 2005 facelift.

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  #1  
Old 09-07-2016, 09:09 AM
Romey-Rome Romey-Rome is offline
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Location: Seattle
 
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Mein Auto: 750li
Heater works - only until the car warms up

Once coolant temp is @ 105c, it starts blowing cold. It's ass backwards. No related codes.

Just did thermostat & upper hose and bled it. (for other reasons) It's first time trying to use the heater since the summer, so could just be a coincidence. Changed auxiliary pump last winter.

I guess heater control valve is still on the table, but I don't see how that would make sense in my situation. I mean, it's either clogged or it isn't...
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  #2  
Old 09-12-2016, 01:26 PM
InterpreDemon InterpreDemon is offline
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Location: Stamford, CT
 
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Mein Auto: 2003 530i
The HCV is normally open when de-energized. If you unplug it all the hoses should feel hot, if not you have a circulation problem. For example, if your water pump is weak the flow through the heater cores will be fine until the thermostat opens and flow is diverted through the radiator. Alternatively and more likely the auxiliary pump is bad or not functioning. I think its main role is to assure good flow through the heater cores once the engine is warmed up.
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Old 09-12-2016, 06:07 PM
Romey-Rome Romey-Rome is offline
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Thanks. My water pump is 1 year old, and the aux is even less. In & out on the HCV seem to be the same temp. Maybe my core is plugged up...
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Old 09-13-2016, 07:29 AM
InterpreDemon InterpreDemon is offline
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Yeah, but even more so than you said about the HCV, the cores would either be plugged or not... they wouldn't decide to be plugged whenever the engine temp gets to 105 or above. It's got to be something that changes when the thermostat opens up. The aux pump may be new, but that does not assure it is getting power or being turned on. Hopefully it's not the computer pulling a HAL 9000 on you... "I'm sorry Dave, I'm afraid I can't do that".
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Old 09-15-2016, 10:49 PM
Motronic Motronic is offline
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Heater valve clogged, cooling system has air in the heater core bc of that valve
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Old 09-16-2016, 09:19 AM
InterpreDemon InterpreDemon is offline
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Problem is, it works until the engine gets up to temp, so how did the air leave the cores, allow the warm coolant to flow in, then come back to the cores after the thermostat started opening?
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  #7  
Old 09-16-2016, 11:00 AM
Romey-Rome Romey-Rome is offline
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It has been working last couple of days. Maybe had to wait for the air to work its way through as I did a full drain before all this. Though I bled it enough I thought.
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Old 09-16-2016, 11:53 PM
Motronic Motronic is offline
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Quote:
Originally Posted by InterpreDemon View Post
Problem is, it works until the engine gets up to temp, so how did the air leave the cores, allow the warm coolant to flow in, then come back to the cores after the thermostat started opening?
Very very good question, I guess you didn't have much hassle with 105-110c high pressurized cooling system.

Simple, when it starts boiling, it will create air pockets in the cooling system and heater core is at the highest point. When it's cold, your aux water pump can push mostly bubble free coolant into the heater core, but when it starts boiling, and it is boiling at 110c if you have improperly sealed system.
The thing is, I saw tons of these overheating cars and heater valve construction isn't meant to last, it gets cooked inside due to very high temps, they made this engine run at.
Basically if you replaced heater valve and still ho hot air, it means you lose coolant pressure somewhere and therefore it starts boiling. At 110c any small tiny leak will make it boiling. If it was Toyota with 85-90c tstat, it wouldn't start boiling even with serious pressure loss or leak, just bc it runs cooler and tstat opens up earlier.
Bottom line- Bmw v8 doesn't like any tiny leaks unlike other cars where you can drive and add water for years
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Old 09-17-2016, 09:10 AM
InterpreDemon InterpreDemon is offline
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Location: Stamford, CT
 
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Makes sense, so the simplest quick check would be for him to have grabbed the rad hose and made sure the system was well pressurized... which is the other thing that happens when the engine warms up in addition to the t-stat opening. Agree on the use of plastics, in fact most of the stupidest and unnecessary problems you have with any newer BMW are due to the use of plastic... radiator tanks, valves, lower hose temp sensors, fuel level sensors, rear center brakes, not to mention washer spray heads and cup holders. That's one thing the Japanese seem to do far better than the Germans, perhaps due to their pioneering of plastic toys in the sixties.
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