heater blowing cold air... E38 95 740i

the heater just started blowing cold air one day last week. And never return to blowing hot even after car is warmed up and is running for 30min or more..

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On Fri, 16 Nov 2007 21:54:01 -0800 (PST), snipped-for-privacy@gmail.com wrote:

Have you checked the coolant level?
Usually due to low coolant due to a leak - usually from the thermostat housing (plastic) that cracks and weeps coolant when hot or under pressure.
Hugh
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Two possibilities.
1. The water pump impeller is losing its blades, and water does not circulate well. BMW (actually, all automakers) is known to use water pumps that have plastic impellers. The impeller blades wear down due to the corrosive effect of heat and friction. When this happens, circulation through the engine cooling system and through the life support (heater) systems are affected.
2. The heater core or the plumbing system leading to/from it are clogged. Warm coolant from the water pump is routed through a (roughly) 3/4 inch hose to the heater core that is housed inside the cabin of your car. BMW likes to put this unit in the center console. If the hose leading to the core, the core itself, or the hose leading back to the engine, is clogged for any reason, circulation will be compromised, and you will get cold air from the life support system.
Another possibility is that the control for the system has taken a bye.

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And there is the WORST possibility,:
3. The heater core is plugged with fragments from the water pump impeller.

Does the E38 have a real temperature gauge or is it new enough to have the fake gauges? --scott
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"C'est un Nagra. C'est suisse, et tres, tres precis."

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On 19 Nov 2007 10:30:05 -0500, snipped-for-privacy@panix.com (Scott Dorsey) wrote:

Mine seemed to function as a normal electric gauge would however my new E65 has real fake gauges (gages) or rather a red lit rim on the rev counter almost showing one not to rev that high when cold.
Other than that no gauges on the new one in any shape or form.

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I'm not certain what the "red lit rim" is all about, but if it is a warning about over-revving the motor then there is not a qualification as to the temp of the motor. Red Line is a limit, whether the engine is hot or cold. Hitting Red Line on a cold motor is a serious mistake that one should take extra precautions to never do. In my book, hitting Red Line on a warm motor is bad practice that one should avoid as part of a normal driving experience.
Having said that, the OP was asking about the ventilation system, and this system does not care what the indicated temperature is.
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Some have variable redlines depending on the temp of the engine, so in the abscence of a real temp gauge this is the best you have. His was a comment about how to tell if the car is warmed up or not. He's talking about the rim around the speedo.
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wrote:

Thank you my friend. The poster above obviously did not engage their brain before opening mouth.
If he had read what I wrote instead of picking the words REV - Temp and putting them in the same sentence he might have understood what I said. However, if he has NEVER looked at a new BMW then he is probably ignorant of the new designs and functions.
Yes my friend no real gages (gauges) just life sized photographs!
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My confusion comes from your discussion of new cars when the topic is a car that is at leaszt 13 model years old and has not got the display features you are talking about.
Part of intellilgence is knowing when to inject new topics to a discussion, and when to keep to the topic at hand ...
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Jeff
The topic went from real temp gauges to those that looked real but were the forerunner of the type we now have. Is it a real gauge or just a life sized photo'?
Whatever temp indicator he has it might be a good idea to get the actual temp checked. I used to use an old oven thermometer I stole from a scrap dealer - very handy as it was a real one with copper tubing and all. Quite accurate too especially for checking coolant temp and thermostat open points but probably a bit difficult now that there are no filler caps on the top on the radiator.
Hugh
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