4040Re: [bmw e28] heat inquiry #2
- Dec 11, 2005On Sun, 11 Dec 2005 19:35:49 -0800 (PST)
Guy DiCesare <guydicesare2000@...> wrote:
> My 88 535is has HOT heat while sitting stillSounds like you have 2 problems!
> which cools within seconds when I start driving. The
> blower motor has made intermittent noise for years but
> now the noise gets worse as I accelerate (but doesn't
> seem to have any decrease in output though).
1. Thermostat? If the motor gets hot while you idle, then probably the
thermostat is not opening or closing (whatever the case may be) properly.
It should automatically regulate the flow of coolant through the
radiator as needed. These little units are completely mechanical with
bimetallic pieces. They "wear out" or the metal gets tired over time.
It's a fairly easy DIY repair, but messy.
You also need to check the main engine fan. As the clutch within the fan
may not be working properly. But usually it's the opposite problem with
the fan though: that the clutch seizes, so the fan always runs full
blast, which makes the engine sound like a jet turbine! You can test
this (with the engine OFF, of course) by spinning the main fan blades
with your hand. It should not be very tight; neither, should the viscous
coupling be completely free.
Finally, you need to check the auxiliary fan and temperature sensors.
But they usually only come into play in extremely hot situations, i.e.
hot summer day, long highway drive, and then you slow down in
stop-and-go traffic suddenly. Engines do not like that! All the heat is
trapped in the motor. So the main fan with the assistance of the
auxiliary are supposed to get rid of the excess heat. There are little
electrical short circuit tests you can do, although I forget them off
the top of my head.
That the temp drops quickly suggests the water pump is OK and the flow
through the cooling system is uninhibited and the radiator is not
2. The cabin heater blower motor bushings or bearings wear out over time.
It sounds like a squeaky hamster wheel for a while. Sooner or later the
bearings will get so sloppy that the motor will shift and cage fans will
start to rub against the shrouds. The extra friction may cause the motor
to burn out.
This is an awkward repair. But still definitely DIY. If you're inclined.
Blake Nancarrow <blaken@...>
(sent via Becky!)
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