It is most likely your electric auxilary heater pump has failed.

Tiger wrote:

Why would you suspect that as most likely? AFAIK, the aux pump on
most models is there to provide faster movement of hot water at idle.
The usual symptom is lack of heat at idle/low speeds, good heat at
highway speed, isn't it? On 116, the pump is disabled once the cabin
air comes up to temp and I've seen lots of folks here with various
models report eliminating/bypassing aux pumps and noticing little
difference.

On 190E, aux pump acts both as a pump and heater valve. On other models,
they are mostly mechanical pump that is next to the main waterpump which is
essentially a full time pump.

At high speed, the water pump is at full force but the nature of water or
air... always travel the easiest route. Since heater hose is more
restrictive, less flow which means less heat.

That flap is vacuum operated. If there is no vacuum to the yellow checkvalve
by your master cylinder, it will default to defrost... which is 100% heat.

Could it be the heater core. I flushed it and it improved. Is there a
better way to flush it? As far as the auxiliary water pump, should I
disconnect it and see if there is a difference. I do hear/feel
vibration at the outlet of the auxiliary water pump and hose going to
the heater core.


Tiger wrote:

I changed the thermostat last year with no improvement.

Could it be the heater core. I flushed it and it improved initially.
Is there a better way to flush it?

As far as the auxiliary water pump, should I disconnect it and see if
there is a difference. I do hear/feel vibration at the outlet of the
auxiliary water pump and hose going to the heater core.


T.G. Lambach wrote:

Take the pump off the car... and rig it up to a hose in bucket and see if it
pumps water out.

Reverse flushing the heater core is the best... rig up something so you can
hook up your garden hose to it... and other end free or into a hose to out
of engine area.

What about the heater core. Could it be beyond flushing based on the
age of the car? Have you ever seen these heater cores replaced and the
heat improves?



Tiger wrote:

Yes... if someone filled the radiator with quick sealer... that definitely
would cook the heater core... render it useless.

"Tiger" <tiger0002 (AT) hotmail (DOT) com> wrote

...any easy way to fix that ??