Is it safe for the engine to turn off the recirculating pump?
 

Hi,

from the diagram below the recirculating pump supplies heated coolant for cabin heating and for heating up windshield water.

Because of a leak in this circuit leading to loss of coolant I want to electrically shut down the recirculating pump temporarily until the leak is fixed.

I understand that there will be no heated windshield water and no heat for the cabin, which I can live with.

The main question is whether the engine cooling is affected causing damage to the engine itself?

Thanks for bearing with a possibly dumb question but I was goofy enough to break a connecting pipe of the above circuit (part #23)!

http://s245.photobucket.com/albums/g...Connection.jpg

I answered this "over there" as well...

It is safe. The pump is only required for the REST feature, and not for engine cooling. It helps with cabin heat, but is not required.

Unlikely
 

I have no direct experience, but it looks like a clear case to me:
As long as there is no loss of coolant there is no problem.
Engine cooling does not rely on heat radiation by the heater (if so, all engines would overheat in summer). I would proceed. If the leak is stopped by disabling the pump (there might still be coolant flow in the heater circuit due to convection) I would not worry.
Good luck, Bruno

The reason I asked because I plugged hose #5 but as the pump is active and presses coolant thru the not leak-proof makeshift plug I needed to stop and fill-up with coolant this morning during my drive to work.

Thanks for easing my mind and have a good day.

you just wont get heat at idle, or lower heat I should say

If you shutdown recirculating pump still flow will be in these lines. The pump speed up process of heating the car when is cold. The monovalve controls the flow but pressure is in the system. You need to block flow completely on both side of heating circuit. Where are you in Dallas maybe we are the neighbors? Give me a call 214 5370625. Good luck

Thanks!
PM sent!

In addition to providing hot coolant for correct heater operation, the auxilliary pump is also meant to assist engine cooldown. See following text taken from MB literature. If your engine sees high temps, you could be risking damage. See the Engine OFF Cooling section in particular...

PURPOSE
The coolant circulation pump is arranged in the return circuit to provide constant coolant flow through the heat exchanger during heating operations.

OPERATION
When a heating function is selected, the climate control unit energizes the coolant circulation pump continuously. When the control unit determines that heating is no longer required the pump is switched of.

Engine OFF Cooling :

At engine coolant temperatures greater than 100 °C, the coolant temperature is monitored for 90 seconds after switching off the ignition.
If the coolant temperature exceeds 110 °C after 90 seconds, the coolant circulation pump (A3lml) is switched on for a maximum of 10 minutes to assist in cooling the engine. Should the coolant temperature drop below 110 °C during the 10 minute period, engine OFF cooling switches off.
During engine OFF cooling:
Coolant circulation pump (A31m1) is ON,
Coolant pump control relay (K30) is energized,
Blower motor (A32m1) is OFF,
Left and right duovalves (A31y1, A31y2) are closed, thereby opening the bypass for engine OFF cooling.

Thanks, what is the source of such hidden information? Could you be more specific than just "MB literature"?

The owner's manual is definitely very superficial.

Hi pcmaher,

I visited your page and am very very impressed, especially this one on restauration of duavalve.

http://v12uberalles.com/Rear_AC_System.htm

Profound knowledge and great skill. My kudos!

Thanks for your kind words! The info I posted is from Alldatadiy.com. They sell subscriptions to the info. They have MB literature, test procedures, recalls, instructions, etc online. There are links to Alldatadiy.com on my webpage. I've found it tremendously helpful.